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life",3,7,[37,124],{"id":38,"data":39,"type":25,"version":41,"maxContentLevel":34,"summaryPage":42,"introPage":50,"pages":57},"3b912d6a-5cfc-4a04-8c16-2ebaa0239693",{"type":25,"title":40},"Introduction",4,{"id":43,"data":44,"type":34,"maxContentLevel":34,"version":24},"5085765f-769e-425a-b299-c6761005257c",{"type":34,"summary":45},[46,47,48,49],"Aristotle's life definition includes self-sustenance, growth, and decay.","Fire challenges Aristotle's definition of life.","Viruses blur the line between living and non-living.","Evolutionary change complicates defining life.",{"id":51,"data":52,"type":53,"maxContentLevel":34,"version":24},"392aff41-02ae-4321-9595-cc1312a60a6b",{"type":53,"intro":54},10,[55,56],"Why does fire complicate Aristotle's definition of life?","What makes viruses a tricky case in defining life?",[58,76,93,119],{"id":59,"data":60,"type":24,"maxContentLevel":34,"version":25,"reviews":63},"4875dc0c-5cf4-419a-8538-635241857a98",{"type":24,"markdownContent":61,"audioMediaId":62},"\"Life is marked by the ability to nourish oneself, grow over time, and eventually decline.\"\n\nAccording to the Greek philosopher Aristotle, this is the definition of life. In other words, life is the capacity for self-sustenance, growth, and decay. His definition captures the cyclical nature of being alive on planet Earth.\n\nBut when we try to put this definition to the test, we quickly come across problems.\n\nWhat about fire? — we might ask. Doesn’t fire sustain itself with oxygen, grow, and die out?\n\nBack to the drawing board.\n\n![Graph](image://3aa166d4-80d6-430c-a5df-fa70e381751a \"\\\"Fire\\\" by MarcusObal (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")","9913b258-c46e-4b90-a1ac-b8e413bbb37f",[64],{"id":65,"data":66,"type":67,"version":25,"maxContentLevel":34},"3c5a9b2b-ffc6-44d0-b94d-cff4a14dc7c8",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":68,"multiChoiceCorrect":70,"multiChoiceIncorrect":72,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},11,[69],"Aristotle defined life as the capacity for self-sustenance, growth, and decay. Why does fire challenge this definition?",[71],"Fire arguably also self-sustains, grows, and decays",[73,74,75],"Fire can reproduce and evolve, like living organisms","Fire does not grow or sustain itself over time","Fire cannot metabolize energy the way living organisms do",{"id":77,"data":78,"type":24,"maxContentLevel":34,"version":34,"reviews":81},"03a412e1-d59c-40f3-ba64-871233173a57",{"type":24,"markdownContent":79,"audioMediaId":80},"Part of the problem with definitions of life is that the organisms on Earth are almost impossibly diverse.\n\n![Graph](image://6edf9beb-c20e-42d9-a33e-23f5d5d134ed \"Diverse life forms. Compilation by Eryn Blaire, CC BY-SA 3.0 \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nLife ranges from single-celled organisms like bacteria to complex multicellular entities like humans and trees. These life forms exhibit a vast array of metabolic activities, reproductive strategies, and survival mechanisms.\n\nAny definition of life must be *broad* enough to include both bacteria and humans while being *specific* enough to exclude non-living matter.\n\nWe need to ask questions like ‘What do humans and bacteria have in common?’\n\n— But our answer cannot simply be something like ‘they are both on earth’ because that would also include rocks and refrigerators.","4bc1d264-232e-4e27-90c4-ecd06196ef08",[82],{"id":83,"data":84,"type":67,"version":34,"maxContentLevel":34},"eb386450-7d03-4b5b-9d22-bde58bbc83a5",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":85,"multiChoiceCorrect":87,"multiChoiceIncorrect":90,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[86],"Which of the below are key challenges in creating a definition of life?",[88,89],"Must be broad enough to capture both humans and bacteria","Must be specific enough to exclude non-living matter",[91,92],"Must be specific enough to exclude bacteria","Must be specific to life on Earth",{"id":94,"data":95,"type":24,"maxContentLevel":34,"version":34,"reviews":98},"eeb0e09f-1318-4e4c-82fe-998f42761702",{"type":24,"markdownContent":96,"audioMediaId":97},"The diversity of life is not the only problem.\n\nAnother challenge arises from edge cases in biology, such as viruses. Viruses display some characteristics of life, such as the ability to evolve, but lack others, like cellular structure and independent metabolic processes. \n\nViruses cannot reproduce on their own, relying instead on the **machinery of a host cell**. This has led to ongoing debates about whether viruses should be considered living.\n\n![Graph](image://728c27f4-d749-4f42-b9dd-64d1d9305977 \"A Herpes simplex virus. Image: Public domain, via Wikimedia Commons\")\n\nYet another difficulty is that the concept of life is also deeply dynamic. Living organisms evolve, adapt, and change over generations.\n\nThis evolutionary perspective suggests that any definition of life must encompass the very concept of change across time, accommodating both past and future forms of life.\n\nLife as it existed a billion years ago differs vastly from life today, and it will likely continue to evolve in ways we can't yet predict. Therefore, a comprehensive definition of life must be flexible enough to account for new life forms that may emerge in the future.","64413640-bebc-46f2-800c-c2d4dc607a8d",[99,110],{"id":100,"data":101,"type":67,"version":25,"maxContentLevel":34},"56eb87d6-dc1e-421b-9ef7-1c4fa0d5ecca",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":102,"multiChoiceCorrect":104,"multiChoiceIncorrect":106,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[103],"What is one characteristic of life that viruses lack?",[105],"Ability to reproduce independently",[107,108,109],"Ability to evolve over time","Ability to adapt to their environment","Ability to store genetic information",{"id":111,"data":112,"type":67,"version":24,"maxContentLevel":34},"3cd666e5-fcd7-4306-92e0-a7ab13cc6d8e",{"type":67,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":113,"binaryCorrect":115,"binaryIncorrect":117},[114],"What do viruses rely on for reproduction?",[116],"Host cell machinery",[118],"Independent metabolic processes",{"id":120,"data":121,"type":24,"maxContentLevel":34,"version":25},"3618ed12-09d0-4e38-8ccc-86173347d365",{"type":24,"markdownContent":122,"audioMediaId":123},"So how do we overcome these problems?\n\nFirstly, we can be more specific than Aristotle, because we now have a greater understanding of biological processes.\n\nFor example, instead of ‘self-sustenance and growth’, we can talk specifically about **metabolism**: the chemical processes that enable organisms to convert energy from their surroundings into forms they can use.\n\nAs well as ‘growth, and decay’ we can talk about **evolutionary adaptation**: an organism's ability to respond to changes in its environment, a key factor in the survival of species over time.\n\nWe now have a precise understanding of the different characteristics that are displayed by living organisms, including **cellular structure**, **reproduction**, **growth and development**, **metabolism**, and **adaptive evolution**.\n\nThis tile will track through each of these key characteristics, asking to what extent they help us to define life.","1344fb1a-74ac-4aaf-8535-07258c9a93bb",{"id":125,"data":126,"type":25,"version":128,"maxContentLevel":34,"summaryPage":129,"introPage":137,"pages":143},"8fbf9b30-3d4b-4721-9227-d11dbe0ee69e",{"type":25,"title":127},"Problem with Definitions of Life",6,{"id":130,"data":131,"type":34,"maxContentLevel":34,"version":25},"cf49059e-b762-43b7-9285-7d40c4fe21b1",{"type":34,"summary":132},[133,134,135,136],"Reproduction alone can't define life; crystals reproduce but aren't alive.","Metabolism definition fails; hurricanes use energy but aren't alive.","NASA's definition includes evolution; it's more comprehensive.","It is a broad combination of characteristics that must ultimately define life.",{"id":138,"data":139,"type":53,"maxContentLevel":34,"version":25},"2e0bcf6b-b1fc-4c58-8a8f-b6fb957b8ff9",{"type":53,"intro":140},[141,142],"How do crystals challenge the definition of life based on reproduction?","In what way does a hurricane mimic a living organism?",[144,183,199,229],{"id":145,"data":146,"type":24,"maxContentLevel":34,"version":25,"reviews":149},"61f8b3eb-3b2c-4df4-9a74-49f60c10479e",{"type":24,"markdownContent":147,"audioMediaId":148},"Our first orb drew attention to some of the problems with defining \"life\".\n\nThis orb will examine some of these definitions a little more closely. To what extent do they succeed at defining life (and if not: why not?)\n\nLet's start with one essential characteristic of life: **energy intake**.\n\nErwin Schrödinger described life as an **\"open system\" that stays organized by taking in energy and materials from its environment**.\n\nThis might sound a bit abstract, but essentially, he means that life resists breaking down over time, a process called **entropy**. Without a constant supply of energy, living things would fall apart and die. To avoid this, organisms take in energy from their surroundings to maintain their structure and function. \\\n\\\nFor example, plants use sunlight through photosynthesis to produce energy, grow, and stay organized. When a plant dies, it stops taking in energy, and entropy takes over, causing it to break down and decay.\n\nYet a definition based on energy intake has its limits.\n\nA hurricane also takes in energy, grows, and maintains structure. Yet, a hurricane is not *alive*. Why?\n\n![Graph](image://0585bb31-f6fd-438e-ae8a-c37e7879f062 \"Hurricane Katrina August 28 2005 NASA (Public domain), via Wikimedia Commons\")\n\nWell, hurricanes lack the intricate biochemical processes that consume energy in living organisms.\n\nWhen we talk about life needing energy, we are really referring to **metabolism**—the chemical reactions that power everything an organism does. To truly define life, we may want to specify certain *metabolic* processes — not just the intake of energy.","97deee42-21f3-4a93-a719-2f8e07bc1044",[150,162],{"id":151,"data":152,"type":67,"version":25,"maxContentLevel":34},"7b80c3cd-c9ef-4965-bca0-5af84f420802",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":153,"multiChoiceCorrect":155,"multiChoiceIncorrect":159,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[154],"Which of the following statements apply to metabolism?",[156,157,158],"Is an 'open system', taking in external energy sources","Resists natural tendency toward disorder (entropy)","Builds and maintains structure and function of organisms",[160,161],"Occurs mainly in plants","Is a 'closed system', fuelled without external energy sources",{"id":163,"data":164,"type":67,"version":25,"maxContentLevel":34},"a7d9a97f-4502-4b8b-85cd-ca1fc170a77f",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":165,"multiChoiceQuestion":169,"multiChoiceCorrect":171,"multiChoiceIncorrect":173,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":177,"matchPairsPairs":179},[166,167,168],"c775953c-9c40-4ce5-b03d-a4e9bd9111a3","dc60b074-63a3-45c2-935b-6cab53aeeb04","66080f81-fa22-41b7-b05f-a542c04720bb",[170],"Which of the below is an example of a metabolic process?",[172],"Photosynthesis",[174,175,176],"Reproduction","Homeostasis","Transpiration",[178],"Match the pairs below:",[180],{"left":181,"right":182,"direction":34},"Metabolism","Photosynthesis (in plants)",{"id":184,"data":185,"type":24,"maxContentLevel":34,"version":25,"reviews":188},"5584ebcd-623a-443a-9493-2ca01f118deb",{"type":24,"markdownContent":186,"audioMediaId":187},"Another pretty essential characteristic of life is **reproduction**.\\\n\\\nReproduction is a fundamental characteristic of all living things. It is the process by which living organisms produce new individuals, ensuring the continuation of their species.\n\nSome have attempted to *define* life by this ability to reproduce.\n\nThe biophysicist Edward Trifonov, for example, proposed that “life is self-reproduction with variations.” This idea suggests that life is defined by its ability to replicate itself while introducing small differences.\n\nLet's take bacteria: bacteria reproduce by dividing, often resulting in mutations that may provide advantages in changing environments.\n\nBut does this capacity really 'define' life?\n\n![Graph](image://4619d14a-3378-4a62-8ec6-2b7fbd5b4c6c \"Snowflake. Image by Adrian Tync (CC BY 4.0) \u003Chttps://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons\")\n\nNon-living entities, like crystals, can grow and exhibit variations during their formation. Crystals can even propagate by \"seeding\" new growth.\n\nYet, despite these similarities, crystals aren’t alive. Why?","8606fd98-b418-442f-9aaa-5cf8ea655cd6",[189],{"id":190,"data":191,"type":67,"version":24,"maxContentLevel":34},"111e8625-9bc5-46ac-9cb9-23a4e50ecae7",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":192,"multiChoiceCorrect":194,"multiChoiceIncorrect":196,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[193],"Why do crystals fit certain definitions of life?",[195],"They propagate by 'seeding' new growth",[197,198],"They have a metabolism","They pass on genetic information ",{"id":200,"data":201,"type":24,"maxContentLevel":34,"version":204,"reviews":205},"966313f5-16d1-4c22-88db-7f5b806f22f6",{"type":24,"markdownContent":202,"audioMediaId":203},"Crystals are not considered alive, despite their ability to grow and exhibit variation, because they lack the fundamental processes of **genetic inheritance and evolution.**\n\nSo, to be more specific in defining life, we could turn to the concept of **Darwinian evolution.**\n\n![Graph](image://72624703-1864-417c-bd78-db01e5380d29 \"The evolution of man. \u003Chttps://www.flickr.com/commons/usage/>, via Wikimedia Commons\")\n\nNASA defines life as “a self-sustaining chemical system capable of Darwinian evolution.” Here, “self-sustaining” means an organism can maintain balance and respond to its environment, while “chemical system” refers to metabolism.\n\nAs we’ll discuss more later, Darwinian evolution is different from Trifonov’s \"reproduction with variation.\" It shows how species change over time through natural selection. Traits such as size or behavior can help some individuals survive and reproduce better than others, allowing these traits to be inherited. Over time, this changes the species.\n\nThis is not the case with crystals.\n\nA broad definition of life should consider the ability of organisms to adapt and evolve across generations.","aa36a654-98ac-4f84-b5aa-d25080fda266",5,[206,214],{"id":207,"data":208,"type":67,"version":24,"maxContentLevel":34},"2460cb54-69c2-4ede-b665-a7fbb6bfe48d",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":209,"multiChoiceCorrect":211,"multiChoiceIncorrect":213,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[210],"What explains species change over time through natural selection?",[212],"Darwinian Evolution",[175,174,181],{"id":215,"data":216,"type":67,"version":34,"maxContentLevel":34},"d6b0f106-aa13-4db4-89f9-6dcbe84460e3",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":217,"matchPairsPairs":219,"matchPairsShowExamples":6},[218],"Match the pairs below",[220,223,226],{"left":221,"right":222,"direction":34},"Edward Trifonov","Proposed life is 'self-reproduction with variations'",{"left":224,"right":225,"direction":34},"Erwin Schrödinger","Described life as an 'open system' maintaining order by taking in low entropy material",{"left":227,"right":228,"direction":34},"NASA","Defines life as 'a self-sustaining chemical system capable of Darwinian evolution'",{"id":230,"data":231,"type":24,"maxContentLevel":34,"version":34,"reviews":234},"b4d5b01f-3282-4037-88e0-41b797e7517a",{"type":24,"markdownContent":232,"audioMediaId":233},"To conclude: definitions of life frequently come across problems and gaps.\n\nAs we've seen, hurricanes, fires, and crystals can mimic some life aspects. A hurricane extracts energy, grows, and eventually \"dies.\" A fire consumes fuel, spreads, and reacts to its environment. Crystals exhibit 'variation' during formation.\n\nEach characteristic—reproduction, metabolism, and response to stimuli—provides insight into life’s nature but is insufficient alone.\n\nEven specifying a capacity for 'Darwinian evolution' comes across problems. Under this definition, if NASA astronauts encountered a life-like entity on a distant planet without knowing its evolutionary history, could we say it was alive?\n\nIn the end, it's the combination of these characteristics that captures what it means to be alive.\n\nWe've touched on some of these already, but the next two tiles will examine these characteristics in greater detail:\\\n\\\n\n• Cellular structure\\\n• Growth and Development\\\n• Response to Stimuli\\\n• Metabolism\\\n• Homeostasis\\\n• Adaptation through Generations","8953bbe2-93d9-47a1-a598-692238e8d684",[235],{"id":236,"data":237,"type":67,"version":24,"maxContentLevel":34},"97771206-6ae0-46e7-bab9-3acd8e976098",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":238,"matchPairsPairs":239,"matchPairsShowExamples":6},[218],[240,243,246,249],{"left":241,"right":242,"direction":34},"Crystals","Grow and exhibit variations during formation",{"left":244,"right":245,"direction":34},"Hurricane","Draws in energy, 'grows', and maintains structure",{"left":247,"right":248,"direction":34},"Fire","Consumes fuel,  'grows', and reacts to environment",{"left":250,"right":251,"direction":34},"Bacteria","All of these",{"id":253,"data":254,"type":26,"maxContentLevel":34,"version":15,"orbs":257},"06ebe937-0105-4d82-a69b-87ee1a0f175d",{"type":26,"title":255,"tagline":256},"The Characteristics of Life (Part 1)"," How living things are built and grow over time",[258,426,589,734],{"id":259,"data":260,"type":25,"version":41,"maxContentLevel":34,"summaryPage":262,"introPage":270,"pages":276},"86b79139-b65a-478a-8f1d-c746cae7894e",{"type":25,"title":261},"Cellular Structure",{"id":263,"data":264,"type":34,"maxContentLevel":34,"version":24},"c8eeb19a-9b3c-4052-9660-46af347bed75",{"type":34,"summary":265},[266,267,268,269],"Cells are life's basic units, performing essential survival tasks.","Prokaryotic cells lack a nucleus; DNA floats in cytoplasm.","Eukaryotic cells have a nucleus; DNA is stored there.","Organelles like mitochondria power eukaryotic cells, boosting efficiency.",{"id":271,"data":272,"type":53,"maxContentLevel":34,"version":24},"43d94c71-bf11-4b1c-9866-6f2e7468fabe",{"type":53,"intro":273},[274,275],"What are the two main kinds of cell and the difference between them?","Why are mitochondria called the power plants of the cell?",[277,295,326,360,401],{"id":278,"data":279,"type":24,"maxContentLevel":34,"version":34,"reviews":282},"422778bb-885a-4d4e-ac74-fc6a691f914c",{"type":24,"markdownContent":280,"audioMediaId":281},"As we saw in the previous tile, defining 'What is life?' is best done by considering multiple core characteristics that living organisms share.\n\nThis tile introduces how organisms reproduce, grow, and develop—fundamental traits of all living things.\n\nBut to understand reproduction and growth, we first need to grasp the basic structure of all life: the cell.\n\n![Graph](image://f4e3145d-1a23-40a4-8cc9-4349d2c720cb \"General view of cells in the growing root-tip of the onion, via Wikimedia Commons\")\n\nAll life, large or small, is made up of cells, and all cells are capable of carrying out the functions necessary for life.\n\nWe’ll explore this further in our later tile on \"Cell Theory\", but for now, we're going to focus on **cell components.**\n\nThere are two main types of cells: **eukaryotic** and **prokaryotic**.\n\n**Eukaryotic** cells, found in plants, animals, and fungi, are complex, with a nucleus that stores genetic material, allowing them to control their genes more effectively. They also contain specialized parts (organelles), which we’ll cover in this orb.\n\n![Graph](image://7e12f650-791a-44bc-9985-f9e79eae77a7 \"Image: SadiesBurrow, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\n**Prokaryotic** cells, like those in bacteria, are simpler, lacking a nucleus. Their genetic material floats in a region called the nucleoid.\n\nDespite their simplicity, prokaryotic cells can thrive in extreme environments.","c99c502b-10ef-482c-a5a8-3b7b814a8137",[283],{"id":284,"data":285,"type":67,"version":25,"maxContentLevel":34},"794d27cf-6f85-4b31-b424-4dcdcea70078",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":286,"multiChoiceCorrect":288,"multiChoiceIncorrect":291,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[287],"Which of the following are characteristics of prokaryotic cells?",[289,290],"Found in bacteria and archaea","Lacks a defined nucleus",[292,293,294],"Contains a defined nucleus","Found in plants, animals, and fungi","Contain specialized parts (organelles)",{"id":296,"data":297,"type":24,"maxContentLevel":34,"version":41,"reviews":300},"cfef124f-df74-48db-a507-54e513b59b8e",{"type":24,"markdownContent":298,"audioMediaId":299},"To understand cell structure, let's think of a cell as a factory with different parts working together.\n\nThe outer perimeter of this factory is the **cell membrane**: a flexible barrier made mostly of lipids and proteins.\n\nThe membrane is **selectively permeable**, allowing essential materials to enter while keeping harmful elements out, like a gate that only lets in approved visitors and goods.\n\nIt also protects the cell and helps it communicate with its surroundings through receptors.\n\nInside the cell is the **cytoplasm**, a jelly-like substance (mostly water, with dissolved nutrients, salts, and proteins) that fills the space and surrounds all the cell’s parts.\n\nIt's like the factory floor: a workspace of the cell, which provides a medium in which other parts can operate and interact.\n\n![Graph](image://8763d9c0-9961-4b24-b33f-d87f8f966ec5 \"A simple animal cell (left) and a plant cell (right). Number 3 indicates the cell membrane; number 1 indicates the cytoplasm. Note that both cells have a nucleus (they are both 'Eukaryotic'). Image: domdomegg, CC BY 4.0 \u003Chttps://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons\")","2c4a43c2-dad1-434a-9f4d-eab86e779e9a",[301,313],{"id":302,"data":303,"type":67,"version":34,"maxContentLevel":34},"5d16c169-b6b3-4c73-8e6e-7208ed05764e",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":304,"multiChoiceCorrect":306,"multiChoiceIncorrect":310,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[305],"What is the function of the cell membrane?",[307,308,309],"Controls entry and exit of materials","Protection","Helps the cell communicate with its surroundings",[311,312],"Stores DNA","Captures sunlight for photosynthesis",{"id":314,"data":315,"type":67,"version":25,"maxContentLevel":34},"f04fab5b-c2e2-4398-942e-10bc3389dd07",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":316,"multiChoiceCorrect":318,"multiChoiceIncorrect":323,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[317],"Which of the following statements describe the cytoplasm?",[319,320,321,322],"Jelly-like substance","Composed mostly of water","Contains dissolved nutrients, salts, proteins","Medium for organelles to operate within a cell",[324,325],"Made of fat and proteins","Enclosed by nuclear envelope",{"id":327,"data":328,"type":24,"maxContentLevel":34,"version":25,"reviews":331},"b764cb18-b3ec-4492-a92a-fd7afb289b71",{"type":24,"markdownContent":329,"audioMediaId":330},"In both ​​prokaryotic and eukaryotic cells, you'll find **ribosomes** on the factory floor (in the cytoplasm). \\\n\\\n**Ribosomes** are like tiny assembly machines. They build proteins, following the instructions from the cell’s genetic material.\n\nIn prokaryotic cells (like bacteria), the genetic material and ribosomes float freely in the cytoplasm.\n\n![Graph](image://4eaa98f8-5633-44e9-a810-41ba939105a8 \"Prokaryotic and Eukaryotic Cells. SadiesBurrow, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nBut in eukaryotic cells (like plants and animals), things are more organized. To start with, the genetic material is stored in the **nucleus**.\n\nThe nucleus is a large sphere often located near the center of the cell, which functions like a secure central office. It stores the blueprints (DNA) for everything the factory produces, and sends out these instructions to different departments, ensuring everything runs smoothly.\\\n\\\nThe nucleus is enclosed by a double membrane called the **nuclear envelope**, which protects the DNA while allowing communication with the rest of the cell.\n\n![Graph](image://2e4c4207-2fe2-47b4-802e-10fe9c66201b \"A Nucleus. Image: Blausen.com staff (2014). \\\"Medical gallery of Blausen Medical 2014\\\". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436., CC BY 3.0 \u003Chttps://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons\")","050d347c-9606-4125-9eea-f83a234547db",[332,351],{"id":333,"data":334,"type":67,"version":24,"maxContentLevel":34},"b41bce7c-2dda-441b-80da-dcd35a566684",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":335,"multiChoiceQuestion":338,"multiChoiceCorrect":340,"multiChoiceIncorrect":342,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":346,"matchPairsPairs":347},[336,337],"14ccef0c-b96d-4498-9811-f8a3951a3bb0","7254f19e-b494-411b-b5d8-9d95e48c636c",[339],"What are ribosomes crucial for?",[341],"Protein synthesis",[343,344,345],"Storing DNA","Converting nutrients to ATP","Capturing sunlight for photosynthesis",[178],[348],{"left":349,"right":350,"direction":34},"Ribosomes","Crucial for protein synthesis",{"id":352,"data":353,"type":67,"version":25,"maxContentLevel":34},"7e44ef78-5627-4cec-8191-e825cefc2828",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":354,"multiChoiceCorrect":356,"multiChoiceIncorrect":359,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[355],"Which of the following statements describe the nucleus?",[357,311,325,358],"Large, spherical structure","Sends instructions to cell",[307,289],{"id":361,"data":362,"type":24,"maxContentLevel":34,"version":25,"reviews":365},"9e4e90fa-494a-4009-9fea-02163fafb444",{"type":24,"markdownContent":363,"audioMediaId":364},"Eukaryotic cells, unlike prokaryotic cells, also have other special parts, called **organelles**, that each do specific jobs. Organelles are like specialized departments in the factory, each handling a specific task.\n\n![Graph](image://80bfa7ba-9ca9-4a54-8334-c44a0b61c728 \"Organelles in an animal cell. Image: Majernik, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nOne of the most important of these organelles is the **mitochondria**.\n\nThe mitochondria are the power plants of the cell, converting nutrients into usable energy (ATP) through a process known as cellular respiration (—*we will come back to ATP in our section on metabolism*).\n\n**Mitochondria** are shaped like small capsules or beans and have an outer membrane and a highly folded inner membrane called cristae.\n\n![Graph](image://2e00b867-bed4-49f6-86f4-d9f4fe4439db \"Mitochondria with cristae. Image by Laboratoires Servier (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nThe **cristae** increase the **surface area** where energy production occurs, making the mitochondria highly efficient at generating the energy needed to fuel the cell's processes.","473e7053-8472-4533-9a45-cdf950c36bbe",[366,381],{"id":337,"data":367,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":368,"multiChoiceQuestion":369,"multiChoiceCorrect":371,"multiChoiceIncorrect":373,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":376,"matchPairsPairs":377},[333,336],[370],"What is the primary function of mitochondria?",[372],"Producing usable energy (ATP) through cellular respiration",[374,375,345],"Storing DNA in the nucleus","Controlling entry and exit of materials",[178],[378],{"left":379,"right":380,"direction":34},"Mitochondria","Produces usable energy (ATP) through cellular respiration",{"id":382,"data":383,"type":67,"version":24,"maxContentLevel":34},"62634d5f-07ee-4b01-98b9-02c51432efcc",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":384,"matchPairsPairs":386,"matchPairsShowExamples":6},[385],"Match the component of the cell with its analogy in a factory:",[387,390,393,395,398],{"left":388,"right":389,"direction":34},"Cell Membrane","Factory perimeter",{"left":391,"right":392,"direction":34},"Cytoplasm","Factory floor, where everything is located",{"left":349,"right":394,"direction":34},"Assembly machines",{"left":396,"right":397,"direction":34},"DNA","Blueprints",{"left":399,"right":400,"direction":34},"Nucleus","Central office",{"id":402,"data":403,"type":24,"maxContentLevel":34,"version":25,"reviews":406},"083e9a89-5c7d-40a3-aeed-59b0de6c23bb",{"type":24,"markdownContent":404,"audioMediaId":405},"The **endoplasmic reticulum** (ER) is another crucial part of the factory, with two different areas: the **rough ER**, which is covered in ribosomes and helps make and process proteins, and the **smooth ER**, which produces fats and helps detoxify the cell.\n\nIt's like having both an assembly line and a quality control department in the same factory.\n\n![Graph](image://a8cf0668-5c46-4ab4-a231-99b04889a647 \"A digram showing the endoplasmic reticulum and Golgi apparatus. Soumya730, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nOnce proteins and other materials are made, they move to the **Golgi apparatus**, which packages and sends them to their final destinations, much like a shipping department.\n\nSome cells, like those in plants, also have **chloroplasts**, which capture sunlight and turn it into chemical energy through photosynthesis—imagine them as solar panels powering the factory.\n\nAll these parts work together to keep the cell functioning smoothly.","ab7f4d01-ada6-4b77-8726-bc5bbb1e5ff5",[407],{"id":408,"data":409,"type":67,"version":25,"maxContentLevel":34},"239ccb70-ea3d-4986-bcd0-31d7518cf4bf",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":410,"matchPairsPairs":411,"matchPairsShowExamples":6},[178],[412,414,417,420,423],{"left":379,"right":413,"direction":34},"Site of cellular respiration, providing usable energy (ATP)",{"left":415,"right":416,"direction":34},"Rough Endoplasmic Reticulum (ER)","Covered in ribosomes, processes proteins",{"left":418,"right":419,"direction":34},"Smooth Endoplasmic Reticulum (ER)","Detoxifies cell, produces lipids",{"left":421,"right":422,"direction":34},"Golgi Apparatus","Shipping department of the cell (packages and sends proteins)",{"left":424,"right":425,"direction":34},"Chloroplasts","Solar panels of the cell (capture sunlight for photosynthesis)",{"id":427,"data":428,"type":25,"version":25,"maxContentLevel":34,"summaryPage":429,"introPage":437,"pages":443},"d9ed0cb6-e9a5-409c-ae46-39aaaf235713",{"type":25,"title":174},{"id":430,"data":431,"type":34,"maxContentLevel":34,"version":24},"49847c96-ec0d-4995-833b-5b47897e9dc5",{"type":34,"summary":432},[433,434,435,436],"Asexual reproduction creates identical offspring from one parent.","Binary fission is a quick asexual reproduction method in bacteria.","Sexual reproduction mixes genes from two parents for diversity.","Fertilization combines gametes to form a unique zygote.",{"id":438,"data":439,"type":53,"maxContentLevel":34,"version":24},"7c3e9399-cc35-4e25-b26d-5c51a9d03043",{"type":53,"intro":440},[441,442],"How does binary fission work in bacteria?","What makes sexual reproduction a game-changer for genetic diversity?",[444,486,525,555],{"id":445,"data":446,"type":24,"maxContentLevel":34,"version":25,"reviews":449},"4507656c-3601-401d-80c7-04d65dd6b0cf",{"type":24,"markdownContent":447,"audioMediaId":448},"Reproduction is a key trait of all living things, vital for life to continue across generations.\n\nAt the cellular level, reproduction is the **process by which cells create new cells**, ensuring that organisms grow, repair themselves, and survive through multiple generations.\n\nThere are two main types of reproduction: **asexual** and **sexual**.\n\n**Asexual reproduction** is simpler and faster. A single parent produces offspring that are genetically identical, or clones, of itself. This method is common in bacteria, some plants, fungi, and simple animals.\n\nThe advantage of asexual reproduction is efficiency, as it doesn’t require a mate, allowing rapid population growth in favorable conditions. However, since all offspring are identical, they share the same vulnerabilities to diseases or environmental changes.\n\n![Graph](image://47a2b42f-6f7e-4094-952f-117ce1ad8b87 \"Volvox algae, which undergoes asexual reproduction by Bwiltz (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nIn contrast, **sexual reproduction** involves two parents, resulting in genetically diverse offspring.\n\n![Graph](image://d41b18aa-6d90-4acb-b700-a4ee10e3ecbc \"White dog sleeping on the floor with genetically diverse puppies. Image: Basile Morin (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")","38f6dfda-0b61-4487-8a6e-384d8fbef51b",[450,461,479],{"id":451,"data":452,"type":67,"version":25,"maxContentLevel":34},"e5ec117a-d4f2-4b92-a0c9-d7fbe22eaae2",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":453,"multiChoiceCorrect":455,"multiChoiceIncorrect":459,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[454],"Which organisms can reproduce asexually?",[250,456,457,458],"Some plants","Some fungi","Some simple animals",[460],"Some mammals",{"id":462,"data":463,"type":67,"version":24,"maxContentLevel":34},"99f9ccf3-cee6-48d3-a3b4-d03a007a0d4f",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":464,"multiChoiceQuestion":468,"multiChoiceCorrect":470,"multiChoiceIncorrect":472,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":475,"matchPairsPairs":476},[465,466,467],"ca8dc0e3-ffae-46d0-a0cc-145330525d59","5cd48b81-86af-4a90-9ad4-8c2ce1c43cb6","78c37361-6cee-4b81-a3b0-fc3c3991ab71",[469],"What is asexual reproduction?",[471],"Single parent produces genetically identical offspring",[473,474],"Two parents produces genetically identical offspring","Single parent produces genetically diverse offspring",[178],[477],{"left":478,"right":471,"direction":34},"Asexual Reproduction",{"id":480,"data":481,"type":67,"version":25,"maxContentLevel":34},"45ebcd34-eecf-4b7f-84ed-24dcfeae2d38",{"type":67,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":482,"activeRecallAnswers":484},[483],"What is a negative consequence of asexual reproduction?",[485],"Offspring vulnerable to same environmental threats as the parent",{"id":487,"data":488,"type":24,"maxContentLevel":34,"version":25,"reviews":491},"45b777f0-3f9b-4459-aa92-55ecee4acd57",{"type":24,"markdownContent":489,"audioMediaId":490},"One of the simplest forms of **asexual** **reproduction** is binary fission, which is the primary method used by bacteria.\n\nIn **binary fission**, the cell duplicates its genetic material, ensuring that each new cell will have a complete copy of the DNA.\n\nAfter the cell duplicates its genetic material, it grows larger, and eventually, it splits into two identical daughter cells, each with its own copy of the DNA. This method allows bacterial populations to increase rapidly under favorable conditions.\n\n![Graph](image://6756957d-ab2c-4d51-9941-2a92f2450cec \"Binary fission (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")\n\nAnother example of **asexual reproduction** is budding, observed in organisms like Saccharomyces cerevisiae, a type of yeast.\n\nDuring **budding**, a small outgrowth, or bud, forms on the parent cell. The bud gradually enlarges and eventually detaches to become an independent cell, genetically identical to the parent.\n\n![Graph](image://50352fb5-1cb2-4f5a-8533-41c831060f39 \"S cerevisiae under DIC microscopy, displaying 'budding' in process. (Public domain), via Wikimedia Commons\")\n\nThis method is similar to binary fission but involves the formation of a distinct new cell from the original one.","453f27ec-5ee3-4de2-a8e8-5253fa393b01",[492,502,513],{"id":493,"data":494,"type":67,"version":24,"maxContentLevel":34},"22f1e78b-c7df-44b4-aa23-2c50aed2945d",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":495,"multiChoiceCorrect":497,"multiChoiceIncorrect":498,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[496],"Which organism commonly reproduces through binary fission?",[250],[499,500,501],"Plants","Fungi","Reptiles",{"id":503,"data":504,"type":67,"version":25,"maxContentLevel":34},"35035fed-41c9-4b62-83e3-ecef7cc767e4",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":505,"multiChoiceCorrect":507,"multiChoiceIncorrect":510,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[506],"What are the two steps involved in binary fission?",[508,509],"Step 1: Cell duplicates genetic material","Step 2: Cell grows larger and splits into two identical daughter cells",[511,512],"Step 1: Cell forms a bud","Step 2: Cell fuses with another cell",{"id":514,"data":515,"type":67,"version":24,"maxContentLevel":34},"5c8ec8ab-580c-4831-812a-adfb3dbd57ba",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":516,"multiChoiceCorrect":518,"multiChoiceIncorrect":521,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[517],"Which of the below applies to budding?",[519,520],"Small outgrowth forms on parent cell and becomes independent cell","Observed in Saccharomyces cerevisiae (yeast)",[522,523,524],"Involves fusion of gametes","Results in genetically diverse offspring","Occurs in bacteria",{"id":526,"data":527,"type":24,"maxContentLevel":34,"version":24,"reviews":530},"787e879a-a944-46da-b8bb-3a89ef3bf31e",{"type":24,"markdownContent":528,"audioMediaId":529},"**Sexual reproduction** differs from asexual reproduction because it involves two parents, and the offspring inherit a mix of genetic information from both.\n\nTo understand how this works, let's briefly talk about **chromosomes**. We’ll go into more detail in the \"Gene Theory\" section, but essentially, chromosomes are tiny packages of DNA (genetic material) inside almost every cell in your body. Together, these packages of DNA determine your traits, like eye color, height, and more—like pages in a manual that tells your body how to function.\n\nIn most of our cells, we have **two copies** of each chromosome—one from each parent.\n\nIn sexual reproduction, however, special cells called **gametes** are involved. In humans and other sexually reproducing organisms, there are two types of gametes:\n\n- **Sperm** (from the father)\n- **Egg** (from the mother)\n\n![Graph](image://21036d7b-8f60-4341-b506-ca9c1b2f1895 \"Abatus cordatus Female gamete (egg) and male gamete (sperm) (Public domain), via Wikimedia Commons\")\n\nEach **gamete** carries only **one copy** of each chromosome: half the usual number. For this reason, they're called **haploid cells** (haploid comes from the Greek word \"haploos,\" which means \"single\")**.**\\\n\\\nThe process that creates gametes is called **meiosis**, a type of cell division in which the number of chromosomes is reduced by half.","15e3f304-af57-4b7c-a631-897103f3199d",[531,543],{"id":532,"data":533,"type":67,"version":24,"maxContentLevel":34},"215fe1da-23c4-4f0c-aaa0-c21ca84b04a6",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":534,"multiChoiceCorrect":536,"multiChoiceIncorrect":540,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[535],"Which of the below apply to gametes?",[537,538,539],"Produced through meiosis","Two types: sperm (male) and egg (female)","Specialized sex cells",[541,542],"Formed by binary fission","Genetically identical to parent",{"id":544,"data":545,"type":67,"version":24,"maxContentLevel":34},"e69e94ac-058d-4551-92c9-19b0d9113104",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":546,"multiChoiceCorrect":548,"multiChoiceIncorrect":552,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[547],"Which of the below apply to meiosis?",[549,550,551],"Type of cell division","Reduces number of chromosomes by half","Produces gametes",[553,554],"Produces zygotes","Maintains whole set of chromosomes",{"id":556,"data":557,"type":24,"maxContentLevel":34,"version":24,"reviews":560},"e1a787a9-58c2-43fd-8ba9-f6f6a9206e5b",{"type":24,"markdownContent":558,"audioMediaId":559},"During fertilization, the male gamete (sperm) and the female gamete (egg) combine and form a new cell with a complete set of chromosomes: half from each parent.\n\nThis new type of cell, created from the fusion of two gametes, is called a **zygote**.\n\nSince the **zygote** contains a complete set of chromosomes (two sets: one from each parent) it's known as a **diploid cell**, from the Greek word \"diploos,\" meaning \"double\".\n\nDiploid cells contain the full genetic blueprint for the new organism.\n\n![Graph](image://b515ac8a-c06e-4573-bfe9-29a1a6a6bbb0 \"A 'haploid' sperm (top left) and a 'haploid' egg (top right), forming a 'diploid' zygote (bottom). Image: Quo-Fata FERUNT, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nUnlike asexual reproduction, where the offspring are clones of the parent, sexual reproduction shuffles the genetic deck, leading to offspring with different combinations of traits.\n\nThis genetic variation is crucial for the survival of populations, as it enables organisms to adapt to changing environments. For instance, in a population, genetic diversity can help ensure that some individuals are more resistant to a particular disease, allowing them to survive and reproduce.","ee28f305-94fb-44b7-9120-b112b3989b2e",[561,568,577],{"id":562,"data":563,"type":67,"version":24,"maxContentLevel":34},"af7a38d9-abaa-4bc3-ac3a-57018800ea77",{"type":67,"reviewType":41,"spacingBehaviour":24,"clozeQuestion":564,"clozeWords":566},[565],"During fertilization, the male gamete and the female gamete fuse to form a zygote. ",[567],"zygote",{"id":569,"data":570,"type":67,"version":24,"maxContentLevel":34},"5406f46f-9c62-4afe-889d-ea0970c8be4c",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":571,"multiChoiceCorrect":573,"multiChoiceIncorrect":575,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[572],"Which of the below statements apply to zygotes?",[574],"Contain a complete set of chromosomes (diploid)",[537,542,576],"Contain a half a set of chromosomes (haploid)",{"id":578,"data":579,"type":67,"version":24,"maxContentLevel":34},"a8e35cd3-a070-47c1-92d1-d5380eb5f93e",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":580,"multiChoiceCorrect":582,"multiChoiceIncorrect":585,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[581],"Why is the genetic diversity created by sexual reproduction important?",[583,584],"Enables organisms to resist diseases","Facilitates adaptation for changing environments",[586,587,588],"Leads to identical offspring","Reduces population growth","Increases vulnerability to diseases",{"id":590,"data":591,"type":25,"version":34,"maxContentLevel":34,"summaryPage":593,"introPage":601,"pages":607,"reviews":723},"d759992f-3e4d-41f6-b26c-6372deaf800a",{"type":25,"title":592},"Growth and Development",{"id":594,"data":595,"type":34,"maxContentLevel":34,"version":24},"d2d671dd-375d-49e6-b650-b164b8e8f89f",{"type":34,"summary":596},[597,598,599,600],"Growth involves cell size increase and division.","Mitosis creates identical cells for growth and repair.","Differentiation turns stem cells into specialized types.","Metamorphosis transforms organisms dramatically.",{"id":602,"data":603,"type":53,"maxContentLevel":34,"version":24},"471b3dcb-7a69-4ae8-9f2c-f38307931448",{"type":53,"intro":604},[605,606],"How do unicellular organisms like E. coli grow and reproduce?","What role does cell differentiation play in multicellular organisms?",[608,633,668,706],{"id":609,"data":610,"type":24,"maxContentLevel":34,"version":25,"reviews":613},"4504116a-3cb1-4ac3-ad5f-bb73ee5b9aa9",{"type":24,"markdownContent":611,"audioMediaId":612},"**Growth and development** are fundamental processes that characterize all living organisms, enabling them to survive, reproduce, and adapt in a continuously changing environment.\n\nAs we saw in the previous orb (**reproduction**), this process begins with a single cell, whether through the fusion of gametes in sexual reproduction or other means of asexual reproduction.\n\nIn **single-celled organisms** like bacteria, growth primarily involves increasing in size, followed by division. For example, the bacterium **Escherichia coli (E. coli)** grows from about 1–2 micrometers to 3–4 micrometers before dividing into two new cells through **binary fission**, a simple asexual reproduction process.\n\n![Graph](image://5dfab5d6-f11b-4536-9e4f-04ff8646662c \"Escherichia coli growth on agar by HansN. (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nUnder favorable conditions, E. coli can double in number every 20 minutes, leading to rapid population growth.\n\nFor **multicellular organisms**, growth and development are not just about increasing in size but involve complex, highly regulated processes that ensure organisms maintain their structural complexity and function.\\\n\\\nThis orb will examine these processes.","04e378ed-ae4b-4de8-9b66-58c048700730",[614],{"id":615,"data":616,"type":67,"version":24,"maxContentLevel":34},"a1cfd6c7-86c3-4b36-a040-139bc4d744c0",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":617,"multiChoiceQuestion":620,"multiChoiceCorrect":622,"multiChoiceIncorrect":624,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":628,"matchPairsPairs":630},[618,619],"ef53db23-c80c-45d4-9d3d-7dd274d46744","5ed585ac-adca-4228-91fe-ddf387fa0ff0",[621],"Which process involves E. coli splitting into two daughter cells?",[623],"Binary Fission",[625,626,627],"Mitosis","Cell Differentiation","Metamorphosis",[629],"Match the type of biological process to an example of that process in action:",[631],{"left":623,"right":632,"direction":34},"E. coli splitting into two daughter cells",{"id":634,"data":635,"type":24,"maxContentLevel":34,"version":25,"reviews":638},"ae51a6df-dea1-4612-be4e-d4930ac4df64",{"type":24,"markdownContent":636,"audioMediaId":637},"**Development** refers to the changes that occur as cells progress through their life cycle.\n\nIn **multicellular organisms**, development relies on **cell differentiation**, where unspecialized cells evolve into specialized cell types with distinct structures and functions.\n\n![Graph](image://b0dd8a75-920b-44aa-937f-aeea51150b84 \"Stem cell differentiation. Image: Haileyfournier, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nThis differentiation allows organisms to efficiently address environmental challenges and opportunities.\n\nFor instance, in humans and other multicellular organisms, cell differentiation results in the development of specialized systems such as the nervous system, muscles, and digestive system. These systems enable independent movement and the ability to process various foods for energy.\n\n**Stem cells** play a crucial role in this process, as they possess the unique ability to both replicate themselves and differentiate into specialized cells, such as muscle, nerve, or blood cells.\n\nThese processes are directed by an organism’s genetic code and influenced by environmental factors.","afbebdd3-d34b-4abb-b289-adeaaef3b54f",[639,654],{"id":465,"data":640,"type":67,"version":25,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":641,"multiChoiceQuestion":642,"multiChoiceCorrect":644,"multiChoiceIncorrect":646,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":650,"matchPairsPairs":651},[466,467,462],[643],"What of the below describes the process of cell differentiation?",[645],"Unspecialized cells developing into specialized cell types",[647,648,649],"Specialized cells dividing to increase in number","Unspecialized cells dramatically growing in size","Unspecialized cells undergo binary fission",[178],[652],{"left":626,"right":653,"direction":34},"Unspecialized cells develop into specialized cell types",{"id":166,"data":655,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":656,"multiChoiceQuestion":657,"multiChoiceCorrect":659,"multiChoiceIncorrect":661,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":664,"matchPairsPairs":665},[163,167,168],[658],"Which of the following is an example of cell differentiation?",[660],"Stem cells becoming muscle cells, nerves, blood cells, forming organs",[632,662,663],"A tree growing from a shoot into woody tissue","A caterpillar transforming into a butterfly",[178],[666],{"left":626,"right":667,"direction":34},"Stem cells becoming muscle, nerve, blood cells, organs",{"id":669,"data":670,"type":24,"maxContentLevel":34,"version":25,"reviews":673},"52fc0ec2-a9c1-42ed-a750-ca2013aea013",{"type":24,"markdownContent":671,"audioMediaId":672},"In **multicellular organisms**, growth occurs through an increase in the number of cells.\n\nWhile **prokaryotes** like bacteria commonly replicate via **binary fission**, a simpler process where the cell duplicates its DNA and splits, **eukaryotic cells** undergo a more complex division called **mitosis**.\n\nIn eukaryotes, cell growth is regulated by the **cell cycle**, which includes phases of growth, DNA replication, and division.\n\n**Mitosis** ensures that all necessary components, including DNA and organelles, are correctly divided between two new daughter cells.\n\n![Graph](image://8f52697d-820a-43ea-ac5a-5bb7a9de3c1b \"Unlike meiosis (which produced haploid gametes), mitosis produces two identical diploid daughter cells. Image by SadiesBurrow (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nUnlike binary fission, which occurs in cells without a nucleus (procaryotic cells) mitosis involves the division of the **nucleus**, followed by the rest of the cell, ensuring genetic consistency and functionality in multicellular organisms.\n\nMitosis plays a critical role in growth and tissue repair in multicellular organisms like plants and animals, where cells need constant replacement.\n\nSome unicellular **eukaryotes**, such as certain protists and fungi, also reproduce asexually using mitosis.","e1c4c543-bd68-40f9-aeb7-c4d1d8f441b9",[674,694],{"id":675,"data":676,"type":67,"version":25,"maxContentLevel":34},"0adbc440-b4c8-45d2-ae03-1f7a74834405",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":677,"multiChoiceQuestion":681,"multiChoiceCorrect":683,"multiChoiceIncorrect":685,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":689,"matchPairsPairs":690},[678,679,680],"fd5e32e5-a577-462e-8d8c-650a5d9d6806","90195c78-4794-4c3e-b18a-df2f97282f68","8dbf8af9-e84a-40d6-9018-647230c667de",[682],"What are the phases of the cell cycle?",[684],"Growth, DNA replication, division",[686,687,688],"Growth, differentiation, death","Replication, differentiation, death","Growth, replication, differentiation",[178],[691],{"left":692,"right":693,"direction":34},"Cell Cycle","Includes phases of growth, DNA replication, division",{"id":695,"data":696,"type":67,"version":24,"maxContentLevel":34},"a4c3ee45-c50a-4cda-af8e-f99314e6d0f9",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":697,"multiChoiceCorrect":699,"multiChoiceIncorrect":704,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[698],"Which of the below applies to mitosis?",[700,701,702,703],"Involves the division of a cell’s nucleus, followed by the rest of the cell","Results in two genetically identical daughter cells","Occurs for growth and development in multicellular organisms","Occurs for asexual reproduction in some eukaryotic fungi",[550,705],"Occurs for growth and development in prokaryotic cells",{"id":707,"data":708,"type":24,"maxContentLevel":34,"version":24,"reviews":711},"d08bc991-15cd-4d86-b839-eb6c758d755a",{"type":24,"markdownContent":709,"audioMediaId":710},"In some organisms, development involves dramatic transformations, such as **metamorphosis**. A well-known example is the transition of a caterpillar into a butterfly.\n\n![Graph](image://e2103ae1-ee5e-49ed-8faf-98084e3faa8b \"Metamorphosis of the Lappet moth (Public domain), via Wikimedia Commons\")\n\nDuring **metamorphosis**, the caterpillar undergoes significant cellular reorganization and differentiation. Its body plan, cell types, and functions change radically, allowing it to adapt to a new ecological role as a flying adult.\n\nMany plants also undergo profound developmental changes as they grow. For example, a tree's growth from a soft, green shoot into hard, woody tissue is a complex process involving cell division, elongation, and differentiation.\n\nIn young shoots, cells actively divide and elongate, allowing the plant to grow upward. As the tree matures, specialized cells differentiate into xylem, which provides structural support by forming the wood, and phloem, which helps transport nutrients.\n\nOver time, the outer layers develop into protective bark. These gradual changes enable the tree to stand tall, grow toward light, support its own weight, and adapt to various environmental conditions.","70f58398-7bd9-46f8-8422-b6ec52d79bdf",[712],{"id":713,"data":714,"type":67,"version":24,"maxContentLevel":34},"8057466c-fba2-4dcc-8602-3832c80cfbf8",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":715,"multiChoiceCorrect":717,"multiChoiceIncorrect":721,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[716],"Which of the following statements are true about metamorphosis?",[718,719,720],"Examples include caterpillar to butterfly transformation","Involves significant cellular reorganization and differentiation","Allows adaptation to new ecological roles",[722],"Can occur in unicellular organisms",[724],{"id":725,"data":726,"type":67,"version":24,"maxContentLevel":34},"5bf18767-4224-454a-ba28-c9a63785e939",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":727,"matchPairsPairs":728,"matchPairsShowExamples":6},[178],[729,732],{"left":730,"right":731,"direction":34},"Meiosis","Daughter cells produce gametes, with half the number of chromosomes each",{"left":625,"right":733,"direction":34},"Daughter cells are genetically identical, with full set of chromosomes",{"id":735,"data":736,"type":25,"version":41,"maxContentLevel":34,"summaryPage":738,"introPage":746,"pages":752},"1009d9ec-ac67-4f12-96c5-8d2a5a2dbc7a",{"type":25,"title":737},"Adaption through Generations",{"id":739,"data":740,"type":34,"maxContentLevel":34,"version":24},"df0d94ff-39be-4fb6-82c4-d3496c6db9fa",{"type":34,"summary":741},[742,743,744,745],"Adaptations evolve over generations, not instant responses.","Natural selection favors traits that boost survival.","Adaptations can be behavioral, physiological, or structural.","Adaptations involve trade-offs for survival advantages.",{"id":747,"data":748,"type":53,"maxContentLevel":34,"version":24},"8685ec0a-736a-41bf-93e5-7df76bdadcc9",{"type":53,"intro":749},[750,751],"What makes a trait an adaptation?","How does adaptation differ from a simple response to the environment?",[753,774,794],{"id":754,"data":755,"type":24,"maxContentLevel":34,"version":24,"reviews":758},"5152f06f-1032-4b2e-aa6a-c24525af8615",{"type":24,"markdownContent":756,"audioMediaId":757},"**Adaptation** is a fundamental concept in biology that explains how organisms evolve over generations to better survive and reproduce in their environments.\n\nThis process is driven by the natural selection of advantageous traits, which are characteristics that increase an organism's chances of survival and reproduction.\n\n![Graph](image://ac1f2469-0531-4fdc-ae3e-7bd7ebd03c9c \"A Giraffe, showcasing an adaptation to eating from tall trees. Image: Uganda Wildlife Educational Centre by Elisha Muwanguzi (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nThese traits can be **behavioral**, **physiological**, or **structural**, and they develop over many generations.\n\nBehavioral adaptations are actions organisms take to survive. For example, some birds migrate to warmer climates during winter to find food more easily and to avoid the harsh conditions of their usual habitats.\n\nThis behavior is not a conscious decision but rather an instinctual response that has evolved over generations because it increases the chances of survival and reproduction.","dfaaa347-90f2-4f5d-8a2b-ef64272dddb4",[759],{"id":680,"data":760,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":761,"multiChoiceQuestion":762,"multiChoiceCorrect":764,"multiChoiceIncorrect":766,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":770,"matchPairsPairs":771},[675,678,679],[763],"What of the following applies to the concept of 'adaptation' in biology?",[765],"Explains how organisms evolve to survive and reproduce",[767,768,769],"Describes how organisms migrate to new environments","Explains how organisms develop new species","Describes how organisms remain unchanged over time",[178],[772],{"left":773,"right":765,"direction":34},"Adaptation",{"id":775,"data":776,"type":24,"maxContentLevel":34,"version":25,"reviews":779},"7bc66c75-4002-4bde-b36c-2813a45c582d",{"type":24,"markdownContent":777,"audioMediaId":778},"**Physiological adaptations** involve changes in an organism's internal functions to cope with environmental challenges.\n\nFor instance, camels have adapted to their hot, arid desert environments by evolving the ability to go for long periods without water. This physiological adaptation allows them to survive in conditions that would be fatal to other animals.\n\n**Structural adaptations** are physical features of an organism that help it survive.\n\nThe thick fur of polar bears is a structural adaptation that provides insulation against the cold, enabling them to thrive in the Arctic environment. Similarly, ducks and other aquatic birds have **webbed feet**, which provide a larger surface area to push against water, making them better adapted for swimming in their aquatic environments.\n\n![Graph](image://44333297-614d-458c-8a22-e8ca18cc2819 \"Labuť, nohy (swan, feet) (Public domain), via Wikimedia Commons\")\n\nAdaptations are not always perfect. They represent compromises or trade-offs that enhance survival and reproduction in specific environments.\n\nFor example, the large body size of elephants helps them retain water and stay cool in hot climates but requires them to consume vast amounts of food daily. This trade-off is beneficial in environments where food is plentiful but could be detrimental in areas where food is scarce.","54c2f282-9ec2-4f8c-9fbe-7abab61c160e",[780],{"id":781,"data":782,"type":67,"version":24,"maxContentLevel":34},"ea5b6373-d677-493f-a583-ba260fc33ba9",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":783,"matchPairsPairs":784,"matchPairsShowExamples":6},[178],[785,788,791],{"left":786,"right":787,"direction":34},"Behavioral Adaptations","Birds migrating to warmer climates during winter",{"left":789,"right":790,"direction":34},"Physiological Adaptations","Camels evolving to go long periods without water",{"left":792,"right":793,"direction":34},"Structural Adaptations","Thick fur of polar bears for insulation",{"id":795,"data":796,"type":24,"maxContentLevel":34,"version":34,"reviews":799},"c34d24f9-42db-4e09-a042-83dc164ed421",{"type":24,"markdownContent":797,"audioMediaId":798},"Adaptations result from the **genetic variation** within a population.\n\nWhen environmental conditions change, certain variants of traits may provide some individuals with a survival advantage. These individuals are more likely to reproduce and pass on the advantageous traits to their offspring.\n\nOver time, the frequency of these traits increases in the population, leading to adaptation.\n\nThe process of adaptation through natural selection is slow and occurs over many generations. It is a continuous process because environments are constantly changing. As a result, organisms must continually adapt to survive. This dynamic interplay between organisms and their environments drives the diversity of life on Earth.\n\nIn summary, adaptation is a key mechanism by which life on Earth evolves in response to changing environments. These adaptations can be **behavioral**, **physiological**, or **structural**, and they are passed down through generations, leading to a diversity of life forms.","b9bb0135-d445-483a-9675-ed8d05308e74",[800],{"id":801,"data":802,"type":67,"version":34,"maxContentLevel":34},"9e2f6961-631b-4228-afd9-cb482088e9e7",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":803,"multiChoiceQuestion":806,"multiChoiceCorrect":808,"multiChoiceIncorrect":810,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":814,"matchPairsPairs":815},[804,805],"acc126f4-f4be-49fe-93e8-bf0bb1d63665","a5e10126-8afd-4725-beb2-29b0bc91d4b5",[807],"Which of the below best describes natural selection?",[809],"Slow process occurring over many generations",[811,812,813],"Rapid process occurring within a single generation","Instantaneous change in traits","Unrelated to environmental changes",[178],[816],{"left":817,"right":809,"direction":34},"Natural Selection",{"id":819,"data":820,"type":26,"maxContentLevel":34,"version":35,"orbs":823},"27cee849-67e7-4172-b2df-17c2c6bb8aeb",{"type":26,"title":821,"tagline":822},"The Characteristics of Life (Part 2)","How organisms stay alive and internally regulate",[824,971,1087],{"id":825,"data":826,"type":25,"version":34,"maxContentLevel":34,"summaryPage":827,"introPage":835,"pages":841},"956ff1dd-570a-4ace-af15-8143c6d9f157",{"type":25,"title":181},{"id":828,"data":829,"type":34,"maxContentLevel":34,"version":24},"68dc00fc-ff13-4042-a606-7387fe8f0241",{"type":34,"summary":830},[831,832,833,834],"Metabolism is all chemical reactions keeping organisms alive.","Anabolism builds complex molecules using energy from ATP.","Catabolism breaks down molecules, releasing energy as ATP.","Metabolism balances energy use and storage for life processes.",{"id":836,"data":837,"type":53,"maxContentLevel":34,"version":24},"73a8db81-21d6-40b5-84bf-4274881d39a9",{"type":53,"intro":838},[839,840],"How do cells 'spend' and 'save' energy in metabolism?","What role does ATP play in anabolism and catabolism?",[842,862,898,922],{"id":843,"data":844,"type":24,"maxContentLevel":34,"version":24,"reviews":847},"3763752c-7dce-4ad0-9833-5ff7770ba590",{"type":24,"markdownContent":845,"audioMediaId":846},"The previous tile looked at three important characteristics of life: cellular structure, reproduction, and growth and development. These processes concern how living things are built and grow over time.\n\nIn this tile, we’ll turn to the ways in which living things **stay alive** by using energy, constant internal regulation, and reacting to what’s happening around them: *metabolism*, *homeostasis*, and *response to stimuli*.\n\nFirst: **metabolism**.\n\nMetabolism refers to all the **chemical reactions** in living organisms that keep them alive.\n\nThese reactions allow organisms to grow, reproduce, repair damage, and respond to their environment.\n\nThe main purpose of metabolism is to convert the energy from food into a form that can be used to fuel cellular activities.\n\nAt the heart of metabolism are two key processes: **catabolism** and **anabolism**, which work together to manage how the body uses and stores energy.","41c12fa4-436d-4e5c-ad42-ad7ac74feda4",[848],{"id":678,"data":849,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":850,"multiChoiceQuestion":851,"multiChoiceCorrect":853,"multiChoiceIncorrect":855,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":859,"matchPairsPairs":860},[675,679,680],[852],"What is the definition of metabolism?",[854],"Sum of all chemical reactions in organisms",[856,857,858],"Breakdown of complex molecules","Synthesis of proteins","Conversion of light energy",[178],[861],{"left":181,"right":854,"direction":34},{"id":863,"data":864,"type":24,"maxContentLevel":34,"version":34,"reviews":867},"b8bf6b53-2cea-4f6d-b3ce-e02057d8ae15",{"type":24,"markdownContent":865,"audioMediaId":866},"**Catabolism** is the part of metabolism that breaks down complex molecules, like carbohydrates, lipids, and proteins, into simpler ones, which can be used for energy.\n\nFor example, when you eat food, your body's catabolic processes break it down into smaller components, such as glucose. Then, through processes like glycolysis and the citric acid cycle, glucose is further broken down, releasing energy.\n\nThis energy is stored in the form of **ATP** **(adenosine triphosphate)**, a molecule that cells use to fuel immediate activities—from exercising to essential bodily functions like keeping your heart beating and maintaining body temperature.\n\n![Graph](image://1ebff48d-3695-4552-97c0-fab32673dab9 \"Soldier running in water (Public domain), via Wikimedia Commons\")\n\nThink of **ATP** as the body's \"energy cash\" which it withdraws from a harder-to-access bank account. When the body needs energy, it withdraws the cash (**ATP**) through **catabolism**. Catabolism breaks down energy sources to produce ATP for immediate use.\n\nThe energy your body uses can come from two sources:\n\n1. Food you've just eaten\n2. Energy stored in your body, such as **glycogen** in your liver and muscles, or **fat** in your fat cells.\n\nThis is why you can continue exercising even when you haven’t just eaten—your body taps into stored energy, breaking it down to produce ATP, which powers your muscles to keep working.","cbd26d0c-f09a-4176-b27c-8c2969322bf3",[868,879],{"id":869,"data":870,"type":67,"version":34,"maxContentLevel":34},"1cf58c60-7ee3-4643-a6ef-968b9d303348",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":871,"multiChoiceCorrect":873,"multiChoiceIncorrect":876,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[872],"Which of the following apply to catabolic processes?",[874,875],"Breaks down carbohydrates, lipids, and proteins","Captures energy in the form of ATP",[877,878],"Synthesizes new proteins","Can capture light energy",{"id":880,"data":881,"type":67,"version":24,"maxContentLevel":34},"104b82bc-b5a6-43fa-a6d7-df3015e453be",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":882,"multiChoiceQuestion":886,"multiChoiceCorrect":888,"multiChoiceIncorrect":890,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":894,"matchPairsPairs":895},[883,884,885],"61138505-ef82-475e-82de-c0066edf0cc3","d52384d7-26fd-429a-b2b4-355c44826bad","767fe561-3a7c-4a61-8813-94037a8f686e",[887],"What happens to glucose in catabolic pathways?",[889],"Broken down in glycolysis and citric acid cycle",[891,892,893],"Synthesized into proteins","Stored as ATP","Captured as light energy",[178],[896],{"left":897,"right":889,"direction":34},"Glucose",{"id":899,"data":900,"type":24,"maxContentLevel":34,"version":24,"reviews":903},"4de39d7b-716d-4164-9cd6-5e699375f4c5",{"type":24,"markdownContent":901,"audioMediaId":902},"Once the body has obtained energy through catabolism, it can either use that energy for immediate needs or store it for later use through **anabolism**.\n\nAnabolism is the process of building complex molecules from simpler ones, using energy. These complex molecules are essential for growth, repair, and storage.\n\nFor example, after a workout, your body uses anabolism to repair and grow muscles by assembling proteins from amino acids.\n\n**Photosynthesis** is an anabolic process in plants, synthesizing sugar from carbon dioxide and water. This can then be stored as **starch** for future energy use or used to build other necessary molecules.\n\nAnabolic processes require energy, which comes from the **ATP** generated during catabolism.","7c29bf39-31a8-4735-b636-bfdfb9cafe9a",[904,913],{"id":905,"data":906,"type":67,"version":24,"maxContentLevel":34},"cf6f4c52-ba88-4925-8be2-93c01da2d36c",{"type":67,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":907,"binaryCorrect":909,"binaryIncorrect":911},[908],"What is the definition of anabolism?",[910],"Constructive part of metabolism (building complex molecules like proteins from simple ones, uses energy)",[912],"Deconstructive part of metabolism (breaking down complex molecules to release usable energy)",{"id":914,"data":915,"type":67,"version":24,"maxContentLevel":34},"9652a6e1-35df-4f25-b2d3-c16d5a7029ba",{"type":67,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":916,"binaryCorrect":918,"binaryIncorrect":920},[917],"Which process is an example of anabolism?",[919],"Photosynthesis synthesizes sugar from CO2 and water",[921],"Cellular respiration breaks down glucose into CO₂ and water",{"id":923,"data":924,"type":24,"maxContentLevel":34,"version":25,"reviews":927},"ec5bad75-e746-4422-b2ef-1de6d70e58ee",{"type":24,"markdownContent":925,"audioMediaId":926},"Metabolism is a balanced interplay of these anabolic and catabolic processes. It is a bit like managing a budget.\n\nIf **catabolism** is like withdrawing ready cash **(ATP)** from stores like food or body fat, then **anabolism** is the opposite—more like **depositing money into a savings account**. When your body builds larger molecules, such as glycogen (stored glucose) or fat, it’s storing energy for future use.\n\n![Graph](image://c44e0c38-3ec6-4871-8551-d9c29464bfa5 \"A diagram of the metabolism of food. Christinelmiller, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nThese \"savings\" can be accessed later when your body needs energy, like during long periods without food or intense physical activity. At that point, **catabolic processes** break down these stored molecules to release energy.\n\nWe will go into this in further depth later in our later tile on *homeostasis*, but it's worth noting that this balance between catabolism and anabolism is controlled by hormones such as **insulin** and **adrenaline**.\n\n**Insulin** helps the body store energy by promoting the uptake of glucose and the creation of glycogen, proteins, and fats. In contrast, hormones like glucagon and **adrenaline** trigger the breakdown of these stored molecules when the body needs energy.","1450d8f0-f48f-4f38-b13f-485a56f4147b",[928,940,959],{"id":929,"data":930,"type":67,"version":24,"maxContentLevel":34},"9229baff-7d0e-4162-86d1-7414aa0411d3",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":931,"multiChoiceCorrect":933,"multiChoiceIncorrect":937,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[932],"Which of the following statements about ATP are correct?",[934,935,936],"Acts as 'energy cash' for cells","Supplies energy for anabolic processes","Produced during catabolic reactions",[938,939],"Stored long-term in cells for future energy needs","Produced during anabolic reactions",{"id":941,"data":942,"type":67,"version":24,"maxContentLevel":34},"7eaf435d-ec13-4bfe-8a81-4c5ae58fd704",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":943,"multiChoiceQuestion":947,"multiChoiceCorrect":949,"multiChoiceIncorrect":951,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":955,"matchPairsPairs":956},[944,945,946],"d3fc9096-e2ab-4db1-8356-0839cbc4be46","ac27cf67-00ff-4a09-96d5-f986b635e5d5","4e48d196-2d73-464a-a6fa-70b9b74ace54",[948],"What is a function of the hormone 'adrenaline' in metabolism?",[950],"Stimulates catabolic processes",[952,953,954],"Stimulates anabolic processes","Synthesizes proteins","Captures light energy",[178],[957],{"left":958,"right":950,"direction":34},"Adrenaline",{"id":960,"data":961,"type":67,"version":25,"maxContentLevel":34},"9bbcf573-d9e6-48ae-bb89-3c7e9d566780",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":962,"multiChoiceCorrect":964,"multiChoiceIncorrect":967,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[963],"Which of the following are functions of the hormone 'insulin'?",[965,966],"Promotes glucose uptake","Stimulates anabolic processes (synthesis of glycogen, proteins, and fats)",[968,969,970],"Stimulates catabolic processes (breaking down carbohydrates and fats)","Releases energy from ATP","Captures light energy (through photosynthesis)",{"id":972,"data":973,"type":25,"version":41,"maxContentLevel":34,"summaryPage":974,"introPage":982,"pages":988},"abfb7528-d40a-4aaf-afd7-3fc2f4191397",{"type":25,"title":175},{"id":975,"data":976,"type":34,"maxContentLevel":34,"version":24},"1f0ef181-3b19-4141-b9e9-35f201ac2ebb",{"type":34,"summary":977},[978,979,980,981],"Homeostasis keeps internal conditions stable for survival, despite external conditions.","Feedback loops regulate things like body temperature and glucose levels.","Organisms use behavioral and physiological strategies for homeostasis.","Ecosystem stability relies on organism homeostasis.",{"id":983,"data":984,"type":53,"maxContentLevel":34,"version":24},"ab579beb-9103-4166-829b-f9b7a88b8ecc",{"type":53,"intro":985},[986,987],"Why is keeping a stable body temperature crucial for survival?","How do feedback loops help organisms stay balanced?",[989,1009,1046,1082],{"id":990,"data":991,"type":24,"maxContentLevel":34,"version":25,"reviews":994},"fa206d61-578a-4b8f-8212-7862f023663f",{"type":24,"markdownContent":992,"audioMediaId":993},"Homeostasis is a concept fundamental to the biology of all living organisms, referring to the **ability of an organism to maintain a stable internal environment** despite changes in external conditions.\n\nImagine a finely tuned thermostat in a house that adjusts the temperature to remain constant, regardless of the weather outside. Similarly, the human body maintains a steady internal temperature and regulates various processes, such as blood sugar levels and pH balance, ensuring that conditions within the body remain within a narrow, optimal range.\n\n![Graph](image://ac2515fc-8088-4a15-ba66-ca5a9d6daaf4 \"BC103 thermostat front view (CC0) \u003Chttp://creativecommons.org/publicdomain/zero/1.0/deed.en>, via Wikimedia Commons\")\n\nThis stability is essential for the survival and proper functioning of organisms. It ensures:\n\n- **Optimal Functioning of Enzymes and Cells**: Stable internal conditions allow enzymes and cell activity to function efficiently, supporting growth and development, energy production, and reproduction\n\n- **Coordination of Organ Systems**: In multicellular organisms, homeostasis enables different organ systems to work together effectively, maintaining overall health and balance.","1de2a1a7-7007-42bf-ad49-1775f6418867",[995],{"id":679,"data":996,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":997,"multiChoiceQuestion":998,"multiChoiceCorrect":1000,"multiChoiceIncorrect":1002,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1006,"matchPairsPairs":1007},[675,678,680],[999],"What is the definition of homeostasis?",[1001],"Ability to maintain a stable internal environment",[1003,1004,1005],"Ability to change internal environment","Ability to maintain a stable external environment","Ability to change external environment",[178],[1008],{"left":175,"right":1001,"direction":34},{"id":1010,"data":1011,"type":24,"maxContentLevel":34,"version":25,"reviews":1014},"45ff0b25-070d-4702-9f26-c2bfe8b0ed71",{"type":24,"markdownContent":1012,"audioMediaId":1013},"At its core, homeostasis involves the regulation of various physiological parameters within an organism.\n\nThese parameters can include **temperature**, **pH levels**, **glucose concentration**, and more.\n\nFor instance, humans maintain a body temperature of approximately 37°C, while the blood pH is tightly regulated close to 7.4.\n\nThese conditions are not random but are instead the result of evolution, tailored to the enzymes and cellular processes that drive life. If these internal conditions deviate too far from their ideal values, cellular processes can either slow down significantly or stop altogether, leading to illness or death.\n\nOrganisms have evolved a variety of mechanisms to maintain homeostasis, which include both **behavioral** and **physiological** strategies.\n\nFor example, when confronted with high ambient temperatures, humans can sweat to cool down through evaporative cooling, a physiological response.\n\nConversely, in colder environments, humans might shiver to generate heat or wear additional clothing, a behavioral response.\n\n![Graph](image://103f114f-ceed-46fd-baf2-1f4abffc210b \"A woman shivering in the cold. Image by Azlan DuPree (CC BY 2.0) \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")","8e059259-ac72-4e38-b710-3c655bf91eb9",[1015,1024,1035],{"id":1016,"data":1017,"type":67,"version":24,"maxContentLevel":34},"142c1c13-59d6-49e8-9606-cb620b28e42e",{"type":67,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1018,"activeRecallAnswers":1020},[1019],"Name 3 parameters that are regulated by homeostasis",[1021,1022,1023],"Temperature","pH levels","Glucose concentration",{"id":1025,"data":1026,"type":67,"version":24,"maxContentLevel":34},"f49d0db3-0ebb-440d-99a6-3b75829b6688",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1027,"multiChoiceCorrect":1029,"multiChoiceIncorrect":1031,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1028],"What is the approximate human body temperature?",[1030],"37°C",[1032,1033,1034],"36°C","38°C","39°C",{"id":1036,"data":1037,"type":67,"version":24,"maxContentLevel":34},"c638ca37-84ae-4a9f-8e8b-8b5fe99ffbdd",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1038,"multiChoiceCorrect":1040,"multiChoiceIncorrect":1042,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1039],"What is the tightly regulated blood pH level in humans?",[1041],"7.4",[1043,1044,1045],"7.0","7.2","7.6",{"id":1047,"data":1048,"type":24,"maxContentLevel":34,"version":41,"reviews":1051},"8d26e1d8-ee49-4ca1-8ec8-593336f5ac84",{"type":24,"markdownContent":1049,"audioMediaId":1050},"An organism's actions and reactions (to, for example, external temperature) are part of a feedback system that is the hallmark of homeostasis.\n\nThis **feedback system** is usually negative, meaning that the response to a change is to negate or reverse the change. For example, if an organism's body temperature rises, mechanisms are activated to decrease it, and vice versa.\n\n![Graph](image://a84edadc-1d16-4727-8196-a564c3a7191a \"Negative Feedback Loops. Image: OpenStax, CC BY 4.0 \u003Chttps://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons\")\n\nThe concept of feedback loops is central to understanding homeostasis.\n\nThese loops involve:\n\n1. (1) Sensors that monitor various conditions\n2. (2) Control centers that process this information\n3. (3) Effectors that produce responses to restore equilibrium.\n\nThe pancreas, for example, functions as both a **sensor** and a **control center** in glucose regulation by releasing insulin when blood glucose levels are high, prompting cells to absorb glucose and thus lowering blood glucose levels.\n\nThis is a complex mechanism and something we’ll be revisiting later in the pathway.","de9ee287-cb52-43b4-b1ca-c95d9a1cf062",[1052,1070],{"id":1053,"data":1054,"type":67,"version":34,"maxContentLevel":34},"499ff7ac-84c2-481d-9e07-93d8174b3f08",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1055,"multiChoiceQuestion":1058,"multiChoiceCorrect":1060,"multiChoiceIncorrect":1062,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1065,"matchPairsPairs":1066},[1056,1057],"913f437d-1d0b-4e6c-b821-60ac107981c2","ebcd182b-6147-4880-8b3e-c256c9c8324e",[1059],"Which concept is exemplified by the pancreas in glucose regulation?",[1061],"Feedback Loop",[1063,1064],"Thermoregulation","Osmoregulation",[178],[1067],{"left":1068,"right":1069,"direction":34},"Feedback Loops","The pancreas fulfilling its role in glucose regulation",{"id":1071,"data":1072,"type":67,"version":25,"maxContentLevel":34},"04ddbab1-aad5-446f-ac14-b59f8a9e76fc",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1073,"multiChoiceCorrect":1075,"multiChoiceIncorrect":1079,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[1074],"What roles does the pancreas play in glucose regulation?",[1076,1077,1078],"Functions as both a sensor and control center","Releases insulin when blood glucose levels are high","Releases glucagon when blood glucose levels are low",[1080,1081],"Regulates blood pressure","Produces digestive enzymes",{"id":1083,"data":1084,"type":24,"maxContentLevel":34,"version":25},"463dc474-d64e-4d38-ad65-ca8f9949eec3",{"type":24,"markdownContent":1085,"audioMediaId":1086},"Homeostasis is not just an individual concern but has implications for entire populations and **ecosystems**.\n\nThe stability of environmental conditions allows ecosystems to thrive and supports biodiversity.\n\n![Graph](image://da74654e-8440-4818-b173-2ec14cbba11b \"A freshwater crab in its natural environment. Image by Mendel264 (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nChanges in the external environment can disrupt the homeostasis of organisms within it, leading to ecological imbalances.\n\nThus, understanding homeostasis is not only crucial for biology but is also fundamental to ecology and environmental science.\n\nIn summary, homeostasis is a vital biological principle that ensures the stability of the internal environment of organisms, enabling life to flourish in a variety of conditions. Through a series of regulated feedback mechanisms, organisms can adjust to internal and external changes, promoting health, growth, and survival.","dac4ece4-a207-4c9e-a7b7-159dfd6b3bbf",{"id":1088,"data":1089,"type":25,"version":41,"maxContentLevel":34,"summaryPage":1091,"introPage":1099,"pages":1105},"4e0354b3-4099-4e32-9809-477f3cb24c0d",{"type":25,"title":1090},"Response to Stimuli",{"id":1092,"data":1093,"type":34,"maxContentLevel":34,"version":24},"abc91c8e-d274-4357-a1d4-e4b2e70f6603",{"type":34,"summary":1094},[1095,1096,1097,1098],"Organisms sense changes to survive and reproduce.","Bees use the sun for navigation and communication.","Migratory birds navigate using Earth's magnetic field.","Seasonal changes trigger immediate responses in animals and plants.",{"id":1100,"data":1101,"type":53,"maxContentLevel":34,"version":24},"0975738f-d448-4d12-9443-3081fa1e4377",{"type":53,"intro":1102},[1103,1104],"How do bees use the sun to find food?","What helps migratory birds navigate long distances?",[1106,1127,1132],{"id":1107,"data":1108,"type":24,"maxContentLevel":34,"version":41,"reviews":1111},"a5ca12bd-4ea3-46a0-967c-8db042ca8ff6",{"type":24,"markdownContent":1109,"audioMediaId":1110},"Organisms interact with their environment in a myriad of ways to ensure survival and reproduction. This interaction is a fundamental aspect of biology, encompassing both simple and complex organisms.\n\nThe ability to **respond to environmental stimuli** is crucial for navigating the challenges of life, such as finding food, seeking shelter, avoiding predators, and maintaining homeostasis.\n\n![Graph](image://20b5b5c0-0ba7-489f-9014-7ea880e2156e \"Sheep seek shelter from the approaching storm - geograph.org.uk - 2257068 by Alan Reid (CC BY-SA 2.0) \u003Chttps://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons\")\n\nAt the heart of these interactions is the concept of **environmental sensing**, where organisms detect immediate changes in their surroundings and respond in ways that enhance their chances of survival.\n\nThis process can be observed across the entire spectrum of life, from single-celled bacteria to complex multicellular organisms like humans.","50c1748d-38e9-44a4-933f-02f4af63f7f6",[1112],{"id":805,"data":1113,"type":67,"version":41,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1114,"multiChoiceQuestion":1115,"multiChoiceCorrect":1117,"multiChoiceIncorrect":1119,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1123,"matchPairsPairs":1124},[801,804],[1116],"What is the definition of Environmental Sensing?",[1118],"Detection of immediate changes in surroundings",[1120,1121,1122],"Tracking of long-term changes in surroundings","Detection of changes in internal environment","Detection of changes in genetic makeup",[178],[1125],{"left":1126,"right":1118,"direction":34},"Environmental Sensing",{"id":1128,"data":1129,"type":24,"maxContentLevel":34,"version":24},"75c5933b-e6b8-438b-bef0-86abb636bbbc",{"type":24,"markdownContent":1130,"audioMediaId":1131},"One example of an immediate response to the environment is seen in bees, which use the sun's position as a navigational aid.\n\nBees have a remarkable ability to **detect the angle of the sun** relative to their hive, even when it's partially obscured by clouds.\n\nThis allows them to communicate the direction and distance of food sources to other members of their colony through the \"**waggle dance**.\" The detection of the sun's position and the subsequent behavior is an immediate response to environmental stimuli that helps bees efficiently gather resources.\n\n![Graph](image://83eaaf16-3f65-40a5-b7be-b1cb9f55999c \"Bee waggle dance. Image: (Figure design: J. Tautz and M. Kleinhenz, Beegroup Würzburg.), CC BY 2.5 \u003Chttps://creativecommons.org/licenses/by/2.5>, via Wikimedia Commons\")\n\nSimilarly, many animals, including migratory birds and sea turtles, respond to Earth's magnetic field to navigate. These animals have **specialized sensory cells** that detect the magnetic field and help them orient themselves during long journeys.\n\nFor example, migratory birds use this magnetic sense to adjust their flight paths, ensuring they stay on course during migration. This response to the Earth's magnetic field is crucial for successful navigation over vast distances.\n\n![Graph](image://365408dc-93a6-439f-9f93-abf84933480e \"A Bar-tailed Godwit migration path (Public domain), via Wikimedia Commons\")","9a8514ac-00c3-4498-876a-09c8c03c6be7",{"id":1133,"data":1134,"type":24,"maxContentLevel":34,"version":25,"reviews":1137},"397cede7-29cc-41cf-b7da-0a46d3c7f48c",{"type":24,"markdownContent":1135,"audioMediaId":1136},"**Seasonal changes** also trigger immediate responses in many organisms.\n\nFor instance, some plants, like the common sunflower, exhibit a phenomenon known as **phototropism**, where they orient their leaves or flowers to track the sun’s movement across the sky.\n\nThis daily adjustment maximizes their exposure to sunlight, optimizing photosynthesis. While this response occurs daily, it's a direct reaction to the sun's position and is crucial for the plant's energy acquisition.\n\n![Graph](image://e0699078-984f-4f04-8825-409e400fa6f4 \"A house plant after having light from only one side by VolodyA! V Anarhist (FAL) \u003Chttp://artlibre.org/licence/lal/en>, via Wikimedia Commons\")\n\nIn animals, seasonal adaptations can also involve immediate behavioral changes. For example, as daylight hours shorten in the autumn, certain animals, like squirrels, respond by increasing their food-gathering activity to prepare for winter.\n\n![Graph](image://bbb110d2-5337-454d-8e31-d5157c2f2d63 \"Burying a nut (10458497135) by Peter Trimming (CC BY 2.0) \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")\n\nThis behavior is triggered by the change in day length and is a direct response to an environmental cue that helps the animal survive the upcoming colder months.\n\nIn summary, the timing and coordination of growth, reproduction, and homeostasis are strongly shaped by an organism's ability to sense and respond to environmental cues.\n\nAnd as we will return to later, this is also vital for evolutionary success: organisms that adapt effectively are more likely to survive, reproduce, and pass on their genes.","ca312787-ea15-4714-943d-f8419e1bc9d2",[1138],{"id":1139,"data":1140,"type":67,"version":25,"maxContentLevel":34},"530a082b-0c0c-4c6c-a521-7076d29316ad",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":1141,"matchPairsPairs":1142,"matchPairsShowExamples":6},[178],[1143,1146,1149,1152],{"left":1144,"right":1145,"direction":34},"Heliotropism","Plants track sun’s movement",{"left":1147,"right":1148,"direction":34},"Waggle Dance","Bees communicate food source direction and distance",{"left":1150,"right":1151,"direction":34},"Magnetic Sensing","Used by migratory birds and sea turtles",{"left":1153,"right":1154,"direction":34},"Seasonal Adaptations","Triggered by changes in day length",{"id":1156,"data":1157,"type":26,"maxContentLevel":34,"version":204,"orbs":1160},"0ffeec64-4db4-43b4-8baa-601ea154545f",{"type":26,"title":1158,"tagline":1159},"Cell Theory","The three principles that underly the importance of cells",[1161,1302,1359,1511],{"id":1162,"data":1163,"type":25,"version":34,"maxContentLevel":34,"summaryPage":1165,"introPage":1173,"pages":1179},"2f8a9c46-6ffa-4388-b829-f741bae04fd0",{"type":25,"title":1164},"The First Principle",{"id":1166,"data":1167,"type":34,"maxContentLevel":34,"version":24},"696662a0-ada4-4f1e-8a39-1914aac48da3",{"type":34,"summary":1168},[1169,1170,1171,1172],"All life forms are made of cells.","Robert Hooke discovered cells in cork in the 1600s.","Leeuwenhoek also saw living cells in pond water in the 1600s.","Schleiden and Schwann later confirmed all organisms have cells.",{"id":1174,"data":1175,"type":53,"maxContentLevel":34,"version":24},"3c22ce1d-6f91-4100-9fa3-40c887a8cb2c",{"type":53,"intro":1176},[1177,1178],"Who first discovered cells?","What did Anton van Leeuwenhoek see in pond water?",[1180,1203,1239,1268],{"id":1181,"data":1182,"type":24,"maxContentLevel":34,"version":24,"reviews":1185},"1878b95f-d542-4133-93d0-e1bce2440b1a",{"type":24,"markdownContent":1183,"audioMediaId":1184},"In the previous tiles, we explored the core characteristics of living organisms: reproduction, growth, metabolism (or the processing of energy), homeostasis, response to the environment, and adaptation through generations.\n\nWe saw that each of these characteristics helps to define life, though none of them alone provides a complete picture.\n\nBut it is important to understand that one of these unique characteristics is especially unique because it actually encompasses all the others at once: **the cellular makeup of organisms.**\n\nCell theory is the understanding that all known life on Earth is composed of and generated from cells.\n\nKey to cell theory are three core principles:\n\n**(1) All living organisms are composed of one or more cells.\\\n(2) The cell is the basic unit of structure and function in living organisms.\\\n(3) All cells arise from pre-existing cells.**\n\nWe are going to start here with the first principle: all living organisms are composed of one or more cells.\n\nSo how do we know this to be true?","39a53752-7aa9-4b05-9af0-834bdcabce64",[1186],{"id":1187,"data":1188,"type":67,"version":24,"maxContentLevel":34},"3eecb8cb-d2a1-4d87-b590-8a3e56c111e7",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":1189,"matchPairsPairs":1190,"matchPairsShowExamples":6},[178],[1191,1194,1197,1200],{"left":1192,"right":1193,"direction":34},"First principle of Cell Theory","All living organisms are composed of one or more cells",{"left":1195,"right":1196,"direction":34},"Second principle of Cell Theory","The cell is the basic unit of structure and function of life",{"left":1198,"right":1199,"direction":34},"Third principle of Cell Theory","All cells arise from pre-existing cells",{"left":1201,"right":1202,"direction":34},"Not a part of Cell Theory","All living organisms generate from non-living matter",{"id":1204,"data":1205,"type":24,"maxContentLevel":34,"version":34,"reviews":1208},"fb058e7f-f807-49cf-a267-8125e3c97e5f",{"type":24,"markdownContent":1206,"audioMediaId":1207},"To understand the first principle of cell theory (‘**all living organisms are composed of one or more cells**’), it’s worth winding back a few centuries.\n\nIn 1665, the world was on the cusp of a scientific revolution, with new tools and ideas beginning to reshape our understanding of the natural world. Chief among these tools was the microscope, with the power to reveal intricacies of nature previously invisible.\n\nIt was in this context that Robert Hooke, an experimenter for the Royal Society of London, made a discovery that would forever change the way we think about life.\n\n![Graph](image://9dd6c228-d80f-4f01-ae86-f9b5e23cc3d8 \"Hooke's Microscope and drawing of microscopic cork cells (Public domain), via Wikimedia Commons\")\n\nUsing a microscope that was rudimentary by today’s standards but revolutionary at the time, Hooke examined a thin slice of cork. As he adjusted the focus, he noticed something extraordinary: the cork was made up of tiny, box-like structures. These compartments reminded him of the small rooms, or \"cells,\" in a monastery, and so he named them \"cells.\"\n\nThough he didn’t know it at the time, Hooke had stumbled upon the basic building blocks of life, contained within a tiny sample of dead plant material.","ef130bfb-5463-4b2b-92f7-69e7a2a40d4f",[1209,1220],{"id":1210,"data":1211,"type":67,"version":25,"maxContentLevel":34},"41e94b66-2dae-4ed3-b403-c768fc5da79d",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1212,"multiChoiceCorrect":1214,"multiChoiceIncorrect":1216,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1213],"What did Robert Hooke discover when he observed cells under a microscope?",[1215],"He discovered dead plant cells in a slice of cork",[1217,1218,1219],"He observed living bacteria in a drop of pond water","He identified the movement of single-celled organisms","He found the structure of muscle fibers in living animals",{"id":1221,"data":1222,"type":67,"version":25,"maxContentLevel":34},"c3111b99-caf1-4928-b0fa-805e1f21d60f",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1223,"multiChoiceQuestion":1226,"multiChoiceCorrect":1228,"multiChoiceIncorrect":1230,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"orderAxisType":24,"orderQuestion":1234,"orderItems":1236},[1224,1225],"1e1a4fb4-862a-46ec-a102-e1a790f7ffc7","795564cc-955d-4f76-932a-0f5e13390eb1",[1227],"In what year did the London experimenter Robert Hooke observe room-like structures in cork?",[1229],"1665",[1231,1232,1233],"1674","1838","1859",[1235],"Put the following in order:",[1237],{"label":1238,"reveal":1229,"sortOrder":4},"Hooke observed room-like structures in cork, which he called 'cells'",{"id":1240,"data":1241,"type":24,"maxContentLevel":34,"version":25,"reviews":1244},"5d2f3e6b-38d8-428c-8ae7-9732b021f893",{"type":24,"markdownContent":1242,"audioMediaId":1243},"During the same period as Hooke’s experimenting, a Dutch scientist living in the Netherlands, Anton van Leeuwenhoek, was independently pushing the boundaries of microscopy.\n\nLeeuwenhoek was a curious and meticulous lens-maker who managed to create microscopes far more powerful than those used by Hooke.\n\nIn 1674, his craftsmanship paid off when he became the first person to observe living cells. He peered into a drop of pond water and saw it teeming with tiny, moving creatures.\n\nLeeuwenhoek called these organisms \"animalcules\"—little animals. Today, we know them as single-celled organisms, such as bacteria and protozoa.\n\n![Graph](image://2acc0184-cc64-4b9b-8bd6-05982462d1d3 \"Animalcules observed by anton van leeuwenhoek c1795 1228575 (Public domain), via Wikimedia Commons\")\n\nWhile Hooke had seen the signs of cellular life in dead plant matter, Leeuwenhoek observed cellular life in action.","c454101a-52a6-4480-a2e9-cf5988f3e70a",[1245,1257],{"id":1246,"data":1247,"type":67,"version":24,"maxContentLevel":34},"1dbc356f-8536-4360-933b-e27765ac179f",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1248,"multiChoiceCorrect":1250,"multiChoiceIncorrect":1253,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[1249],"Which of the following statements are true about Leeuwenhoek's 'Animalcules'?",[1251,1252],"Known today as single-celled organisms","Examples include bacteria and protozoa",[1254,1255,1256],"Known today as multi-celled organisms","Examples include fungi and algae","Known today as viruses",{"id":1224,"data":1258,"type":67,"version":25,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1259,"multiChoiceQuestion":1260,"multiChoiceCorrect":1262,"multiChoiceIncorrect":1263,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"orderAxisType":24,"orderQuestion":1264,"orderItems":1265},[1221,1225],[1261],"In what year did Leeuwenhoek observe living cells after improving microscope design?",[1231],[1229,1232,1233],[1235],[1266],{"label":1267,"reveal":1231,"sortOrder":24},"Leeuwenhoek observed living cells, after improving microscope design",{"id":1269,"data":1270,"type":24,"maxContentLevel":34,"version":25,"reviews":1273},"64865216-7427-45e7-ad66-84a96b89866f",{"type":24,"markdownContent":1271,"audioMediaId":1272},"Despite these early discoveries, it wasn't until the early 19th century that scientists began to piece together a more complete picture, as advances in microscope technology continued.\n\nIn 1838, a German botanist named Matthias Schleiden made a crucial observation: all plants, no matter how different they might seem, were composed of cells.\n\nShortly after, Theodor Schwann, a German zoologist, made a parallel discovery in the animal kingdom. He found that animals, too, were made up of cells.\n\n![Graph](image://7b0e3978-d837-4864-8bf9-d7fa19670f6a \"Dr. Th. Schwann's Cell structures under a microscope. (CC BY 4.0) \u003Chttps://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons\")\n\nSchwann and Schleiden's findings converged, leading to the proposal that all living organisms, whether plant or animal, are composed of cells.\n\nThis idea became known as cell theory, marking a pivotal moment in biology.","a3a20e98-22b2-41c9-a9ae-cd88387608ca",[1274,1285],{"id":1225,"data":1275,"type":67,"version":25,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1276,"multiChoiceQuestion":1277,"multiChoiceCorrect":1279,"multiChoiceIncorrect":1280,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"orderAxisType":24,"orderQuestion":1281,"orderItems":1282},[1221,1224],[1278],"In what year did Schleiden observe that all plants are composed of cells?",[1232],[1229,1231,1233],[1235],[1283],{"label":1284,"reveal":1232,"sortOrder":25},"Schleiden observed that all plants are composed of cells",{"id":1286,"data":1287,"type":67,"version":24,"maxContentLevel":34},"6004d5c6-4b03-4871-8641-69a2237d9f7e",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":1288,"matchPairsPairs":1289,"matchPairsShowExamples":6},[178],[1290,1293,1296,1299],{"left":1291,"right":1292,"direction":34},"Robert Hooke","Coined the word 'cells' after observing cork with a microscope",{"left":1294,"right":1295,"direction":34},"Anton van Leeuwenhoek","Dutch scientist, first to observe living cells, called organisms 'animalcules'",{"left":1297,"right":1298,"direction":34},"Matthias Schleiden","German botanist, observed all plants are composed of cells",{"left":1300,"right":1301,"direction":34},"Theodor Schwann","German zoologist, found animals are made up of cells",{"id":1303,"data":1304,"type":25,"version":25,"maxContentLevel":34,"summaryPage":1306,"introPage":1314,"pages":1320},"aba76a20-e378-48ed-ac78-b1590db364fd",{"type":25,"title":1305},"The Second Principle",{"id":1307,"data":1308,"type":34,"maxContentLevel":34,"version":24},"6a0b99af-2e88-414b-85b5-49bb9316fdc1",{"type":34,"summary":1309},[1310,1311,1312,1313],"Cells are life's basic functional units.","Organelles perform essential functions within cells.","Organelles can't function alone outside cells.","Life's complexity emerges at the cellular level.",{"id":1315,"data":1316,"type":53,"maxContentLevel":34,"version":24},"c54be6e8-dab6-4c54-a1d2-d05c6df4b901",{"type":53,"intro":1317},[1318,1319],"What do we mean by saying \"a cell the smallest unit of life\"?","How do organelles work together to keep a cell alive?",[1321,1337,1354],{"id":1322,"data":1323,"type":24,"maxContentLevel":34,"version":25,"reviews":1326},"8eeda8ab-3178-496b-bbd1-3f6c05749512",{"type":24,"markdownContent":1324,"audioMediaId":1325},"The realization that all living things, whether plants or animals, are made up of cells, arguably raised more questions than it answered.\n\nFor example, if all life is composed of cells, what exactly happens within these cells that makes them \"alive\"?\n\nHow do these tiny units carry out the complex processes required for life?\n\nThese questions brought scientists to the second principle of cell theory: **the cell is the basic unit of function in living organisms.**\n\nThis principle means that every activity that defines life—whether it’s respiration, digestion, growth, or reproduction—occurs within cells.","2ed235af-0ba3-42f8-af3f-c1d7f7b0a4f6",[1327],{"id":1328,"data":1329,"type":67,"version":24,"maxContentLevel":34},"7e283bfa-5a6b-497a-a187-e262a9bef3c9",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1330,"multiChoiceCorrect":1332,"multiChoiceIncorrect":1334,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1331],"What is the basic unit of structure and function in living organisms?",[1333],"Cell",[1335,399,379,1336],"Organelle","Molecule",{"id":1338,"data":1339,"type":24,"maxContentLevel":34,"version":25,"reviews":1342},"1938f77e-09b9-4004-a2c1-83cbdcf7ca51",{"type":24,"markdownContent":1340,"audioMediaId":1341},"This observation about cells — that they carry out, individually, all the processes of life, came from closer examination under a microscope.\n\nAs researchers like Schleiden and Schwann examined more and more cells, they began to notice that within each cell, there were even smaller components, each with a distinct role.\n\nThese components, later named **organelles**, seemed to be responsible for various essential functions.\n\nFor example, they discovered **mitochondria**, which act like tiny power plants, generating the energy a cell needs to carry out its activities. They also found the **nucleus**, which holds the cell's genetic material and controls its operations, much like a command center.\n\n![Graph](image://13bd0c66-6890-4631-a073-06a778673fc5 \"Mitochondria in a mammalian lung. Image: TEM (Public domain), via Wikimedia Commons\")\n\nHowever, an important realization emerged from these observations: none of these organelles could function on their own outside the cell.\n\nA mitochondrion, for instance, cannot produce energy by itself if isolated from the rest of the cell. The nucleus, on its own, cannot manage any cellular activities without the surrounding cellular machinery. It became clear that **it is only when all these organelles work together within the confines of a cell that life processes can occur.**","ce3ccc25-d53e-4bed-bac0-ce5e9b833a1a",[1343],{"id":1344,"data":1345,"type":67,"version":24,"maxContentLevel":34},"26a71b33-4fee-40e3-9a94-e30c0a25f14a",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1346,"multiChoiceCorrect":1348,"multiChoiceIncorrect":1351,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[1347],"Which of the following statements are true about organelles?",[1349,1350],"Smaller components within cells","Cannot function on their own outside the cell",[1352,1353],"Can function independently of the cell","Are the basic unit of function in living organisms",{"id":1355,"data":1356,"type":24,"maxContentLevel":34,"version":24},"336572d9-8c81-47fb-9f67-23af3c791bb2",{"type":24,"markdownContent":1357,"audioMediaId":1358},"This understanding of the cell as an irreducible unit of life is key.\n\nThe cell is not just the basic structural unit of life but also the smallest unit that can perform all the processes necessary for life.\n\nAnything smaller than a cell, such as an organelle or a molecule, might play a part in these processes, but it isn't alive on its own.\n\nLife, in its full complexity, emerges only at the level of the cell, where all these parts come together to function as a living entity.\n\nThis realization forms the second principle of cell theory, emphasizing the cell’s role not just as a building block, but as the fundamental unit of function in all living organisms.","49fd31a2-5380-4f23-a0a1-71b76773914e",{"id":1360,"data":1361,"type":25,"version":34,"maxContentLevel":34,"summaryPage":1363,"introPage":1371,"pages":1377},"756696cd-be58-48e4-be67-69924eaa3545",{"type":25,"title":1362},"The Third Principle",{"id":1364,"data":1365,"type":34,"maxContentLevel":34,"version":24},"9ea2ecca-f06d-42b8-bde8-b8dceee31273",{"type":34,"summary":1366},[1367,1368,1369,1370],"All cells come from pre-existing cells.","Spontaneous generation was disproven by Pasteur's experiment.","Pasteur's swan-neck flask showed life doesn't arise spontaneously.","Cell division explains life's continuity and growth.",{"id":1372,"data":1373,"type":53,"maxContentLevel":34,"version":24},"cdae8858-ea06-45fc-8788-de2fe20d776c",{"type":53,"intro":1374},[1375,1376],"How did Pasteur's experiment challenge spontaneous generation?","What does \"Omnis cellula e cellula\" mean?",[1378,1415,1420,1464],{"id":1379,"data":1380,"type":24,"maxContentLevel":34,"version":24,"reviews":1383},"4768d41d-3fb4-4403-917f-795e27258f0d",{"type":24,"markdownContent":1381,"audioMediaId":1382},"With the first two principles of cell theory established—that all living organisms are composed of cells, and that the cell is the basic unit of function in living organisms—one key question still remains.\n\nIf all cells are essential for life and all life is composed of cells, where do new cells come from? The answer to this question led to the third and final principle of cell theory, which we’ll explore next.\n\nThe third principle of cell theory states that all cells arise from pre-existing cells.\n\nIt may seem intuitive to us now, but for centuries, it was believed that life could spontaneously emerge from non-living matter.\n\nKnown as ‘spontaneous generation’, this was accepted as an explanation for how life could appear suddenly in environments where it hadn't existed before. Maggots seem to arise from nowhere from rotting meat; mold appears on walls.\n\n![Graph](image://d820a2bd-4b98-49d1-aa06-9a0c43d45bf7 \"Maggots on a decomposing animal (Public domain), via Wikimedia Commons\")\n\nHowever, as scientists developed a deeper understanding of cells through the second principle—which clarified that all vital functions occur within cells—it became increasingly clear that the idea of spontaneous generation was incompatible with what was known about life.","6963d9d3-2e4c-4562-abe9-b6f019227ef2",[1384,1400],{"id":466,"data":1385,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1386,"multiChoiceQuestion":1387,"multiChoiceCorrect":1389,"multiChoiceIncorrect":1391,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1395,"matchPairsPairs":1396},[465,467,462],[1388],"What is the definition of 'Spontaneous Generation'?",[1390],"Belief that life could emerge from non-living matter",[1392,1393,1394],"Process where one cell divides to form two new cells","Theory that life arises from pre-existing cells","Concept that life is created by divine intervention",[178],[1397],{"left":1398,"right":1399,"direction":34},"Spontaneous Generation","Theory that life could emerge from non-living matter",{"id":167,"data":1401,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1402,"multiChoiceQuestion":1403,"multiChoiceCorrect":1405,"multiChoiceIncorrect":1407,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1411,"matchPairsPairs":1412},[163,166,168],[1404],"Which of the following is an example of \"spontaneous generation\"?",[1406],"Maggots from rotting meat",[1408,1409,1410],"Bacteria from sterilized broth","Yeast from sugar solution","Plants growing from seeds",[178],[1413],{"left":1398,"right":1414,"direction":34},"Maggots from rotting meat, mold on walls.",{"id":1416,"data":1417,"type":24,"maxContentLevel":34,"version":24},"e11f0a43-9e07-464d-9f19-baa08e0da24b",{"type":24,"markdownContent":1418,"audioMediaId":1419},"So why is the second principle of cell theory incompatible with ‘**spontaneous generation**’?\n\nIf all the processes that define life, such as energy production, growth, and reproduction, occur inside cells, then it would be impossible for new life to just appear out of non-living material without first being organized into a cell.\n\nFor example, processes like metabolism, which involves converting nutrients into energy, or replication, where genetic material is duplicated, all require the coordinated action of organelles within a cell. These processes can't happen in a disorganized, non-living mass; they need the complex structure and environment provided by a cell.\n\nLife needs to be organized within a cell to function, so the idea that life could suddenly emerge from non-living matter didn't make sense.\n\n![Graph](image://110a09ec-65ed-4ea7-814f-6d77610bf90d \"Purple cells (Public domain), via Wikimedia Commons\")\n\nTo put it simply, if life is fundamentally cellular in nature—meaning that all life processes occur within cells—then new life cannot just \"appear\" without first being organized into these cellular structures.\n\nThe idea of **spontaneous generation**, which proposed that life could spontaneously emerge from non-living material, was at odds with this understanding. Life, as it is known and studied, requires a cellular framework to carry out the functions that define living organisms.","eb98383e-0ad5-4173-9fe9-10467821f1b2",{"id":1421,"data":1422,"type":24,"maxContentLevel":34,"version":34,"reviews":1425},"06b1945c-0125-4a34-a691-2ebd0d397489",{"type":24,"markdownContent":1423,"audioMediaId":1424},"The challenge to spontaneous generation reached its peak in the mid-19th century, with the work of Louis Pasteur.\n\nTo test whether spontaneous generation was possible, Pasteur used a special flask with a long, curved neck, known as a swan-neck flask. He filled the flask with a nutrient-rich broth and then boiled it to kill any existing microorganisms, ensuring that the broth was completely sterile.\n\nThe design of the flask was crucial: the long, curved neck allowed air to enter the flask but prevented dust particles and other contaminants, which might carry microorganisms, from reaching the broth.\n\nAfter boiling the broth, Pasteur left the flask exposed to the air. Because of the swan-neck shape, any airborne particles were trapped in the curves of the neck, and the broth remained clear, showing no signs of life, even after a long period.\n\n![Graph](image://579691d7-0f45-437f-b4df-aac332df17ec \"Experiment Pasteur English (Public domain), via Wikimedia Commons\")\n\nThis demonstrated that no life arose spontaneously in the broth despite its exposure to air. However, when Pasteur tilted the flask, allowing the trapped dust particles to mix with the broth, microorganisms quickly appeared, clouding the liquid. This showed that life came not from the air, but from microorganisms that were already present in the environment.","876ff1e5-818e-4d9c-b881-8b9b0fcf489d",[1426,1444,1455],{"id":1427,"data":1428,"type":67,"version":25,"maxContentLevel":34},"891dab6c-9fb5-4202-bcc7-e23c4b1a60b0",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1429,"multiChoiceQuestion":1432,"multiChoiceCorrect":1434,"multiChoiceIncorrect":1436,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1440,"matchPairsPairs":1441},[1430,1431],"9dd48e65-bf2a-4aa4-83bf-ba256c112765","54009495-5229-4a39-9706-68cd7abc0c9d",[1433],"Who challenged the concept of spontaneous generation in the mid-19th century?",[1435],"Louis Pasteur",[1437,1438,1439],"Rudolf Virchow","Robert Koch","Alexander Fleming",[178],[1442],{"left":1435,"right":1443,"direction":34},"Demonstrated that life did not arise spontaneously in sterile broth.",{"id":1445,"data":1446,"type":67,"version":24,"maxContentLevel":34},"1d57d7c1-3e25-4fe1-9082-c06fa5ebf859",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1447,"multiChoiceCorrect":1449,"multiChoiceIncorrect":1451,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1448],"What was the consequence of Pasteur's experiment?",[1450],"Demonstrated that life did not arise spontaneously in sterile broth",[1452,1453,1454],"Proved that life could arise from non-living matter","Showed that air is necessary for life","Demonstrated that life arises from chemical reactions",{"id":1456,"data":1457,"type":67,"version":25,"maxContentLevel":34},"8f92618d-b9ae-4806-ad43-09b0d8ac90b9",{"type":67,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":1458,"binaryCorrect":1460,"binaryIncorrect":1462},[1459],"Why was the curved swan-neck flask used by Pasteur?",[1461],"The neck curves allowed in air but blocked contaminants",[1463],"The neck curves blocked all air from entering the whole flask",{"id":1465,"data":1466,"type":24,"maxContentLevel":34,"version":25,"reviews":1469},"1a8e5b3b-bf28-43d1-ab05-69264b84ee2f",{"type":24,"markdownContent":1467,"audioMediaId":1468},"Pasteur’s experiment was crucial to the acceptance of the third principle of cell theory: all cells arise from pre-existing cells.\n\nThis principle not only refuted the outdated concept of spontaneous generation but also provided a scientific foundation for understanding the perpetuation of life at the cellular level.\n\nIt explained how life continues through the process of cell division, where one cell divides to form two new cells, core to the mechanisms behind growth, development, and reproduction.\n\nIt reinforced the importance of cells as the basic units of life, emphasizing that life is an unbroken chain of cellular division and inheritance from one generation to the next.\n\nRudolf Virchow, a German physician and pathologist, formalized this principle in 1855 with his famous phrase \"**Omnis cellula e cellula**,\" meaning \"Every cell from a cell.\"\n\nTogether with the first two principles, this third tenet completes cell theory, which remains a cornerstone of modern biology.","e8a8d18d-2831-4122-badf-39daeb7871c2",[1470,1485,1500],{"id":1430,"data":1471,"type":67,"version":25,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1472,"multiChoiceQuestion":1473,"multiChoiceCorrect":1475,"multiChoiceIncorrect":1477,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1481,"matchPairsPairs":1482},[1427,1431],[1474],"What principle of cell theory did Rudolf Virchow formalise using a Latin phrase? ",[1476],"Omnis cellula e cellula' (Every cell from a cell)",[1478,1479,1480],"Cellula generat vitam' (The cell generates life)","'Omnis cellula e nucleum' (Every cell from a nucleus)","'Omnis organismum ex cellula' (Every organism from a cell)",[178],[1483],{"left":1437,"right":1484,"direction":34},"Formalized the principle 'Omnis cellula e cellula' (Every cell from a cell)",{"id":467,"data":1486,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1487,"multiChoiceQuestion":1488,"multiChoiceCorrect":1490,"multiChoiceIncorrect":1491,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1495,"matchPairsPairs":1496},[465,466,462],[1489],"What is the definition of 'Cell Division'?",[1392],[1492,1493,1494],"Process where cells merge to form a single cell","Theory that cells arise from non-living matter","Concept that cells are the basic unit of life",[178],[1497],{"left":1498,"right":1499,"direction":34},"Cell Division","Process where one cell divides to form two new cells.",{"id":1501,"data":1502,"type":67,"version":24,"maxContentLevel":34},"8bc7811e-72fa-49b1-940f-b3c3f8c5fcc2",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1503,"multiChoiceCorrect":1505,"multiChoiceIncorrect":1507,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1504],"In what year did Rudolf Virchow formalize the third principle of cell theory?",[1506],"1855",[1508,1509,1510],"1845","1865","1875",{"id":1512,"data":1513,"type":25,"version":25,"maxContentLevel":34,"summaryPage":1515,"introPage":1523,"pages":1529},"d702b6a2-c460-48d3-ba0c-2afa201f4cbd",{"type":25,"title":1514},"Illustrating the Second Principle",{"id":1516,"data":1517,"type":34,"maxContentLevel":34,"version":24},"4529a3e3-6980-4b6a-aa33-3431fc27243a",{"type":34,"summary":1518},[1519,1520,1521,1522],"Cells perform all life functions, like growth and reproduction.","E. coli divides by binary fission, doubling its size first.","Euglena uses an eyespot to move toward light for photosynthesis.","Bacteria adapt through mutations, leading to antibiotic resistance.",{"id":1524,"data":1525,"type":53,"maxContentLevel":34,"version":24},"130e7b14-a8c5-40bf-b05c-93d0081c285a",{"type":53,"intro":1526},[1527,1528],"How does E. coli demonstrate the cell's role in reproduction?","What role does Euglena's eyespot play in its survival?",[1530,1551,1556,1598],{"id":1531,"data":1532,"type":24,"maxContentLevel":34,"version":24,"reviews":1535},"6511782a-b4db-41d8-895f-a011d79f0cd2",{"type":24,"markdownContent":1533,"audioMediaId":1534},"In earlier chapters, we've explored the characteristics that define life: reproduction, growth, metabolism, homeostasis, response to the environment, and adaptation through generations.\n\nWell, according to the **second principle of cell theory** (the cell is the basic unit of function in living organisms), we know that cells must *themselves* be capable of performing **all** these functions that we observe in living organisms.\n\nFor example, in our section on reproduction, we saw how in organisms that reproduce sexually, gametes cells undergo meiosis.\n\nLet’s also consider a prokaryotic cell like Escherichia coli (E. coli). In binary fission, the bacterial cell replicates its DNA, enlarges, and then splits into two identical daughter cells.\n\nAnd just like whole organisms must **grow and develop** before they are ready to reproduce (think about the process of reaching sexual maturity in mammals), cells themselves must also undergo processes of growth and development through a series of stages that prepare the cell for reproduction.\n\nAgain, let's take E. coli:\n\nDuring its growth phase, an E. coli cell can increase in size from about 1-2 micrometers to around 3-4 micrometers before it is ready to divide.\n\nThis growth is accompanied by an increase in cellular components, such as ribosomes and membrane material. The cell must accumulate enough resources in order to successfully divide.","cb325b3f-9af5-4c3a-986e-36d77b1ea634",[1536],{"id":618,"data":1537,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1538,"multiChoiceQuestion":1539,"multiChoiceCorrect":1541,"multiChoiceIncorrect":1543,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1547,"matchPairsPairs":1548},[619,615],[1540],"What is an example of asexual reproduction in cells?",[1542],"E. coli replicates DNA and splits in binary fission",[1544,1545,1546],"Gametes undergoing meiosis","Euglena moving toward light","Bacteria entering dormancy",[629],[1549],{"left":1550,"right":1544,"direction":34},"Sexual Reproduction",{"id":1552,"data":1553,"type":24,"maxContentLevel":34,"version":25},"7b670f59-8612-4e92-9c42-b7cf39809c02",{"type":24,"markdownContent":1554,"audioMediaId":1555},"Metabolism—the chemical processes that convert nutrients into energy—is another vital function that occurs on the level of the cell.\n\nEukaryotic cells generate and control energy through cellular respiration. As we have already seen, during cellular respiration, mitochondria convert glucose and oxygen into ATP (adenosine triphosphate), the energy cash used by the cell to power all its activities, from synthesizing proteins to dividing.\n\nSimilarly, while **homeostasis** occurs on the level of entire organisms, involving complex interactions between the brain and external stimulus, homeostasis *also* occurs in individual cells, through cellular mechanisms that ensure a stable internal environment.\n\nThe cell membrane’s selective permeability can regulate what enters and exits the cell. For example, cells must control the concentrations of ions and molecules inside and outside their membranes to maintain proper function.\n\n![Graph](image://32769cc2-9510-44b5-9689-d53af45dc129 \"Diagram of ions moving through the cell membrane. Image: Д.Ильин: vectorization, CC0, via Wikimedia Commons\")\n\nA striking example of cellular metabolic control and homeostasis is found in certain bacteria that can enter a state of dormancy, where they reduce their metabolic activity in order to survive extreme conditions.\n\nFor example, Russell Vreeland and his team revived a bacterium that had been present for 250 million years inside a salt crystal.\n\nDuring dormancy, the bacteria's metabolism was nearly at a standstill, allowing it to survive in a hostile environment. When conditions became favorable, the bacterium resumed normal metabolic activity, demonstrating the cell’s ability to manage energy and maintain homeostasis over vast timescales.","d95efdaf-9e2b-4a79-9cd0-beafe5c052a1",{"id":1557,"data":1558,"type":24,"maxContentLevel":34,"version":25,"reviews":1561},"91b3503d-043c-4866-a2e0-65901b079527",{"type":24,"markdownContent":1559,"audioMediaId":1560},"Cells, like whole organisms, must be able to sense and respond to their environment to survive. This responsiveness is crucial for adapting to changing conditions and ensuring survival.\n\nAn excellent example of cellular response is seen in Euglena, a unicellular organism that has a specialized structure called an eyespot.\n\n![Graph](image://6e375ad7-0faf-4688-b1ad-858e97dc9832 \"Euglena Viridis (CC0) \u003Chttp://creativecommons.org/publicdomain/zero/1.0/deed.en>, via Wikimedia Commons\")\n\nThe eyespot detects light, allowing Euglena to move toward it through a process called phototaxis. By moving toward light, Euglena optimizes its ability to perform photosynthesis in its chloroplasts, converting light into the energy needed for survival.\n\nConversely, if the light is too intense, Euglena can move away to avoid damage, showing how cells can dynamically adjust their behavior based on environmental cues.\n\nThis ability to respond to stimuli is not unique to Euglena. All cells have ways of detecting and reacting to environmental changes. For example, bacterial cells have receptors on their membranes that can sense the presence of nutrients or toxins.\n\nWhen these receptors detect a favorable or harmful substance, they trigger a response, such as moving toward a food source or away from a toxic chemical, ensuring the cell’s survival in diverse conditions.","3f8350f3-c8dc-4c89-8a6a-698e9e1bc81d",[1562,1572,1588],{"id":1563,"data":1564,"type":67,"version":24,"maxContentLevel":34},"b54b42ef-0928-4d30-a40e-0b7a4c57e94f",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1565,"multiChoiceCorrect":1567,"multiChoiceIncorrect":1570,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[1566],"Which of the following are examples of cellular responses to stimuli?",[1568,1569],"Bacteria enter dormancy under stressful conditions","Euglena moving away from intense light",[1544,1571],"Development of antibiotic resistance in E. coli",{"id":168,"data":1573,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1574,"multiChoiceQuestion":1575,"multiChoiceCorrect":1577,"multiChoiceIncorrect":1579,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1583,"matchPairsPairs":1584},[163,166,167],[1576],"How does Euglena respond to the very intense light?",[1578],"Moves away from it to avoid damage",[1580,1581,1582],"Enters dormancy","Replicates DNA and splits","Develops antibiotic resistance",[178],[1585],{"left":1586,"right":1587,"direction":34},"Cellular Response to stimuli","Euglena moves away from intense light (phototaxis) to avoid damage ",{"id":1589,"data":1590,"type":67,"version":24,"maxContentLevel":34},"acab2c52-4b75-4e7d-a6ea-16e558453560",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1591,"multiChoiceCorrect":1593,"multiChoiceIncorrect":1595,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1592],"What is the term for movement toward or away from light in organisms?",[1594],"Phototaxis",[730,1596,1597],"Binary fission","Dormancy",{"id":1599,"data":1600,"type":24,"maxContentLevel":34,"version":25,"reviews":1603},"42e0a9f4-39d2-4a9a-aaa6-715f4afd1450",{"type":24,"markdownContent":1601,"audioMediaId":1602},"**Adaptation through generations**, a cornerstone of evolution, also occurs at the cellular level. Cells pass on genetic information during reproduction, and sometimes mutations—changes in the DNA—occur. These mutations can confer new traits that enhance survival, leading to adaptation over time.\n\nA well-documented example of cellular adaptation is the development of antibiotic resistance in bacteria like E. coli.\n\nWhen exposed to antibiotics, most bacterial cells may die, but a few with a random mutation that confers resistance can survive. These resistant cells then reproduce, passing on the resistance trait to their offspring.\n\nOver several generations, the population shifts toward antibiotic resistance, making the once-effective drug less useful. This process demonstrates how cells can adapt through mutations and natural selection, allowing them to survive in changing environments.\n\n![Graph](image://fbbc2d6d-b767-4cec-98dc-0dca2e0c276f \"Antibiotic sensitivity and resistance. Image: by Dr Graham Beards (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nIn summary, the fundamental processes that define life—reproduction, growth, metabolism, homeostasis, response to stimuli, and adaptation—are all present and active within individual cells. These processes reflect the second principle of cell theory, emphasizing that the cell is the basic unit of function in all living organisms.","7c3020f4-75f7-433e-9b50-f863360be801",[1604],{"id":619,"data":1605,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1606,"multiChoiceQuestion":1607,"multiChoiceCorrect":1609,"multiChoiceIncorrect":1610,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1614,"matchPairsPairs":1615},[618,615],[1608],"What is an example of cellular adaptation in bacteria?",[1571],[1611,1612,1613],"Movement toward light","Entering dormancy","Undergoing meiosis",[629],[1616],{"left":1617,"right":1618,"direction":34},"Cellular Adaptation","Antibiotic resistance in bacteria like E. coli",{"id":1620,"data":1621,"type":26,"maxContentLevel":34,"version":41,"orbs":1624},"1caa0c32-186e-42df-b298-9df71cd80ffa",{"type":26,"title":1622,"tagline":1623},"Chemistry of Life","The chemical building blocks of organisms",[1625,1760,1934,2081,2222,2361],{"id":1626,"data":1627,"type":25,"version":25,"maxContentLevel":34,"summaryPage":1629,"introPage":1637,"pages":1643},"46e88a40-dd68-4cc7-9f9c-93cfad8e49ea",{"type":25,"title":1628},"The Role of Carbon",{"id":1630,"data":1631,"type":34,"maxContentLevel":34,"version":24},"f5db6966-0f8c-438b-b66b-718804d2842d",{"type":34,"summary":1632},[1633,1634,1635,1636],"Carbon forms stable bonds with many elements, including itself.","Carbon's four bonds enable complex, life-essential molecules.","Carbohydrates showcase carbon's role in energy and structure.","Carbon's versatility is what drives the diversity of life on Earth.",{"id":1638,"data":1639,"type":53,"maxContentLevel":34,"version":24},"2cb8e1a3-5067-47de-9f69-d0b978f1081c",{"type":53,"intro":1640},[1641,1642],"Why is carbon called the backbone of life?","How do carbon's bonds create molecular diversity?",[1644,1661,1698,1725],{"id":1645,"data":1646,"type":24,"maxContentLevel":34,"version":24,"reviews":1649},"99e4dd4f-4fe8-4f31-a2cb-337960db7be0",{"type":24,"markdownContent":1647,"audioMediaId":1648},"All life on Earth is composed of chemicals arranged in specific structures. While the periodic table includes many elements, only a particular subset—like carbon, hydrogen, oxygen, and nitrogen—plays a central role in the chemistry of life, forming stable and complex molecules that are essential for biological processes.\n\nThis tile will track through the chemical compositions that make up living organisms, starting with perhaps the most important of all: **carbon**.\n\n![Graph](image://e6cfe26e-c0ba-4299-b113-a72a11f23a2b \"Graphene. Image by AlexanderAlUS (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nThe image above is a graphical representation of a kind of structure known as **graphene**, an extraordinary material made of a single layer of carbon atoms. The carbon atoms are arranged in a hexagonal lattice, resembling a honeycomb.\n\nDespite being only one atom thick, graphene is incredibly strong, lightweight, and highly conductive, and these days it is being used in cutting-edge technologies, such as nanoscale machines, ultra-sensitive sensors, and advanced electronic devices.\n\nBut long before these technologies, nature used the unique properties of **carbon** to build life.","1dabfafa-31cc-4606-907a-ccdeb8787c66",[1650],{"id":1651,"data":1652,"type":67,"version":24,"maxContentLevel":34},"dc42fe6c-8760-4a9d-a613-2233fa8b1146",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1653,"multiChoiceCorrect":1655,"multiChoiceIncorrect":1657,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1654],"What is the structure of graphene?",[1656],"Single layer of carbon atoms, arranged in a hexagonal lattice",[1658,1659,1660],"Multiple layers of carbon atoms, arranged in a cubic lattice","Single layer of carbon atoms, arranged in a triangular lattice","Multiple layers of carbon atoms, arranged in a hexagonal lattice",{"id":1662,"data":1663,"type":24,"maxContentLevel":34,"version":25,"reviews":1666},"8187c65b-2d69-43c5-b5e3-dcc847c490fc",{"type":24,"markdownContent":1664,"audioMediaId":1665},"Carbon is a fundamental element in the chemistry of life, acting as the backbone for a wide variety of biological molecules.\n\n![Graph](image://b5c00ee2-9660-407a-b681-9d447fe8a8aa \"Pure Carbon by Texas Lane (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nThis is because carbon has a unique ability to **form stable bonds** with many other elements, including with itself. This characteristic allows for the creation of complex molecules essential for life, such as **proteins**, **nucleic acids**, **carbohydrates**, and **lipids**.\n\nSpecifically, carbon atoms can form **four covalent bonds** with other atoms. This means that a single carbon atom can connect with up to four other atoms, creating a three-dimensional structure.\n\nFor example, in a methane molecule (**CH4**), carbon forms four bonds with hydrogen atoms, which gives the molecule a stable structure.\n\n![Graph](image://682cefc4-866c-4e4b-93d8-eac6b4cbb229 \"Methane (CH4). Image: DynaBlast, CC BY-SA 2.5 \u003Chttps://creativecommons.org/licenses/by-sa/2.5>, via Wikimedia Commons\")\n\nThis ability to form multiple bonds makes carbon incredibly versatile, allowing it to be the foundation for large and complex molecules, known as macromolecules.","ad7a2d95-91d3-44db-8203-66e186aea998",[1667,1678],{"id":1668,"data":1669,"type":67,"version":25,"maxContentLevel":34},"7824db47-4f0d-43ef-8df8-a0fc28edd468",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1670,"multiChoiceCorrect":1672,"multiChoiceIncorrect":1674,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1671],"What is a key characteristic of carbon that allows for the creation of complex molecules essential for life?",[1673],"Forms stable bonds with many elements",[1675,1676,1677],"Forms unstable bonds with many elements","Forms stable bonds with only a few elements","Cannot form bonds with other elements",{"id":1679,"data":1680,"type":67,"version":24,"maxContentLevel":34},"6502c142-3cda-412d-8934-504f7a029002",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1681,"multiChoiceQuestion":1685,"multiChoiceCorrect":1687,"multiChoiceIncorrect":1689,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1693,"matchPairsPairs":1694},[1682,1683,1684],"a5bd75d3-d96e-4e37-978b-239b5ea75f94","5bbc4aa2-2f8b-48b7-8173-f7e32890eb79","82ee88fe-76ee-418c-ac47-f64c23ce3968",[1686],"How many covalent bonds can a single carbon atom form?",[1688],"Four",[1690,1691,1692],"Two","Three","Five",[178],[1695],{"left":1696,"right":1697,"direction":34},"Carbon","Can form four covalent bonds",{"id":1699,"data":1700,"type":24,"maxContentLevel":34,"version":24,"reviews":1703},"d315d97d-143c-4cd6-b1a9-b7b8f7f6bcbc",{"type":24,"markdownContent":1701,"audioMediaId":1702},"Carbon's ability to form double and triple bonds with other carbon atoms adds another layer of diversity to molecules. These types of bonds change the shape and properties of the molecules. For example, double bonds make a molecule more rigid and less flexible, affecting how it behaves and reacts with other substances.\n\nIn addition to bonding with other carbon atoms, carbon can also form stable bonds with elements like **oxygen**, **nitrogen**, **sulfur**, and **phosphorus**.\n\nWhen carbon bonds with these elements, it creates **functional groups**, which are specific clusters of atoms that give a molecule certain properties and make it behave in a predictable way.\n\nFunctional groups are important because they determine how a molecule interacts in chemical reactions. For example:\n\n- The **hydroxyl group** (–OH) makes a molecule more likely to dissolve in water.\n- The **carboxyl group** (–COOH) makes a molecule acidic, like in fatty acids.\n\nThese functional groups are essential for processes in living organisms, such as metabolism, gene expression, and cell communication.","e0c92515-834f-45d4-b05f-1445c0a34267",[1704,1711],{"id":1705,"data":1706,"type":67,"version":24,"maxContentLevel":34},"59838fb0-8063-40a4-8283-2e2347a913ce",{"type":67,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1707,"activeRecallAnswers":1709},[1708],"What are 'functional groups'?",[1710],"Groups of atoms bonded to carbon that give molecules specific chemical properties (e.g. acidity or interaction with water)",{"id":1712,"data":1713,"type":67,"version":24,"maxContentLevel":34},"9719e4db-b9e0-4914-8892-5c8e799dff43",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1714,"multiChoiceCorrect":1716,"multiChoiceIncorrect":1721,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[1715],"What elements are common in the creation of functional groups?",[1717,1718,1719,1720],"Oxygen","Nitrogen","Phosphorus","Sulfur",[1722,1723,1724],"Helium","Neon","Lead",{"id":1726,"data":1727,"type":24,"maxContentLevel":34,"version":24,"reviews":1730},"0733fcce-90c5-4326-9029-6c038a83b0ab",{"type":24,"markdownContent":1728,"audioMediaId":1729},"**Carbohydrates** are a prime example of the complexity and diversity that carbon can create in biological systems.\n\n![Graph](image://8799a3cf-65d4-4572-ba2d-a5210fb4132e \"The chemical composition of glucose (a corbohydrate) made of carbon (C), oxygen (O) and hydrogen (H). Image: Ben; Yikrazuul, Public domain, via Wikimedia Commons\")\n\nCarbohydrates are composed of **carbon**, **hydrogen**, and **oxygen**, and they play crucial roles in energy storage, structural integrity, and cellular communication in living organisms.\n\n**Simple carbohydrates**, like glucose, serve as a primary energy source for cells.\n\nWhen multiple glucose molecules bond together, they can form **complex carbohydrates**, such as **starch** and **cellulose**, which are essential for energy storage in plants and structural support in plant cell walls, respectively.\n\nHumans and other animals consume **starchy plants**, like **potatoes**, to access this stored energy, breaking down the starch into glucose for use in metabolic processes.\n\n![Graph](image://09526bc1-e406-46b1-a7ea-a0b332d8443b \"Potato and cross section (GFDL 1.2) \u003Chttp://www.gnu.org/licenses/old-licenses/fdl-1.2.html>, via Wikimedia Commons\")","6394d1c1-e7cf-40aa-b36b-0f1d53c90d2a",[1731,1744],{"id":1732,"data":1733,"type":67,"version":24,"maxContentLevel":34},"be1baf8b-6ee3-4561-8a51-eef3871cfebe",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1734,"multiChoiceCorrect":1736,"multiChoiceIncorrect":1740,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[1735],"Which statements apply to cellulose?",[1737,1738,1739],"Formed by multiple glucose molecules","Provides structural support in plant cell walls","Complex carbohydrate",[1741,1742,1743],"Primary energy source for cells","Essential for energy storage in plants","Simple carbohydrate",{"id":1745,"data":1746,"type":67,"version":24,"maxContentLevel":34},"b66948d6-c9c8-429b-8d5b-e652fb802791",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1747,"multiChoiceQuestion":1751,"multiChoiceCorrect":1753,"multiChoiceIncorrect":1754,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1757,"matchPairsPairs":1758},[1748,1749,1750],"ae30301a-a7e9-41d7-9cf0-329cf273ee2b","a663a8c4-c303-4864-a6fb-031af06e5850","e116e165-e5aa-467b-aa03-5723877b6de0",[1752],"Which simple carbohydrate is the primary source of stored chemical energy for cells?",[897],[1755,1756],"Starch","Cellulose",[178],[1759],{"left":897,"right":1741,"direction":34},{"id":1761,"data":1762,"type":25,"version":24,"maxContentLevel":34,"summaryPage":1764,"introPage":1773,"pages":1779},"4f1a3325-355e-471c-b19e-1561f779d913",{"type":25,"title":1763},"Proteins",{"id":1765,"data":1766,"type":34,"maxContentLevel":34,"version":24},"07d186e0-23d0-4819-818e-01b7a30d2188",{"type":34,"summary":1767},[1768,1769,1770,1771,1772],"Proteins are chains of amino acids determining shape and function.","Enzymes are proteins that speed up essential chemical reactions.","Structural proteins like collagen and keratin provide cell support.","Antibodies are proteins that protect the body from infections.","Proteins transport substances and facilitate cell signaling",{"id":1774,"data":1775,"type":53,"maxContentLevel":34,"version":24},"b4ff04d3-a56c-4ea0-b64f-e2d5a65764c0",{"type":53,"intro":1776},[1777,1778],"What are proteins made of?","How do enzymes speed up reactions?",[1780,1835,1881,1902],{"id":1781,"data":1782,"type":24,"maxContentLevel":34,"version":24,"reviews":1785},"f011e2d6-7b5a-4fce-b4b0-748854ed7320",{"type":24,"markdownContent":1783,"audioMediaId":1784},"Proteins are essential molecules that play a crucial role in the characteristics of life. They are made up of smaller units called amino acids, which are linked together in long chains.\n\n![Graph](image://68d85488-06f0-4c92-8c50-c6985bf46ee3 \"A long protein chain (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nThe **sequence** of these amino acids determines the protein's shape and function.\n\nProteins are involved in almost every process within living organisms, making them vital for life.\n\nOne of the primary roles of proteins is to act as enzymes. **Enzymes** are proteins that speed up chemical reactions in the body, which is essential for metabolism. Without enzymes, reactions would occur too slowly to sustain life.\n\nFor example, digestive enzymes help break down food into nutrients that the body can use for energy, growth, and repair.","d2c72ae7-f3f6-49f6-a6dd-ff47b384ef94",[1786,1803,1819],{"id":1787,"data":1788,"type":67,"version":24,"maxContentLevel":34},"a3966c62-685e-42e2-956e-979e5c38e234",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1789,"multiChoiceQuestion":1792,"multiChoiceCorrect":1793,"multiChoiceIncorrect":1795,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1799,"matchPairsPairs":1800},[1790,1791],"0547cb2c-eaa9-45f3-a2ba-67b3348ba0ff","023f7e19-c1b4-49d1-8b77-2f35113274e8",[1777],[1794],"Amino acids in long chains",[1796,1797,1798],"Fatty acids in long chains","Nucleotides in short chains","Carbon in a lattice",[178],[1801],{"left":1763,"right":1802,"direction":34},"Made of amino acids in long chains",{"id":944,"data":1804,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1805,"multiChoiceQuestion":1806,"multiChoiceCorrect":1808,"multiChoiceIncorrect":1810,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1814,"matchPairsPairs":1815},[941,945,946],[1807],"What are enzymes?",[1809],"Proteins that speed up chemical reactions",[1811,1812,1813],"Proteins that provide structural support","Proteins that transport substances","Proteins that transmit messages into the cell",[178],[1816],{"left":1817,"right":1818,"direction":34},"Enzyme protein","Speeds up chemical reactions",{"id":336,"data":1820,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1821,"multiChoiceQuestion":1822,"multiChoiceCorrect":1824,"multiChoiceIncorrect":1826,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1830,"matchPairsPairs":1831},[333,337],[1823],"What determines the shape and function of a protein?",[1825],"The sequence of amino acids",[1827,1828,1829],"The temperature of the environment","Regulatory hormones","The type of cell",[178],[1832],{"left":1833,"right":1834,"direction":34},"Amino Acids","Their sequence determines the shape and function of a protein",{"id":1836,"data":1837,"type":24,"maxContentLevel":34,"version":24,"reviews":1840},"c8db2f4f-180e-478c-b56b-94dc0221cc4d",{"type":24,"markdownContent":1838,"audioMediaId":1839},"Proteins also provide structural support to cells and tissues. For instance, **collagen** is a protein that gives strength and structure to skin, bones, and connective tissues.\n\n![Graph](image://2a25ce6e-062a-4ec9-b26c-ccd89726309f \"Collagen. Image by Laboratoires Servier (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\n**Keratin**, another protein, is found in hair, nails, and the outer layer of skin, providing protection and durability.\n\nThese structural proteins help maintain the shape and integrity of cells and tissues, which is crucial for the proper functioning of an organism.\n\n**Transport proteins** are another important type of protein. They help move substances across cell membranes and throughout the body.\n\n**Hemoglobin**, a transport protein in red blood cells, carries oxygen from the lungs to the rest of the body and brings carbon dioxide back to the lungs for exhalation. This transport of gases is vital for respiration and energy production in cells.\n\n![Graph](image://1ef4516d-d3be-4262-b9fe-cbca8532502b \"Hemoglobin (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")","56c41105-18d8-482f-bb2a-962ec95a228a",[1841,1855,1869],{"id":1842,"data":1843,"type":67,"version":24,"maxContentLevel":34},"6cf38aad-652a-462d-8f21-433ca764e95b",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1844,"multiChoiceCorrect":1846,"multiChoiceIncorrect":1852,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[1845],"What role do proteins play in cells and tissues?",[1847,1848,1849,1850,1851],"Structural support","Act as enzymes","Transport substances","Cell signaling","Immune response",[1853,1854],"Store genetic information","Produce energy",{"id":1856,"data":1857,"type":67,"version":24,"maxContentLevel":34},"ce2349cb-bc94-4ea7-9570-c618f2704da1",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":1858,"matchPairsPairs":1859,"matchPairsShowExamples":6},[178],[1860,1863,1866],{"left":1861,"right":1862,"direction":34},"Transport proteins","Move substances across cell membranes",{"left":1864,"right":1865,"direction":34},"Keratin","Found in hair, nails, outer skin layer",{"left":1867,"right":1868,"direction":34},"Collagen","Provides strength to connective tissues (such as in skin and bones)",{"id":1870,"data":1871,"type":67,"version":24,"maxContentLevel":34},"91bfaceb-d0bb-4749-b517-3ca31c054547",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1872,"multiChoiceCorrect":1874,"multiChoiceIncorrect":1877,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[1873],"What are the specific functions of the protein hemoglobin?",[1875,1876],"Carries oxygen in red blood cells","Brings carbon dioxide back to lungs",[1878,1879,1880],"Regulates blood sugar","Neutralizes foreign invaders","Provides structural support",{"id":1882,"data":1883,"type":24,"maxContentLevel":34,"version":24,"reviews":1886},"168b8cb9-36de-48af-bbb3-c8d42751f135",{"type":24,"markdownContent":1884,"audioMediaId":1885},"Proteins also play a key role in cell signaling and communication.\n\n**Receptor proteins** on the surface of cells bind to **signaling molecules**, such as hormones, and transmit messages into the cell.\n\nThis process helps cells respond to changes in their environment and coordinate activities within the organism.\n\nFor example, insulin is a **regulatory protein** or **hormone**, that controls blood sugar levels by signaling cells to take up glucose.\n\nIn addition to these roles, proteins are involved in the immune response.\n\n**Antibodies** are proteins that recognize and neutralize foreign invaders, such as bacteria and viruses, protecting the body from infections. This defense mechanism is essential for maintaining health and preventing disease.","bebd7bf1-debb-43f4-b6f2-e45c77b4fc4e",[1887],{"id":1888,"data":1889,"type":67,"version":24,"maxContentLevel":34},"6fb28a85-7eb2-403d-8b5e-93654b80d437",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":1890,"matchPairsPairs":1892,"matchPairsShowExamples":6},[1891],"Match the type of protein to its function below:",[1893,1896,1899],{"left":1894,"right":1895,"direction":34},"Antibodies","Recognize and neutralize foreign invaders, protecting the body from infections",{"left":1897,"right":1898,"direction":34},"Receptor proteins","Bind to signalling molecules and transmit messages into the cell",{"left":1900,"right":1901,"direction":34},"Insulin","Controls blood sugar levels by signaling cells to take up glucose.",{"id":1903,"data":1904,"type":24,"maxContentLevel":34,"version":24,"reviews":1907},"40eed6ae-afa3-47a8-93bd-232192115c30",{"type":24,"markdownContent":1905,"audioMediaId":1906},"Proteins are incredibly versatile because they can fold into a wide variety of shapes, allowing them to interact specifically with other molecules.\n\nThis specificity is crucial for the regulation of cellular processes.\n\nFor example, **enzymes** have active sites that bind to specific substrates, ensuring that biochemical reactions occur with precision and efficiency.\n\nMoreover, proteins can change their shape in response to environmental conditions or interactions with other molecules.\n\nThese changes can activate or deactivate the protein's function, providing a mechanism for regulating cellular activities.\n\nFor instance, the binding of a hormone to its receptor can trigger a series of events inside the cell, leading to a specific response.","ac7632ee-1097-40c4-a394-15227de4f1ba",[1908,1926],{"id":1909,"data":1910,"type":67,"version":24,"maxContentLevel":34},"e8d8441a-17b5-435a-83a4-6a848eb463e5",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":1911,"matchPairsPairs":1913,"matchPairsShowExamples":6},[1912],"Match the protein type to an example of that type:",[1914,1917,1920,1923],{"left":1915,"right":1916,"direction":34},"Enzymes","Digestive proteins that break down food",{"left":1918,"right":1919,"direction":34},"Structural Proteins","Collagen and keratin",{"left":1921,"right":1922,"direction":34},"Transport Proteins","Hemoglobin",{"left":1924,"right":1925,"direction":34},"Regulatory Proteins","Insulin ",{"id":1927,"data":1928,"type":67,"version":24,"maxContentLevel":34},"11d76885-1ea9-4449-ae1c-066519ae9043",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1929,"multiChoiceCorrect":1931,"multiChoiceIncorrect":1933,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1930],"Which of the following are examples of signaling molecules?",[1932],"Hormones",[1867,1864,1922],{"id":1935,"data":1936,"type":25,"version":34,"maxContentLevel":34,"summaryPage":1938,"introPage":1946,"pages":1952},"2d49d7c4-43c2-4602-8cd5-3653fac77ff5",{"type":25,"title":1937},"Carbohydrates",{"id":1939,"data":1940,"type":34,"maxContentLevel":34,"version":24},"2e3a5a94-2f00-4b5e-b2a8-6b4f3c476db5",{"type":34,"summary":1941},[1942,1943,1944,1945],"Carbs power cells by breaking down into glucose.","Starches and glycogen store energy for later use.","Cellulose gives plants strength and structure.","Glycoproteins help cells recognize and communicate.",{"id":1947,"data":1948,"type":53,"maxContentLevel":34,"version":24},"b45d9644-2fd4-4fa9-8315-44bb984cbf26",{"type":53,"intro":1949},[1950,1951],"How do plants store energy using carbohydrates?","What role does cellulose play in plant structure?",[1953,1999,2029,2050],{"id":1954,"data":1955,"type":24,"maxContentLevel":34,"version":24,"reviews":1958},"0bf094f0-209b-42d2-b596-c87bbaaf1f9a",{"type":24,"markdownContent":1956,"audioMediaId":1957},"We already touched upon carbohydrates in the orb focused on **carbon.** This section is going to go into a little more depth.\\\n\\\nCarbohydrates are essential molecules that play a crucial role in the characteristics of life, particularly in energy processing, growth and development, and response to stimuli.\n\nThey are composed of **carbon**, **hydrogen**, and **oxygen**, and are found in foods like fruits, vegetables, grains, and dairy products.\n\n![Graph](image://b52cfb6d-8ae1-4993-b5ce-e5488a484d5f \"Assorted grains. Image by Fir0002 (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")\n\nOne of the primary roles of carbohydrates is to provide energy.\n\n**Simple carbohydrates**, such as glucose, are quickly absorbed by the body and used as a direct source of energy. **Glucose** is especially important because it is the main fuel for our cells.\n\nDuring **cellular respiration**, glucose is broken down to produce adenosine triphosphate (ATP), which cells use to power various activities, such as muscle contraction and nerve function.\n\nThis immediate energy supply is vital for everyday activities and overall bodily functions.","7d17ef3b-a57f-4126-8293-fb3d5765dca5",[1959,1968,1981],{"id":1960,"data":1961,"type":67,"version":24,"maxContentLevel":34},"0bb86072-cd0e-43cd-ba77-1f57ce756b0b",{"type":67,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":1962,"binaryCorrect":1964,"binaryIncorrect":1966},[1963],"What is the composition of carbohydrate?",[1965],"Composed of carbon, hydrogen, and oxygen",[1967],"Composed of carbon and hydrogen",{"id":1969,"data":1970,"type":67,"version":24,"maxContentLevel":34},"a64ab6dd-a2fd-436c-9986-cfa56be06eb8",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":1971,"multiChoiceCorrect":1973,"multiChoiceIncorrect":1977,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[1972],"Which of the following statements are true about simple carbohydrates?",[1974,1975,1976],"Quickly absorbed by the body","Used as a direct source of energy","Glucose is an example",[1978,1979,1980],"Slowly absorbed by the body","Used for long-term energy storage","Starch is an example",{"id":1982,"data":1983,"type":67,"version":24,"maxContentLevel":34},"3421a474-8c79-4616-bbf0-06e05a0d88ec",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":1984,"multiChoiceQuestion":1987,"multiChoiceCorrect":1989,"multiChoiceIncorrect":1991,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1995,"matchPairsPairs":1996},[1985,1986],"70286092-01dd-448a-ae4c-16d071d29651","41969ac0-f2c8-43d6-8265-9a6482d02147",[1988],"What is cellular respiration?",[1990],"Process where glucose is broken down to produce ATP",[1992,1993,1994],"Process where ATP is converted to glucose","Process where oxygen is produced","Process where proteins are synthesized",[178],[1997],{"left":1998,"right":1990,"direction":34},"Cellular Respiration",{"id":2000,"data":2001,"type":24,"maxContentLevel":34,"version":25,"reviews":2004},"b815d990-f483-463a-8d19-af614a9fa991",{"type":24,"markdownContent":2002,"audioMediaId":2003},"Carbohydrates also come in more complex forms, such as starches and glycogen, which serve as energy storage molecules.\n\n**Plants store energy in the form of starch**, which is found in foods like potatoes, rice, and corn.\n\n![Graph](image://b990e2f8-0991-4147-94a2-a39d1dbe387d \"Cornstarch mixed with water. Image by kalaya (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nWhen we eat these foods, our bodies break down the starch into glucose, which can then be used for energy.\n\nAnimals, including humans, **store energy in the form of glycogen**, primarily in the liver and muscles.\n\nWhen the body needs energy, glycogen is broken down into glucose to maintain blood sugar levels and provide fuel for cells.\n\nThis stored energy is crucial for sustaining bodily functions during periods when food intake is low.","93f934ca-5c29-410b-ae20-02b2ce792a90",[2005,2018],{"id":2006,"data":2007,"type":67,"version":24,"maxContentLevel":34},"ccd7e5dc-2ebb-4f9c-bc3d-9ee5ca1841da",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2008,"multiChoiceCorrect":2010,"multiChoiceIncorrect":2014,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2009],"Which of the following statements are true about starch?",[2011,2012,2013],"Energy storage form in plants","Found in potatoes, rice, and corn","Broken down into glucose when consumed",[2015,2016,2017],"Energy storage form in animals","Found in meat","Not broken down into glucose",{"id":2019,"data":2020,"type":67,"version":24,"maxContentLevel":34},"f398ce8d-4d21-468c-9ff4-cf2214f3b335",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2021,"multiChoiceCorrect":2023,"multiChoiceIncorrect":2027,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2022],"Which of the following statements are true about glycogen?",[2024,2025,2026],"Energy storage form in animals and humans","Stored primarily in the liver and muscles","Broken down into glucose when energy is needed",[2011,2028,2017],"Stored in the blood",{"id":2030,"data":2031,"type":24,"maxContentLevel":34,"version":24,"reviews":2034},"8787d288-efea-4b82-8e77-04ada618caee",{"type":24,"markdownContent":2032,"audioMediaId":2033},"In addition to energy storage, carbohydrates provide structural support, which is closely related to the growth and development of living organisms.\n\nFor example, as we saw in the previous orb on carbon, **cellulose** is a carbohydrate that makes up the cell walls of plants. It gives plants their rigidity and strength, allowing them to stand upright and grow.\n\nAlthough humans cannot digest cellulose, it is an important part of our diet as dietary fiber, which helps maintain a healthy digestive system by promoting regular bowel movements and preventing constipation.\n\n![Graph](image://6813c562-6301-4230-b328-cc0e3399dade \"The outer husks of corn, primarily made from cellulose, cannot be digested by humans. Starr-160707-0054-Zea mays-Hawaiian Supersweet hybrid ears harvested-Hawea Pl Olinda-Maui (29632280186) by Forest and Kim Starr (CC BY 3.0 us) \u003Chttps://creativecommons.org/licenses/by/3.0/us/deed.en>, via Wikimedia Commons\")","d7715bea-8c74-470c-885f-5e96da2f9aad",[2035],{"id":1748,"data":2036,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2037,"multiChoiceQuestion":2038,"multiChoiceCorrect":2040,"multiChoiceIncorrect":2042,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2046,"matchPairsPairs":2047},[1749,1750,1745],[2039],"What is the role of dietary fiber in humans?",[2041],"Promotes regular bowel movements",[2043,2044,2045],"Provides immediate energy","Forms cell walls","Acts as an enzyme",[178],[2048],{"left":2049,"right":2041,"direction":34},"Dietary Fiber",{"id":2051,"data":2052,"type":24,"maxContentLevel":34,"version":34,"reviews":2055},"9f762ea6-4ddf-497f-8af9-7c6025f553f2",{"type":24,"markdownContent":2053,"audioMediaId":2054},"Carbohydrates also play a role in **cell recognition and communication**.\n\nOn the surface of cells, carbohydrates are often attached to proteins and lipids, forming structures known as **glycoproteins** and **glycolipids**.\n\n![Graph](image://c5c55821-1ad8-4459-a0da-3731b4fcf04c \"A cell membrane with glycoproteins and glycolipids attatched. Image: OpenStax, CC BY 4.0 \u003Chttps://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons\")\n\nThese structures help cells recognize and interact with each other, which is important for the immune system and other cellular processes.\n\nFor instance, they help the immune system distinguish between the body's own cells and foreign invaders, such as bacteria and viruses.","0892db10-7bb9-4252-b592-2217b7891782",[2056,2068],{"id":2057,"data":2058,"type":67,"version":34,"maxContentLevel":34},"cd2eac9e-83fd-4500-b18b-96572946deec",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2059,"multiChoiceCorrect":2061,"multiChoiceIncorrect":2065,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2060],"Which of the below are the primary functions of complex carbohydrates?",[2062,2063,2064],"Serve as energy storage molecules","Structural support in plants","Role in cell recognition and communication",[2066,2067,1848],"Provide immediate energy","Transport of substancies",{"id":2069,"data":2070,"type":67,"version":24,"maxContentLevel":34},"5ec63d50-c10d-4aed-b4a1-4591ba2f223c",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2071,"multiChoiceCorrect":2073,"multiChoiceIncorrect":2076,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2072],"On the surface of cells, carbohydrates are often attached to proteins and lipids, forming new structures. What are these structures called, and what is their primary function?",[2074,2075],"Glycoproteins and glycolipids","Communication fuction: they help cells recognize and interact with each other",[2077,2078,2079,2080],"Proteolipids and liposaccharides","Structural function: they provide structural support to the cell membrane","Lipoglycans and protein sugars","Energy storage function: they store energy for the cell to use later",{"id":2082,"data":2083,"type":25,"version":24,"maxContentLevel":34,"summaryPage":2085,"introPage":2093,"pages":2099},"a6c82aec-257a-403f-aa94-1952e7d670e7",{"type":25,"title":2084},"Nucleic Acids",{"id":2086,"data":2087,"type":34,"maxContentLevel":34,"version":24},"f5c6fc31-3d5e-44a7-bd7e-5804299843e8",{"type":34,"summary":2088},[2089,2090,2091,2092],"Nucleic acids are chains of smaller units that carry genetic information.","The phosphate group gives them their acidic nature.","The sequence of nitrogen-containing bases in these molecules encodes the instructions for building and running living cells.","Different forms of RNA play specialized roles in translating these instructions into the structure of proteins.",{"id":2094,"data":2095,"type":53,"maxContentLevel":34,"version":24},"654af494-5391-40d7-9ab2-84120d512837",{"type":53,"intro":2096},[2097,2098],"What makes DNA's structure stable for storing genetic info?","How does mRNA help in protein production?",[2100,2139,2156,2175],{"id":2101,"data":2102,"type":24,"maxContentLevel":34,"version":24,"reviews":2105},"3911e332-01ce-4da1-bc34-13138c2d4dbc",{"type":24,"markdownContent":2103,"audioMediaId":2104},"**Nucleic acids** are essential molecules in all living things because they store and pass on genetic information, guiding how cells function and reproduce.\n\nThe two main types of nucleic acids are **DNA** (deoxyribonucleic acid) and **RNA** (ribonucleic acid).\n\nThe \"**acid**\" in nucleic acids comes from the phosphate group, which can **lose a hydrogen ion**, leaving it with a negative charge.\n\nThis negative charge gives the molecule its acidic properties and allows it to interact with water and other charged molecules in the cell.\n\nThis interaction is important for the nucleic acid's ability to dissolve in water and function properly in the cell.","6e610a4c-07b1-4f32-9e85-dc8d684ea0b6",[2106,2116,2132],{"id":2107,"data":2108,"type":67,"version":24,"maxContentLevel":34},"05db777a-bc75-4bf5-86b6-2380ce61a662",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2109,"multiChoiceCorrect":2111,"multiChoiceIncorrect":2113,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2110],"What are the two primary types of nucleic acids?",[2112],"DNA and RNA",[2114,2115],"DNA and ATP","RNA and ATP",{"id":1684,"data":2117,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2118,"multiChoiceQuestion":2119,"multiChoiceCorrect":2121,"multiChoiceIncorrect":2123,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2127,"matchPairsPairs":2128},[1679,1682,1683],[2120],"What gives nucleic acids their acidic properties?",[2122],"Phosphate group",[2124,2125,2126],"Nitrogenous bases","Sugar group","Hydrogen bonds",[178],[2129],{"left":2130,"right":2131,"direction":34},"Phosphate Group","Gives nucleic acid its acidic properties",{"id":2133,"data":2134,"type":67,"version":24,"maxContentLevel":34},"8f5a245a-1bb7-4dfe-aaf1-7d14b7c99dec",{"type":67,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":2135,"activeRecallAnswers":2137},[2136],"What does the acidic property of nucleic acid allow its molecules to do?",[2138],"Gives it a negative charge, enabling interaction with water and other charged molecules in the cell",{"id":2140,"data":2141,"type":24,"maxContentLevel":34,"version":24,"reviews":2144},"049e6906-ebb6-4e7a-b4d4-7a9180dbecaa",{"type":24,"markdownContent":2142,"audioMediaId":2143},"Nucleic acids are made up of smaller units called **nucleotides**. Each nucleotide has three parts: a sugar, a phosphate group, and a nitrogenous base.\n\n![Graph](image://9a072f60-44be-475e-aeb5-77e9856af9d6 \"The structure of nucleotides. Image: OpenStax College, CC BY 3.0 \u003Chttps://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons\")\n\nDNA is structured like a twisted ladder, known as a **double helix**. The sugar and phosphate groups form the sides of the ladder, creating a long chain, while the nitrogenous bases form the rungs.\n\nThe term \"nitrogenous\" refers to the fact that these bases (the rungs on the ladder) contain nitrogen atoms.","222c5ffe-eaec-4711-8490-40833f01df94",[2145],{"id":2146,"data":2147,"type":67,"version":24,"maxContentLevel":34},"35fc501a-837e-4b46-bcd1-fdb0325e5ddb",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2148,"multiChoiceCorrect":2150,"multiChoiceIncorrect":2153,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2149],"What are the components of a nucleotide?",[2151,2122,2152],"Sugar","Nitrogenous base",[2154,2155],"Lipid","Amino acid",{"id":2157,"data":2158,"type":24,"maxContentLevel":34,"version":24,"reviews":2161},"acbbfa28-a77b-47ed-b72c-9e357eeb1a5e",{"type":24,"markdownContent":2159,"audioMediaId":2160},"The nitrogenous bases are the key to the genetic code because they pair up in specific ways to store information. In **DNA**, the bases are adenine (A), thymine (T), cytosine (C), and guanine (G).\n\nIn **RNA**, thymine is replaced by uracil (U).\n\n![Graph](image://af888ad4-ae4a-4b1b-8695-4d8b9bd5bbc5 \"The nitrogenous base pairings. Image: Sponk, CC BY-SA 3.0 \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nIn the ladder structure of DNA, adenine pairs with thymine, and cytosine pairs with guanine.\n\nThis stable structure allows DNA to securely store genetic information. When needed, the two strands of the DNA can separate to allow the information to be copied or used to make proteins.\n\n![Graph](image://34c2582c-7f75-4296-883a-110341ab3d2b \"Nucleic acids - Transcription by Laboratoires Servier (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")","0f9a24e0-3dd3-44f5-b043-db7fe120d748",[2162],{"id":2163,"data":2164,"type":67,"version":24,"maxContentLevel":34},"523e6f2e-df3f-45d1-96eb-01033fa98dc1",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2165,"multiChoiceCorrect":2167,"multiChoiceIncorrect":2172,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2166],"Which bases are found in DNA?",[2168,2169,2170,2171],"Adenine","Thymine","Cytosine","Guanine",[2173,2174],"Uracil","Lysine",{"id":2176,"data":2177,"type":24,"maxContentLevel":34,"version":24,"reviews":2180},"ba455abd-5665-4a7a-91a3-b883f3731c31",{"type":24,"markdownContent":2178,"audioMediaId":2179},"**RNA**, on the other hand, is usually single-stranded and more flexible. Because of this flexibility, RNA can fold into various shapes, enabling it to perform different functions within the cell.\n\nThere are three main types of RNA, each with a specific role:\n\n**Messenger RNA** (mRNA): mRNA carries genetic instructions from DNA to the ribosomes, where proteins are synthesized. It acts as a template for assembling amino acids in the correct order to produce a specific protein.\n\n**Ribosomal RNA** (rRNA): rRNA is a key component of ribosomes, the cellular structures where proteins are made. rRNA helps to align the mRNA and the ribosomes and catalyzes the formation of the bonds between amino acids.\n\n**Transfer RNA** (tRNA): tRNA transports amino acids to the ribosome during protein synthesis. Each tRNA molecule recognizes specific sequences of mRNA and ensures that the correct amino acid is added to the growing protein chain.","dc1f3eb8-52a4-4c0f-a403-e001fa65f6dc",[2181,2192,2204],{"id":2182,"data":2183,"type":67,"version":24,"maxContentLevel":34},"b2de381e-7a29-48e4-9699-7e5a8194e82c",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2184,"multiChoiceCorrect":2186,"multiChoiceIncorrect":2188,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2185],"How is RNA usually structured?",[2187],"Single-stranded",[2189,2190,2191],"Double-stranded","Triple-stranded","Circular form",{"id":2193,"data":2194,"type":67,"version":24,"maxContentLevel":34},"557eb080-1616-4d4c-ad56-06c74bbf9f69",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2195,"multiChoiceCorrect":2197,"multiChoiceIncorrect":2201,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2196],"Which of the below are the main types of RNA?",[2198,2199,2200],"mRNA","rRNA","tRNA",[2202,2203],"dRNA","bRNA",{"id":2205,"data":2206,"type":67,"version":24,"maxContentLevel":34},"3c266f46-6689-49a2-9e21-36fe740b3261",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":2207,"matchPairsPairs":2209,"matchPairsShowExamples":6},[2208],"Match the pair below:",[2210,2213,2216,2219],{"left":2211,"right":2212,"direction":34},"Messenger RNA (mRNA)","Template for assembling amino acids",{"left":2214,"right":2215,"direction":34},"Ribosomal RNA (rRNA)","Aligns mRNA and ribosomes",{"left":2217,"right":2218,"direction":34},"Transfer RNA (tRNA)","Transports amino acids to ribosome",{"left":2220,"right":2221,"direction":34},"Ribosome","Cellular structure where proteins are made",{"id":2223,"data":2224,"type":25,"version":25,"maxContentLevel":34,"summaryPage":2226,"introPage":2234,"pages":2240},"774797b5-0925-4fc4-979d-11c4730e5473",{"type":25,"title":2225},"Water",{"id":2227,"data":2228,"type":34,"maxContentLevel":34,"version":24},"e6c01c1b-b4e5-4186-b040-e12750c346ff",{"type":34,"summary":2229},[2230,2231,2232,2233],"Water's polarity makes it a great solvent for substances.","High specific heat stabilizes temperatures in organisms and environments.","Cohesion and adhesion enable water movement in plants.","Water buffers pH, crucial for enzyme function.",{"id":2235,"data":2236,"type":53,"maxContentLevel":34,"version":24},"66a33b29-13f9-49f7-b083-05d149685f63",{"type":53,"intro":2237},[2238,2239],"What makes water such a great solvent?","How does water help plants get nutrients?",[2241,2280,2324],{"id":2242,"data":2243,"type":24,"maxContentLevel":34,"version":24,"reviews":2246},"bebf057e-c813-404a-a719-d47e104c46b1",{"type":24,"markdownContent":2244,"audioMediaId":2245},"We’re going to briefly move away from the organic molecules crucial to life to examine a fundamental molecule that will enhance your understanding of later sections, such as lipids. This molecule is **water**.\n\nWater is essential for life due to its unique properties that directly support living organisms.\n\nOne of the key characteristics of water is its **polarity**. A water molecule is made up of one oxygen atom and two hydrogen atoms. These atoms share electrons, but not equally, which gives the oxygen side of the molecule a slight negative charge and the hydrogen side a slight positive charge.\n\n![Graph](image://befaa48c-afa2-4395-8210-44bd7f4356a7 \"Water molecule. The oxygen side of the molecule a slight negative charge and the hydrogen side a slight positive charge. Image: Riccardo Rovinetti, CC BY-SA 3.0 \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nThis makes water a **polar molecule**, meaning it has a positive and a negative side, similar to a magnet.\n\nBecause of its polarity, water can form hydrogen bonds with other water molecules and with other polar substances. These bonds are weak attractions that allow water to dissolve many substances, making it an excellent solvent.\n\nFor example, when salt is added to water, the water molecules surround and separate the salt's ions, causing the salt to dissolve.\n\nThis ability to dissolve substances is crucial for transporting nutrients and removing waste in living organisms, ensuring that cells get the materials they need to function and stay healthy.","5112ffe4-7266-4754-a9ce-4af64d79d298",[2247,2267],{"id":2248,"data":2249,"type":67,"version":24,"maxContentLevel":34},"12fb5a35-56f9-403d-9f4e-8c459cbc241e",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2250,"multiChoiceQuestion":2254,"multiChoiceCorrect":2256,"multiChoiceIncorrect":2258,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2262,"matchPairsPairs":2263},[2251,2252,2253],"9b4d45ad-9235-493e-a258-6c79d96a6c42","11e8096f-c6ff-471e-b2fd-a9262d58cd0c","6913c49b-ce43-4e15-b77a-1fb70d1f182f",[2255],"What enables water to dissolve many substances?",[2257],"Hydrogen Bonds",[2259,2260,2261],"Cohesion","Adhesion","Capillary Action",[178],[2264],{"left":2265,"right":2266,"direction":34},"Hydrogen bonding between polar molecules","Enables water to dissolve many substances",{"id":2268,"data":2269,"type":67,"version":24,"maxContentLevel":34},"4ac07d8b-e5fa-4da3-8513-442fa1ff5f1a",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2270,"multiChoiceCorrect":2272,"multiChoiceIncorrect":2276,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2271],"Which of the following are true about a water molecule?",[2273,2274,2275],"Made up of one oxygen atom and two hydrogen atoms","Has a slight negative charge on oxygen side","Has a slight positive charge on hydrogen side",[2277,2278,2279],"Made up of two oxygen atom and one hydrogen atoms","Has a slight positive charge on oxygen side","Has a slight negative charge on hydrogen side",{"id":2281,"data":2282,"type":24,"maxContentLevel":34,"version":25,"reviews":2285},"896b309f-6da9-4663-949f-d5f60214ce1f",{"type":24,"markdownContent":2283,"audioMediaId":2284},"Water also has a **high specific heat capacity**, meaning it can absorb a lot of heat before its temperature increases. This property helps stabilize temperatures in organisms and their environments.\n\nFor instance, the large amounts of water in the human body **help maintain a stable internal temperature**, which is vital for enzymes and metabolic processes to function properly.\n\nAnother important feature of water is its **cohesion** and **adhesion**.\n\n**Cohesion** is the ability of water molecules to stick to *other water molecules*, which creates **surface tension**.\n\nThis property is illustrated by the way small insects, like water striders, can walk on water without sinking. In living organisms, this surface tension is important for processes like the movement of water in plants.\n\n![Graph](image://2380ba8e-060d-4eae-b839-83d154344d85 \"Gerridae on a lake. Image by Olexandr Ostrovyi (CC BY 4.0) \u003Chttps://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons\")\n\n**Adhesion**, on the other hand, is water's ability to stick to *different* substances, which, along with cohesion, enables capillary action. In plants, capillary action helps water travel from the roots to the leaves, which is essential for transporting nutrients and maintaining plant health.\n\n![Graph](image://cd79fda1-0cfd-4c13-ac9e-5be40ff79298 \"Mangrove plant roots provides an island in the water (Public domain), via Wikimedia Commons\")","8b4afe1d-2789-411a-b8bd-6b6bf741e198",[2286,2300,2315],{"id":2251,"data":2287,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2288,"multiChoiceQuestion":2289,"multiChoiceCorrect":2291,"multiChoiceIncorrect":2293,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2295,"matchPairsPairs":2296},[2248,2252,2253],[2290],"What property of water helps stabilize temperatures in organisms and their environments?",[2292],"High heat capacity",[2294,2259,2260],"Polarity",[178],[2297],{"left":2298,"right":2299,"direction":34},"High Heat Capacity","Enables water to stabilize temperatures in organisms and their environments",{"id":2253,"data":2301,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2302,"multiChoiceQuestion":2303,"multiChoiceCorrect":2305,"multiChoiceIncorrect":2307,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2311,"matchPairsPairs":2312},[2248,2251,2252],[2304],"What do the cohesive and adhesive properties of water enable in plants?",[2306],"Water travelling from roots to leaves (capillary action)",[2308,2309,2310],"Regulation of leaf temperature (temperature regulation)","Formation of protective waxy coatings on leaves","Maintenance of plant rigidity",[178],[2313],{"left":2259,"right":2314,"direction":34},"Along with adhesion, enables capillary action in plants",{"id":2316,"data":2317,"type":67,"version":25,"maxContentLevel":34},"41125665-e2d1-4fca-b756-7471a95f8a2c",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":2318,"matchPairsPairs":2319,"matchPairsShowExamples":6},[178],[2320,2322],{"left":2260,"right":2321,"direction":34},"Water molecules' ability  to stick to other substances",{"left":2259,"right":2323,"direction":34},"Water molecules' ability stick to each other",{"id":2325,"data":2326,"type":24,"maxContentLevel":34,"version":24,"reviews":2329},"d420aee9-04e9-4a6a-8325-a9aae6dfc70f",{"type":24,"markdownContent":2327,"audioMediaId":2328},"Finally, water helps **maintain pH balance** in living organisms. pH measures how acidic or basic a solution is, and maintaining a stable pH is crucial for life.\n\n![Graph](image://bfddb423-7b46-47f6-b6bb-a7dd047d8370 \"216 pH Scale-01 by OpenStax College (CC BY 3.0) \u003Chttps://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons\")\n\nWater acts as a **buffer**, absorbing excess hydrogen or hydroxide ions by surrounding them with water molecules, which helps to keep pH levels stable.\n\nThis is important for maintaining the proper conditions for enzymes and other proteins to function, such as in human blood, where a stable pH of around 7.4 is necessary for the body to function effectively.","37cfe8e6-64ea-45d5-bc5e-4600f738d189",[2330,2345],{"id":2252,"data":2331,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2332,"multiChoiceQuestion":2333,"multiChoiceCorrect":2335,"multiChoiceIncorrect":2337,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2340,"matchPairsPairs":2341},[2248,2251,2253],[2334],"What is the consequence of water's buffering capacity?",[2336],"Maintains pH balance",[2338,2266,2339],"Creates surface tension","Can absorb a lot of heat before temperature increases",[178],[2342],{"left":2343,"right":2344,"direction":34},"Buffering Capacity","Results in water's ability to maintain pH balance",{"id":1682,"data":2346,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2347,"multiChoiceQuestion":2348,"multiChoiceCorrect":2350,"multiChoiceIncorrect":2352,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2356,"matchPairsPairs":2357},[1679,1683,1684],[2349],"Why does salt dissolve in water?",[2351],"Due to water's polarity",[2353,2354,2355],"Due to water's cohesion","Due to water's adhesion","Due to water's buffering capacity",[178],[2358],{"left":2359,"right":2360,"direction":34},"Salt","Dissolves in water due to water's polarity",{"id":2362,"data":2363,"type":25,"version":34,"maxContentLevel":34,"summaryPage":2365,"introPage":2373,"pages":2379},"05f9985f-aa29-42b7-b552-8b67e23db47e",{"type":25,"title":2364},"Lipids",{"id":2366,"data":2367,"type":34,"maxContentLevel":34,"version":24},"ef7c6279-bc36-4695-9622-82aeae09c6b2",{"type":34,"summary":2368},[2369,2370,2371,2372],"Lipids store energy as fats with glycerol and fatty acids.","Phospholipids form cell membranes with hydrophilic heads and tails.","Steroids stabilize cell membranes and act as signaling molecules.","Lipids help cells communicate by influencing gene expression.",{"id":2374,"data":2375,"type":53,"maxContentLevel":34,"version":24},"b12dffbb-5643-41aa-90b1-11671cda8af7",{"type":53,"intro":2376},[2377,2378],"How do lipids store energy in the body?","What role do phospholipids play in cell membranes?",[2380,2427,2481,2509],{"id":2381,"data":2382,"type":24,"maxContentLevel":34,"version":24,"reviews":2385},"eb1395ed-33af-4507-b3a4-b7ce4245bc24",{"type":24,"markdownContent":2383,"audioMediaId":2384},"**Lipids** are a group of molecules that don't mix well with water, making them essential for many biological functions.\n\nThese molecules are mainly made up of hydrogen and carbon atoms.\n\nBecause of this composition, lipids are **nonpolar**, meaning they don't have a positive or negative charge that would allow them to interact with water molecules.\n\nWater is polar, which means it has regions of slight positive and negative charge, allowing water molecules to stick together.\n\nSince lipids are nonpolar, they don't interact well with water and, therefore, do not dissolve in it. Instead, they separate from water, similar to how oil separates from water in a mixture.\n\n![Graph](image://c43a6f4d-57b1-4fff-9d2d-477fdf7624c0 \"Oil separating from water. Image by Roger McLassus 1951 (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")\n\nThis property is what makes lipids useful for **forming barriers**, such as **cell membranes**, and storing energy in the body.\n\nBesides storing energy and forming membranes, lipids also **insulate and protect**. For example, a layer of fat beneath the skin helps animals maintain their body temperature by reducing heat loss.\n\nAdditionally, lipids cushion organs, providing a protective layer that absorbs shock.","a94766fb-4d2e-4ae2-b1c4-5ded3975fb00",[2386,2401,2416],{"id":1683,"data":2387,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2388,"multiChoiceQuestion":2389,"multiChoiceCorrect":2391,"multiChoiceIncorrect":2393,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2397,"matchPairsPairs":2398},[1679,1682,1684],[2390],"What is the definition of lipids?",[2392],"Group of molecules that don't mix well with water (nonpolar)",[2394,2395,2396],"Group of molecules that mix well with water","Group of molecules that are polar","Group of molecules that are hydrophilic",[178],[2399],{"left":2364,"right":2400,"direction":34},"Do not mix well with water (nonpolar)",{"id":1790,"data":2402,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2403,"multiChoiceQuestion":2404,"multiChoiceCorrect":2406,"multiChoiceIncorrect":2408,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2412,"matchPairsPairs":2413},[1787,1791],[2405],"What are lipids mainly made up of?",[2407],"Hydrogen and carbon atoms",[2409,2410,2411],"Oxygen and nitrogen atoms","Carbon and nitrogen atoms","Hydrogen and oxygen atoms",[178],[2414],{"left":2364,"right":2415,"direction":34},"Mainly made up of hydrogen and carbon atoms",{"id":2417,"data":2418,"type":67,"version":24,"maxContentLevel":34},"7833a032-b092-4e13-90a6-571bc83f2e81",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2419,"multiChoiceCorrect":2421,"multiChoiceIncorrect":2423,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2420],"What are lipids useful for?",[2422],"Forming barriers and storing energy",[2424,2425,2426],"Forming proteins","Transportation","Working as enzymes",{"id":2428,"data":2429,"type":24,"maxContentLevel":34,"version":24,"reviews":2432},"38e22e34-e8d5-4afe-95b2-4782bab14e3a",{"type":24,"markdownContent":2430,"audioMediaId":2431},"The main types of lipids include: **fats**, **oils**, **waxes**, **phospholipids**, and **steroids**, each with its own important role in living organisms.\n\nOne key function of lipids is **storing energy**.\n\nFats, also called **triglycerides**, are the primary way animals store energy.\n\nA fat molecule consists of a glycerol backbone connected to **three fatty acid chains**. These **fatty acids** can be either saturated or unsaturated.\n\n![Graph](image://24c88545-a002-4e00-8516-248106858c5a \"Butter and Oil - NCI Visuals Online (Public domain), via Wikimedia Commons\")\n\n**Saturated fatty acids** have no double bonds between the carbon atoms, so they are fully saturated with hydrogen atoms. This makes them straight, allowing them to pack tightly together, which is why saturated fats are usually solid at room temperature, like butter.\n\n**Unsaturated fatty acids**, on the other hand, have one or more double bonds, creating bends in the chain that prevent tight packing, making them liquid at room temperature, like olive oil.","38d2f168-b55f-4cbe-ab3f-afe8ef7dc9ef",[2433,2446,2461,2468],{"id":2434,"data":2435,"type":67,"version":24,"maxContentLevel":34},"cac170ca-787a-4cde-96d8-a707a71a94eb",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2436,"multiChoiceCorrect":2438,"multiChoiceIncorrect":2443,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2437],"Which of the following are examples of lipids?",[2439,2440,2441,2442],"Fats","Oils","Waxes","Steroids",[2444,1937,2445],"Amino acids","Nucleic acids",{"id":1749,"data":2447,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2448,"multiChoiceQuestion":2449,"multiChoiceCorrect":2451,"multiChoiceIncorrect":2453,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2457,"matchPairsPairs":2458},[1748,1750,1745],[2450],"What is the primary way animals store energy?",[2452],"Fats (Triglycerides)",[2454,2455,2456],"Proteins (Polypeptides)","Carbohydrates (Polysaccharides)","Nucleic acids (DNA/RNA)",[178],[2459],{"left":2452,"right":2460,"direction":34},"Primary way animals store energy",{"id":2462,"data":2463,"type":67,"version":24,"maxContentLevel":34},"eac76435-6333-4a0d-96be-222960f7b38a",{"type":67,"reviewType":41,"spacingBehaviour":24,"clozeQuestion":2464,"clozeWords":2466},[2465],"Fat modules contain glycerol and 3 fatty acid chains that can be either saturated or unsaturated.",[2467],"3 fatty acid chains",{"id":2469,"data":2470,"type":67,"version":24,"maxContentLevel":34},"3c12d661-62e6-420e-afe5-9b84c0a9fd5a",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2471,"multiChoiceCorrect":2473,"multiChoiceIncorrect":2477,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2472],"Which of the following are characteristics of unsaturated fatty acids?",[2474,2475,2476],"One or more double bonds","Bends in the chain, prevent tight packing","Liquid at room temperature",[2478,2479,2480],"No double bonds","Fully saturated with hydrogen atoms","Solid at room temperature",{"id":2482,"data":2483,"type":24,"maxContentLevel":34,"version":34,"reviews":2486},"b8ea73c1-bee8-4a21-b330-d0e1bd386606",{"type":24,"markdownContent":2484,"audioMediaId":2485},"Phospholipids are another important type of lipid, especially for **forming cell membranes.**\n\nA phospholipid molecule has a glycerol backbone, two fatty acid tails, and a phosphate group.\n\nThe phosphate group is **hydrophilic**, meaning it attracts water, while the fatty acid tails are **hydrophobic**, meaning they repel water.\n\nThis unique structure allows phospholipids to form double layers in water, with the fatty acid tails facing inward and the heads facing outward.\n\n![Graph](image://d96b1f4c-9f72-4c03-abcd-677ebc6d3bf0 \"Phospholipid structure of a cell membrane. Image: TvanBrussel (Copyrighted free use), via Wikimedia Commons\")\n\nThis arrangement **creates the cell membrane**, a barrier that controls what enters and leaves the cell.","715e5f37-7909-41a5-9dbf-8c93fe9022c0",[2487,2498],{"id":2488,"data":2489,"type":67,"version":34,"maxContentLevel":34},"e00f1e7f-036b-453b-a8c4-159c35d4a8d9",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2490,"multiChoiceCorrect":2492,"multiChoiceIncorrect":2495,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2491],"Which two of the following statements about the components of phospholipids are true, allowing phospholipids to form double layers in water?",[2493,2494],"The phosphate group is hydrophilic, attracting water","The two fatty acid tails are hydrophobic, repelling water",[2496,2497],"The two fatty acid tails are hydrophilic, attracting water","The phosphate group is hydrophobic, repelling water",{"id":2499,"data":2500,"type":67,"version":24,"maxContentLevel":34},"0b42429e-a635-4c4c-bc9e-1c340901b985",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2501,"multiChoiceCorrect":2503,"multiChoiceIncorrect":2505,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2502],"Phospholipids form double layers in water. What part of the cell is made of this structure?",[2504],"The cell membrane",[2506,2507,2508],"The nucleus","The nuclear envelope","Produces hormones",{"id":2510,"data":2511,"type":24,"maxContentLevel":34,"version":24,"reviews":2514},"56eb6f9f-31c6-4815-ad56-32ecd3c85118",{"type":24,"markdownContent":2512,"audioMediaId":2513},"**Steroids** are a different kind of lipid with a structure made up of four connected carbon rings.\n\nCholesterol is a well-known steroid that is crucial for cell membrane stability and fluidity.\n\nCholesterol also serves as a building block for **steroid hormones** like **testosterone** and **estrogen**, which regulate many body functions.\n\nAdditionally, **cholesterol** is necessary for producing bile salts that help digest and absorb fats from food.\n\nLipids such as steroids also play a role in **communication between cells**. Some lipids act as signaling molecules, influencing how cells behave.\n\nFor example, steroid hormones derived from cholesterol can enter cells and bind to receptors, causing changes in how genes are expressed and how the cell functions.\n\nThis ability to signal is vital for maintaining balance in the body and coordinating complex biological responses.","c7e98dfd-73dd-471a-bca3-cf9f8a19ab3d",[2515,2529,2543,2556],{"id":1791,"data":2516,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2517,"multiChoiceQuestion":2518,"multiChoiceCorrect":2520,"multiChoiceIncorrect":2522,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2526,"matchPairsPairs":2527},[1787,1790],[2519],"What is the structure of steroids?",[2521],"Made up of four connected carbon rings",[2523,2524,2525],"Made up of three connected carbon rings","Made up of five connected carbon rings","Made up of two connected carbon rings",[178],[2528],{"left":2442,"right":2521,"direction":34},{"id":945,"data":2530,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2531,"multiChoiceQuestion":2532,"multiChoiceCorrect":2534,"multiChoiceIncorrect":2536,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2539,"matchPairsPairs":2540},[941,944,946],[2533],"What role do steroids play in cells?",[2535],"Cell communication",[2537,341,2538],"Energy storage","Carbohydrate metabolism",[178],[2541],{"left":2442,"right":2542,"direction":34},"Play a role in cell communication",{"id":2544,"data":2545,"type":67,"version":24,"maxContentLevel":34},"2ac3e2c8-dc9e-4c21-a408-e7d85f58788f",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2546,"multiChoiceCorrect":2548,"multiChoiceIncorrect":2552,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2547],"Which of the following are examples of steroids?",[2549,2550,2551],"Cholesterol","Testosterone","Estrogen",[2553,2554,2555,1900],"Glycerol","Phosphate","Triglycerides",{"id":2557,"data":2558,"type":67,"version":24,"maxContentLevel":34},"8b0b17ff-8503-4e5c-be72-d15b1a1492c8",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2559,"multiChoiceCorrect":2561,"multiChoiceIncorrect":2565,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2560],"Which of the following are functions of cholesterol?",[2562,2563,2564],"Building block for steroid hormones","Necessary for producing bile salts","Stabilizes cell membrane",[2566,341,2538],"Primary energy storage",{"id":2568,"data":2569,"type":26,"maxContentLevel":34,"version":41,"orbs":2571},"26145198-0e13-4bdb-930e-055f6e5fd146",{"type":26,"title":181,"tagline":2570},"How organisms process energy",[2572,2681],{"id":2573,"data":2574,"type":25,"version":34,"maxContentLevel":34,"summaryPage":2576,"introPage":2584,"pages":2590},"768a3f5b-4473-42f5-84eb-1e14313793b1",{"type":25,"title":2575},"Anabolism and Catabolism",{"id":2577,"data":2578,"type":34,"maxContentLevel":34,"version":24},"c6fc4b9e-0f66-4f71-9b4b-4a8f24ab9247",{"type":34,"summary":2579},[2580,2581,2582,2583],"Metabolism includes anabolism and catabolism for energy management.","Anabolism builds complex molecules, storing energy for growth.","Catabolism breaks down molecules, releasing energy for activities.","Energy balance ensures life processes continue smoothly.",{"id":2585,"data":2586,"type":53,"maxContentLevel":34,"version":24},"abbb05ee-bf68-4247-8e30-12eedafe3ec5",{"type":53,"intro":2587},[2588,2589],"How does your body store energy from food?","What happens to glycogen during exercise?",[2591,2618,2652],{"id":2592,"data":2593,"type":24,"maxContentLevel":34,"version":25,"reviews":2596},"70a653c8-2b4c-414a-8aad-1d7b0876c861",{"type":24,"markdownContent":2594,"audioMediaId":2595},"As we already examined in our tile on the processes of life, metabolism refers to all the chemical reactions that take place within an organism to keep it alive and functioning. These reactions are fundamentally about how the body uses and manages energy.\n\nIn this orb, we're going to quickly recap the two main parts of metabolism: anabolism and catabolism.\n\nAs you may remember, **anabolism** is about storing energy and building the components needed for growth and repair, while **catabolism** is about breaking down those components to release energy when it’s needed.","ed82b95d-cef5-4e89-a77b-963ceca63ba8",[2597,2603],{"id":2598,"data":2599,"type":67,"version":24,"maxContentLevel":34},"83f2ad8f-ecee-4311-b097-f7a902ee6483",{"type":67,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":2600,"activeRecallAnswers":2602},[2601],"Metabolism can be divided into which two main parts?",[2575],{"id":1985,"data":2604,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2605,"multiChoiceQuestion":2606,"multiChoiceCorrect":2607,"multiChoiceIncorrect":2609,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2613,"matchPairsPairs":2614},[1982,1986],[908],[2608],"Building complex molecules from simpler ones (uses energy)",[2610,2611,2612],"Breaking down molecules into simpler ones (releases energy)","Transporting molecules across cell membranes (uses energy)","Producing energy from sunlight (releases energy)",[178],[2615],{"left":2616,"right":2617,"direction":34},"Anabolism","Building complex molecules from simpler ones",{"id":2619,"data":2620,"type":24,"maxContentLevel":34,"version":34,"reviews":2623},"05d68256-802a-4aac-beb3-68dbf40d59f1",{"type":24,"markdownContent":2621,"audioMediaId":2622},"Anabolism involves building things up—like how your body creates complex molecules, such as proteins, from simpler ones.\n\nThis process is essential for growth, repair, and storing energy. For instance, when you eat food, your body breaks it down into simpler substances like amino acids and sugars. These substances are then used to build or repair tissues and to store energy in the form of fat or glycogen for later use.\n\n![Graph](image://9b2e5c1e-3489-4370-9b5e-79e1948689e1 \"Anabolism and Catabolism by Christinelmiller (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\n\\\nA good example of anabolism is when your body uses the glucose (a simple sugar) from the food you eat to build glycogen, a complex carbohydrate that your muscles and liver store as an energy reserve.\n\nThis stored energy can be tapped into when your body needs it, such as during exercise or between meals.\n\nAnabolism requires energy because it’s about constructing larger molecules that your body can use for various functions, such as building muscle or repairing cells.","712b36fc-64c1-4373-8c6f-7c46cd2cf46d",[2624,2639],{"id":1750,"data":2625,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2626,"multiChoiceQuestion":2627,"multiChoiceCorrect":2629,"multiChoiceIncorrect":2631,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2635,"matchPairsPairs":2636},[1748,1749,1745],[2628],"What is glycogen used for in the body?",[2630],"Energy reserve tapped during exercise or between meals",[2632,2633,2634],"Immediate energy source","Structural component of cells","Hormone production",[178],[2637],{"left":2638,"right":2630,"direction":34},"Glycogen",{"id":1056,"data":2640,"type":67,"version":25,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2641,"multiChoiceQuestion":2642,"multiChoiceCorrect":2644,"multiChoiceIncorrect":2645,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2648,"matchPairsPairs":2649},[1053,1057],[2643],"Which process involves converting glucose to glycogen?",[2616],[2646,172,2647],"Catabolism","Fermentation",[178],[2650],{"left":2616,"right":2651,"direction":34},"Process converting glucose to glycogen",{"id":2653,"data":2654,"type":24,"maxContentLevel":34,"version":34,"reviews":2657},"7d93d74c-4dbe-4a9f-afc6-77e1ec2cc1fc",{"type":24,"markdownContent":2655,"audioMediaId":2656},"On the flip side, catabolism is the process of breaking things down. It involves the breakdown of complex molecules into simpler ones, releasing energy that the organism can use immediately.\n\nThis energy is crucial for all your body’s activities, from the involuntary beating of your heart to the voluntary movements of your muscles when you exercise.\n\nWhen you engage in physical activity, your body breaks down the glycogen stored in your muscles into glucose, which is then further broken down to release energy. This energy fuels your muscles and keeps you moving.\n\nCatabolism doesn’t just happen during physical activity; it’s a continuous process, even when you’re at rest. Your body constantly breaks down nutrients to provide a steady supply of energy for all your cells, ensuring that your vital organs continue to function. The energy released during catabolism is what powers everything from your brain’s electrical impulses to the digestion of your food.\n\nUnderstanding these two processes—anabolism and catabolism—helps clarify how your body manages energy. Together, these processes ensure that you have the energy required for daily life.","da2def39-e4b6-44cd-869c-4e9c5805ac40",[2658,2670],{"id":1057,"data":2659,"type":67,"version":25,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2660,"multiChoiceQuestion":2661,"multiChoiceCorrect":2663,"multiChoiceIncorrect":2665,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2666,"matchPairsPairs":2667},[1053,1056],[2662],"What is the definition of catabolism?",[2664],"Breaking down complex molecules into simpler ones (releases energy)",[2608,2611,2612],[178],[2668],{"left":2646,"right":2669,"direction":34},"Breaking down complex molecules into simpler ones",{"id":2671,"data":2672,"type":67,"version":24,"maxContentLevel":34},"5a04792a-4f18-40b1-a7b3-f5c716b11251",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2673,"multiChoiceCorrect":2675,"multiChoiceIncorrect":2677,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2674],"When does catabolism occur?",[2676],"Continuously, even at rest",[2678,2679,2680],"Only during exercise","Only during sleep","Immediately after eating",{"id":2682,"data":2683,"type":25,"version":25,"maxContentLevel":34,"summaryPage":2685,"introPage":2693,"pages":2699},"bcd1a735-528d-4207-93ed-c75dae60e210",{"type":25,"title":2684},"ATP",{"id":2686,"data":2687,"type":34,"maxContentLevel":34,"version":24},"1650f588-ca66-41d1-be76-c16d252f0cb2",{"type":34,"summary":2688},[2689,2690,2691,2692],"ATP is the cell's energy \"cash\".","ATP releases energy by breaking phosphate bonds.","ADP recharges to ATP using energy from food breakdown.","ATP powers muscle contractions and active transport.",{"id":2694,"data":2695,"type":53,"maxContentLevel":34,"version":24},"abb11aa2-729d-4f10-882c-db18d404d60c",{"type":53,"intro":2696},[2697,2698],"What is the chemical make-up of ATP?","How does ATP act as a bridge between catabolic and anabolic reactions?",[2700,2716,2755,2790],{"id":2701,"data":2702,"type":24,"maxContentLevel":34,"version":24,"reviews":2705},"aeee9863-0329-4bcb-b476-8e1fbe44d5c2",{"type":24,"markdownContent":2703,"audioMediaId":2704},"Now you understand the basics of anabolism and catabolism in managing energy.\n\nBut what exactly IS that energy?\n\nYou might remember that earlier, when we talked about metabolism in individual cells, we briefly mentioned ATP as the \"energy cash\" of the cell.\n\nNow, let's explore why ATP is so important and how it connects to what you’ve already learned about the chemicals of life.\n\nThink of ATP as the money your cells use to pay for all the activities they need to perform. Just like you need money to buy groceries or pay bills, your cells need ATP to fuel their various functions.\n\nATP is a small molecule composed of three main parts: **adenine** (which is a type of nitrogenous base, like the ones you encountered when we discussed nucleic acids), **ribose** (a sugar, remember what you learned about carbohydrates?), and three **phosphate groups**.","428d8e15-f04e-4b0e-914d-64bd50f846c3",[2706],{"id":2707,"data":2708,"type":67,"version":24,"maxContentLevel":34},"e63b58cb-25b7-4fd9-8847-28e598911c8c",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2709,"multiChoiceCorrect":2711,"multiChoiceIncorrect":2714,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2710],"Which of the following are components of ATP?",[2168,2712,2713],"Ribose","Three phosphate groups",[2170,897,2169,2715],"Two phosphate groups",{"id":2717,"data":2718,"type":24,"maxContentLevel":34,"version":24,"reviews":2721},"06fb5148-3b45-4e88-9127-2f6b13480f33",{"type":24,"markdownContent":2719,"audioMediaId":2720},"The key to ATP’s role as an energy carrier lies in these **phosphate groups.**\n\nThe **bond between the second and third phosphate groups** is particularly high in energy.\n\nWhen the cell needs energy, it \"spends\" ATP by breaking this bond, releasing energy that can be used immediately for various tasks.\n\nWhen ATP releases this energy, it loses one of its phosphate groups and becomes **ADP** (adenosine diphosphate).\n\nYou can think of ADP as a partially used battery: less powerful than ATP but still capable of being recharged.\n\n![Graph](image://54901909-3480-4fe7-b59b-bf7f62fa724a \"Batteries (Public domain), via Wikimedia Commons\")\n\nThis recharging process happens when a phosphate group is added back to ADP, turning it back into ATP.","19e57fef-c453-4e53-a70e-32833ad6d34c",[2722,2733,2744],{"id":2723,"data":2724,"type":67,"version":24,"maxContentLevel":34},"33715030-fff5-4131-a491-25cb3eec0a6f",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2725,"multiChoiceCorrect":2727,"multiChoiceIncorrect":2729,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2726],"Where is the high-energy bond located in an ATP molecule, which is broken in order to release energy?",[2728],"Between the second and third phosphate groups",[2730,2731,2732],"Between the first and second phosphate groups","Between adenine and ribose","Between ribose and the first phosphate group",{"id":2734,"data":2735,"type":67,"version":24,"maxContentLevel":34},"fde14ae8-5cef-44b6-85a3-f5660805eadb",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2736,"multiChoiceCorrect":2738,"multiChoiceIncorrect":2740,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2737],"What is formed when ATP loses a phosphate group?",[2739],"ADP (Adenosine Diphosphate)",[2741,2742,2743],"AMP (Adenosine Monophosphate)","GTP (Guanosine Triphosphate)","CTP (Cytidine Triphosphate)",{"id":2745,"data":2746,"type":67,"version":24,"maxContentLevel":34},"0de77b4b-5a97-4d83-9f7c-fea1bfbca2f7",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2747,"multiChoiceCorrect":2749,"multiChoiceIncorrect":2751,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2748],"How is ADP described in comparison to ATP?",[2750],"Less powerful but rechargeable",[2752,2753,2754],"More powerful and non-rechargeable","Equally powerful and non-rechargeable","Less powerful and non-rechargeable",{"id":2756,"data":2757,"type":24,"maxContentLevel":34,"version":25,"reviews":2760},"073b6365-1917-40f2-9288-b2e667f41e5a",{"type":24,"markdownContent":2758,"audioMediaId":2759},"The process described in this orb itself requires energy, and here’s where it ties back to what you’ve already learned: **the energy needed to recharge ATP** comes from the catabolic reactions that break down food molecules, such as glucose, during **cellular respiration**.\n\nATP is like a middleman, connecting the energy released from catabolism with the energy needed for anabolism.\n\nWhen your body breaks down carbohydrates, proteins, or fats, the energy released during these catabolic processes is captured and stored in ATP molecules.\n\nThese ATP molecules then provide the energy necessary for anabolic processes, such as synthesizing proteins from amino acids.\n\nFurthermore, the versatility of ATP comes from its ability to provide energy for a wide range of cellular activities. For instance, ATP is essential for muscle contractions. It also powers chemical reactions that occur within your cells.\n\nRemember how enzymes are proteins that speed up reactions? Many of these reactions require ATP to proceed because they need an input of energy to get started.","adbd4958-eb81-4783-ba9d-cdf5ca9a1312",[2761,2769,2780],{"id":2762,"data":2763,"type":67,"version":25,"maxContentLevel":34},"c43bca11-729d-4d02-890c-3701eac8d1b5",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2764,"multiChoiceCorrect":2766,"multiChoiceIncorrect":2767,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2765],"What process provides energy to recharge ADP?",[1998],[172,2647,2768],"Glycolysis",{"id":2770,"data":2771,"type":67,"version":24,"maxContentLevel":34},"3a016c50-731c-4193-92b6-4f4f98fcb0b2",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2772,"multiChoiceCorrect":2774,"multiChoiceIncorrect":2778,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2773],"What cellular function(s) does ATP provide energy for?",[2775,2776,341,2777],"Muscle contractions","DNA replication","Cell division",[2779],"Oxygen transport",{"id":2781,"data":2782,"type":67,"version":24,"maxContentLevel":34},"be51bba7-1202-44c7-8078-18fae5cdf063",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2783,"multiChoiceCorrect":2785,"multiChoiceIncorrect":2787,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2784],"Which of the following statements are true about enzymes?",[2786],"Proteins that speed up reactions",[2788,2789],"Proteins that slow down reactions","Proteins that are main reactants for chemical reactions",{"id":2791,"data":2792,"type":24,"maxContentLevel":34,"version":24,"reviews":2795},"8b52ff81-0e10-4079-bcfb-b78cfaac9c34",{"type":24,"markdownContent":2793,"audioMediaId":2794},"ATP is also crucial for **active transport** across cell membranes, which we touched on when discussing cell structure and function.\n\nActive transport is the process by which cells move substances against a concentration gradient, such as pumping nutrients into cells or expelling waste products.\n\n![Graph](image://f73ff4d1-f191-4d86-a29e-8a12ee276f3e \"Active Transport - Protein Pumps by Christinelmiller (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nThis process demands energy, which ATP provides.\n\nIn the broader context of metabolism, ATP acts as a bridge between the energy-producing catabolic reactions and the energy-consuming anabolic reactions.\n\nThis continuous cycle of breaking down molecules to produce ATP and then using that ATP to power the body’s functions is what keeps you alive and active. Whether it’s repairing a tissue, moving your muscles, or simply maintaining cellular function, ATP is at the heart of it all.","aa49e6a3-f2a2-4a9b-b07a-74753847ddd7",[2796],{"id":2797,"data":2798,"type":67,"version":24,"maxContentLevel":34},"326b5508-d147-431d-9d04-0baeabcb9db5",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2799,"multiChoiceCorrect":2801,"multiChoiceIncorrect":2804,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2800],"Which of the following statements are true about Active Transport?",[2802,2803],"Moves substances against a concentration gradient","Requires energy from ATP",[2805,2806,2807],"Moves substances along a concentration gradient","Does not require energy","Occurs only in plant cells",{"id":2809,"data":2810,"type":26,"maxContentLevel":34,"version":25,"orbs":2812},"682eecb2-edc5-4bc3-9e4f-396ee2a471da",{"type":26,"title":175,"tagline":2811},"The methods that stabilize the internal environments of organisms",[2813,2952],{"id":2814,"data":2815,"type":25,"version":25,"maxContentLevel":34,"summaryPage":2817,"introPage":2825,"pages":2831},"898026b1-2a39-4b20-a23e-39376025ad68",{"type":25,"title":2816},"Negative Feedback Loops",{"id":2818,"data":2819,"type":34,"maxContentLevel":34,"version":24},"a25c2195-ba16-4e1d-bfec-cea67be0f52a",{"type":34,"summary":2820},[2821,2822,2823,2824],"Negative feedback loops restore balance by counteracting changes.","Body temperature is regulated by negative feedback via the hypothalamus.","Insulin and glucagon maintain blood glucose through feedback loops.","ADH controls water balance by adjusting kidney function.",{"id":2826,"data":2827,"type":53,"maxContentLevel":34,"version":24},"79d80eef-2ba0-4204-87da-209819b7beb3",{"type":53,"intro":2828},[2829,2830],"How does your body cool down when it gets too hot?","What happens when your blood sugar gets too high?",[2832,2837,2864,2907],{"id":2833,"data":2834,"type":24,"maxContentLevel":34,"version":24},"bb82f4c4-9d22-4b12-a464-b89c633deb81",{"type":24,"markdownContent":2835,"audioMediaId":2836},"You’ve already learned about **homeostasis** earlier in the pathway: how organisms **maintain a stable internal environment** by regulating factors like pH, and temperature.\n\nAs we briefly touched upon, **homeostasis** works via feedback loops (both negative and positive). This orb is going to explore the former.\n\nNegative feedback loops are the mechanisms your body uses to maintain balance.\n\nThe term \"negative\" might sound counterintuitive because these loops are actually positive in the sense that they help keep your body stable.\n\nThe \"negative\" part refers to the process of counteracting or negating a change to bring things back to their normal state.\n\nEssentially, when a system in your body deviates from its normal range, a negative feedback loop works to correct that deviation and restore balance.","8b3be317-f36c-4911-8bc2-d648e6654c3d",{"id":2838,"data":2839,"type":24,"maxContentLevel":34,"version":24,"reviews":2842},"23c2df09-244a-45b6-b94e-3f0dc4a6dd63",{"type":24,"markdownContent":2840,"audioMediaId":2841},"To understand negative feedback loops, let’s revisit a familiar example—body temperature regulation.\n\nYou already know that your body needs to maintain a stable internal temperature to function properly.\n\nWhen your body detects that its temperature is rising, such as during exercise or on a hot day, a negative feedback loop is triggered.\n\n**Sensors** in your skin and brain detect the increase in temperature, and this information is sent to a control center in your brain called the **hypothalamus**.\n\nThe **hypothalamus** then initiates responses like sweating and vasodilation (widening of blood vessels) to cool the body down.\n\n![Graph](image://df97e584-d699-43c6-97ea-85299aa9f346 \"Sweating at Wilson Trail Stage One 1 by Minghong (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nAs your body cools, the temperature returns to its normal range and the responses (like sweating) decrease and eventually stop.\n\nThis is a classic negative feedback loop: the system responds to a change by acting in the **opposite direction** to restore balance.","7b8e9cbc-eadc-48ac-b962-4cc429c5a0d3",[2843,2852],{"id":2844,"data":2845,"type":67,"version":24,"maxContentLevel":34},"9cf958ea-5014-49f7-9e42-376f14a3eea7",{"type":67,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":2846,"binaryCorrect":2848,"binaryIncorrect":2850},[2847],"What is the primary function of negative feedback loops in the body?",[2849],"Counteracts changes",[2851],"Promotes changes",{"id":2853,"data":2854,"type":67,"version":24,"maxContentLevel":34},"ce4a02d4-170c-4fae-b0dc-8cbebe0acaa5",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2855,"multiChoiceCorrect":2857,"multiChoiceIncorrect":2860,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2856],"Which responses are initiated by the hypothalamus to cool the body?",[2858,2859],"Sweating","Vasodilation",[2861,2862,2863],"Shivering","Increased heart rate","Muscle contraction",{"id":2865,"data":2866,"type":24,"maxContentLevel":34,"version":25,"reviews":2869},"6591f15b-b3d0-400d-b259-459906b29b15",{"type":24,"markdownContent":2867,"audioMediaId":2868},"Another example is the regulation of **blood glucose levels**.\n\nAfter you eat, your blood glucose levels rise, which you’ve already learned is important because glucose provides energy for your cells. A negative feedback loop comes into play here as well.\n\nWhen the increase in glucose is detected, your **pancreas** releases **insulin**, which facilitates the uptake of glucose by your cells and reduces the glucose level in your blood.\n\n![Graph](image://1d268d3b-338c-4447-87c4-eaaa67ada91f \"Glucose Homeostasis. Image by Carogonz11 (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nAs glucose levels drop back to normal, insulin secretion decreases. This loop helps prevent your blood sugar from staying too high, which could be harmful.\n\nBut what happens if blood glucose levels drop too low?\n\nHere, another negative feedback loop kicks in. The pancreas releases glucagon, a hormone that triggers the release of stored glucose from the liver into the bloodstream, raising blood glucose levels back to normal.\n\nOnce balance is restored, glucagon secretion slows down. This back-and-forth regulation ensures that your body maintains a steady supply of glucose, preventing the dangerous extremes of too much or too little.","a2fea8d1-c895-4e2e-8794-f41a95ea594c",[2870,2884],{"id":883,"data":2871,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2872,"multiChoiceQuestion":2873,"multiChoiceCorrect":2875,"multiChoiceIncorrect":2877,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2880,"matchPairsPairs":2881},[880,884,885],[2874],"Which hormone is released by the pancreas to trigger glucose release from the liver?",[2876],"Glucagon",[1900,2878,2879],"ADH","Cortisol",[178],[2882],{"left":2876,"right":2883,"direction":34},"Triggers glucose release from liver",{"id":2885,"data":2886,"type":67,"version":25,"maxContentLevel":34},"56764b0c-ef1e-4968-9f9a-f202ef0ce3b6",{"type":67,"reviewType":15,"spacingBehaviour":24,"orderAxisType":128,"orderQuestion":2887,"orderItems":2888},[1235],[2889,2892,2895,2898,2901,2904],{"label":2890,"reveal":2891,"sortOrder":4},"Blood glucose levels rise after eating","1",{"label":2893,"reveal":2894,"sortOrder":24},"The pancreas releases insulin","2",{"label":2896,"reveal":2897,"sortOrder":25},"Blood glucose levels drop over time","3",{"label":2899,"reveal":2900,"sortOrder":34},"The pancreas releases glucagon","4",{"label":2902,"reveal":2903,"sortOrder":41},"Triggered by glucagon, the liver  releases stored glucose into the bloodstream","5",{"label":2905,"reveal":2906,"sortOrder":204},"Blood glucose levels finally return to normal","6",{"id":2908,"data":2909,"type":24,"maxContentLevel":34,"version":24,"reviews":2912},"a95cf136-7728-41b7-a089-a5b37509cbf5",{"type":24,"markdownContent":2910,"audioMediaId":2911},"**Water balance** in your body is also controlled by negative feedback loops.\n\nIf you’re dehydrated, sensors in your body detect the decrease in blood volume and concentration of solutes, signaling your brain to release antidiuretic hormone (ADH).\n\nADH prompts your kidneys to conserve water by reducing urine output, helping to restore your body’s water balance.\n\n![Graph](image://e07d744c-afd2-4a19-9be1-ffb10eca5292 \"Urine Hydration chart. Image by Petar Milošević (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nAs your hydration improves, the secretion of ADH decreases, again showing how the body uses these loops to maintain homeostasis.\n\nSo, while you already know about the importance of homeostasis in maintaining stability within cells, negative feedback loops are the specific mechanisms that your entire body uses to maintain this balance.\n\nThese loops work continuously to monitor and adjust physiological processes, ensuring that your internal environment remains within the narrow limits necessary for survival.","200ab8ac-2669-4173-936a-a774674985bf",[2913,2927,2937],{"id":2914,"data":2915,"type":67,"version":24,"maxContentLevel":34},"ea52a762-6750-4540-898b-6a91d2c74a13",{"type":67,"reviewType":15,"spacingBehaviour":24,"orderAxisType":128,"orderQuestion":2916,"orderItems":2918},[2917],"Put these stages of water balance regulation in order:",[2919,2921,2923,2925],{"label":2920,"reveal":2891,"sortOrder":4},"Dehydration detected by sensors (receptors)",{"label":2922,"reveal":2894,"sortOrder":24}," Brain releases antidiuretic hormone (ADH)",{"label":2924,"reveal":2897,"sortOrder":25}," ADH reduces urine output",{"label":2926,"reveal":2900,"sortOrder":34}," Body conserves water to maintain balance",{"id":2928,"data":2929,"type":67,"version":24,"maxContentLevel":34},"c619e8ba-ede4-4568-bcaf-86cb6fbb0454",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":2930,"multiChoiceCorrect":2932,"multiChoiceIncorrect":2936,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[2931],"Which of the following are examples of negative feedback loops?",[2933,2934,2935],"Body temperature regulation","Blood glucose regulation","Water balance regulation",[2777,341],{"id":884,"data":2938,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2939,"multiChoiceQuestion":2940,"multiChoiceCorrect":2942,"multiChoiceIncorrect":2944,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2948,"matchPairsPairs":2949},[880,883,885],[2941],"What is the function of Antidiuretic Hormone (ADH)?",[2943],"Reduces urine output",[2945,2946,2947],"Increases blood glucose","Decreases body temperature","Increases heart rate",[178],[2950],{"left":2951,"right":2943,"direction":34},"Antidiuretic Hormone",{"id":2953,"data":2954,"type":25,"version":24,"maxContentLevel":34,"summaryPage":2956,"introPage":2964,"pages":2970},"335c16e5-c581-4346-b789-1c93cb5c9192",{"type":25,"title":2955},"Positive Feedback Loops",{"id":2957,"data":2958,"type":34,"maxContentLevel":34,"version":24},"6ab33c41-1ca7-4590-bfed-e4ea5c3c19ca",{"type":34,"summary":2959},[2960,2961,2962,2963],"While negative feedback loops maintain stability, positive feedback loops push processes to completion","Childbirth uses positive feedback to intensify contractions until birth.","Blood clotting involves positive feedback to quickly seal wounds.","Nerve signals rely on positive feedback for rapid impulse generation.",{"id":2965,"data":2966,"type":53,"maxContentLevel":34,"version":24},"a605e95e-1ef5-4c0e-9e52-fafc9c108f2d",{"type":53,"intro":2967},[2968,2969],"How does oxytocin amplify contractions during childbirth?","What triggers the rapid accumulation of platelets in blood clotting?",[2971,2976,3009,3026],{"id":2972,"data":2973,"type":24,"maxContentLevel":34,"version":24},"31f75dd6-20a2-4594-84f1-f51882616c18",{"type":24,"markdownContent":2974,"audioMediaId":2975},"Having explored how negative feedback loops help maintain homeostasis by counteracting changes to keep your body’s internal environment stable, let’s now turn our attention to **positive feedback** loops.\n\nWhile negative feedback loops work to bring your body back to a set point, positive feedback loops do the opposite: they **amplify** a response, pushing the body further away from its normal state to achieve a specific outcome.\n\nPositive feedback loops are less common than negative ones, but they play crucial roles in certain physiological processes.","61436a3b-1ff7-46fc-ae46-4371762be09c",{"id":2977,"data":2978,"type":24,"maxContentLevel":34,"version":24,"reviews":2981},"3f59a925-4b8e-4806-a188-3419f58ba2ed",{"type":24,"markdownContent":2979,"audioMediaId":2980},"To understand positive feedback loops, it’s helpful to contrast them with what you’ve learned about negative feedback loops.\n\nIn a negative feedback loop, the body **detects a change and acts to reverse it,** thereby maintaining **stability**.\n\nIn a positive feedback loop, however, the response to a stimulus doesn’t stabilize the system but rather **intensifies it**. This amplification continues **until a specific event or outcome is reached**, at which point the loop is typically shut off.\n\nA classic example of a positive feedback loop in the body is the process of childbirth, which you can see in this diagram.\n\n![Graph](image://b2b263dc-2539-4c0e-895e-caf4d9e754f0 \"A positive feedback loop in the form of childbirth. Image: Hannah.gray05, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nAs labor begins, the baby’s head pushes against the cervix (1), which triggers a nerve impulse from the cervix to the brain (2). The brain then signals for the release of a hormone called oxytocin (3). Oxytocin causes the muscles of the uterus to contract, pushing the baby further down the birth canal (4).\n\nThese contractions then increase the pressure on the cervix, which leads to the release of even more oxytocin, intensifying the contractions. This loop continues, with contractions becoming stronger and more frequent until the baby is born.\n\nOnce the baby is delivered, the stimulus (pressure on the cervix) is removed, and the loop is terminated (5).\n\nIn this case, the positive feedback loop is crucial for driving the process to completion—ensuring that childbirth progresses efficiently.","01325a49-658f-43ee-b2d2-152fac089818",[2982,2995],{"id":885,"data":2983,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2984,"multiChoiceQuestion":2985,"multiChoiceCorrect":2987,"multiChoiceIncorrect":2989,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2990,"matchPairsPairs":2991},[880,883,884],[2986],"What hormone is released during childbirth that plays a crucial role in the positive feedback loop?",[2988],"Oxytocin",[958,1900,2876],[178],[2992],{"left":2993,"right":2994,"direction":34},"Oxytocin Hormone","Released during childbirth",{"id":1986,"data":2996,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":2997,"multiChoiceQuestion":2998,"multiChoiceCorrect":3000,"multiChoiceIncorrect":3002,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3006,"matchPairsPairs":3007},[1982,1985],[2999],"What is the primary function of positive feedback loops?",[3001],"Intensifies response to a stimulus until a specific outcome is reached",[3003,3004,3005],"Counteracts changes to maintain stability","Detects changes and acts to reverse them","Maintains homeostasis",[178],[3008],{"left":2955,"right":3001,"direction":34},{"id":3010,"data":3011,"type":24,"maxContentLevel":34,"version":24,"reviews":3014},"1c09bb34-f73c-4492-8630-7423a3ac8300",{"type":24,"markdownContent":3012,"audioMediaId":3013},"Another example of a positive feedback loop occurs during **blood clotting**.\n\nWhen a blood vessel is injured, platelets (small blood cells) adhere to the site of the injury and release chemicals that attract more platelets.\n\nThese additional platelets continue to accumulate, releasing more chemicals and attracting even more platelets.\n\nThis cascade effect accelerates rapidly, leading to the formation of a blood clot, which seals the wound and prevents further blood loss.\n\nHere, the positive feedback loop is essential for quickly responding to injury and ensuring that the clotting process is strong and effective enough to prevent excessive bleeding.\n\n![Graph](image://dd98717b-8b12-4ca7-8522-3eb2564f7b99 \"1909 Blood Clotting by OpenStax College (CC BY 3.0) \u003Chttps://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons\")","2374aeb0-8ea6-48ae-954e-7db2e5910a66",[3015],{"id":3016,"data":3017,"type":67,"version":24,"maxContentLevel":34},"c8427a38-c997-48a1-af26-03f9246328f9",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3018,"multiChoiceCorrect":3020,"multiChoiceIncorrect":3022,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3019],"What are platelets?",[3021],"Small blood cells involved in blood clotting",[3023,3024,3025],"Large white blood cells","Hormones released during stress","Proteins involved in muscle contraction",{"id":3027,"data":3028,"type":24,"maxContentLevel":34,"version":24,"reviews":3031},"c3579e81-3ae3-450c-9338-d1bb227aaab4",{"type":24,"markdownContent":3029,"audioMediaId":3030},"Positive feedback loops are also involved in the generation of **nerve signals**.\n\nWhen a nerve cell is stimulated, a small change in membrane potential occurs, causing sodium channels in the cell membrane to open.\n\nThis opening allows sodium ions to rush into the cell, which further depolarizes the membrane and causes more sodium channels to open. This process continues, leading to a rapid and significant change in membrane potential—a nerve impulse.\n\nOnce the impulse is generated, the loop is broken, and the cell resets to its resting state.\n\nIn this context, the positive feedback loop is crucial for ensuring that **nerve signals are strong and fast**, allowing for rapid communication within the nervous system.\n\nUnlike negative feedback loops, which are primarily concerned with maintaining stability and homeostasis, positive feedback loops are about pushing processes to completion. They’re like a chain reaction that, once started, needs to run its course to achieve a specific outcome.\n\nWhile these loops are powerful, they’re also tightly controlled and usually limited in scope because their unchecked amplification could potentially be harmful.","fb7f9b1f-033e-47df-be06-f09dd9ea3ecd",[3032,3043],{"id":3033,"data":3034,"type":67,"version":24,"maxContentLevel":34},"c92655d9-527a-4e2b-b86c-05ddfaf8cf96",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3035,"multiChoiceCorrect":3037,"multiChoiceIncorrect":3041,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[3036],"Which of the following are examples of positive feedback loops?",[3038,3039,3040],"Childbirth","Blood clotting","Generation of nerve signals",[3042,1063,1064],"Regulation of blood sugar",{"id":3044,"data":3045,"type":67,"version":24,"maxContentLevel":34},"e4b5fe74-1a11-433a-a9ee-6151311bc8ba",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3046,"multiChoiceCorrect":3048,"multiChoiceIncorrect":3052,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[3047],"Which of the following are characteristics of negative feedback loops?",[3049,3050,3051],"Counteract changes to maintain stability","Body detects a change and acts to reverse it","Primarily concerned with maintaining homeostasis",[3053,3054,3055],"Intensifies response to a stimulus","Tightly controlled and limited in scope","Amplifies changes",{"id":3057,"data":3058,"type":26,"maxContentLevel":34,"version":204,"orbs":3061},"f6491321-8d1c-4448-90a1-e67a558cfca7",{"type":26,"title":3059,"tagline":3060},"Gene Theory","How organisms pass on traits to the next generation",[3062,3177,3343,3500,3619],{"id":3063,"data":3064,"type":25,"version":34,"maxContentLevel":34,"summaryPage":3065,"introPage":3073,"pages":3079},"032253b8-a049-409a-a81f-d2607be795eb",{"type":25,"title":396},{"id":3066,"data":3067,"type":34,"maxContentLevel":34,"version":24},"74c8994d-5351-48e1-984c-d0bfe0b4774c",{"type":34,"summary":3068},[3069,3070,3071,3072],"DNA is life's blueprint, storing genetic instructions.","DNA's double helix structure ensures accurate replication.","Base pairs A-T and C-G maintain genetic code accuracy.","Mutations in DNA can drive evolution over time.",{"id":3074,"data":3075,"type":53,"maxContentLevel":34,"version":24},"ad1fce52-8413-42e8-b53b-2e1cfe28d9b4",{"type":53,"intro":3076},[3077,3078],"What shape does the DNA molecule take?","How do adenine and thymine pair up in DNA?",[3080,3105,3143,3160],{"id":3081,"data":3082,"type":24,"maxContentLevel":34,"version":24,"reviews":3085},"35204798-a95f-4187-94f7-686cf238d95c",{"type":24,"markdownContent":3083,"audioMediaId":3084},"As we continue exploring the fundamental concepts of biology, our focus now shifts to the mechanisms of heredity and how traits are passed down, building on our earlier exploration of cell structure and the role of DNA and RNA in encoding life’s information.\n\nIn this tile on Gene Theory, we'll first examine **DNA**: its structure, replication, and how mutations lead to genetic variation.\n\nDeoxyribonucleic acid (DNA) is the molecule that carries the genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms and many viruses.\n\n![Graph](image://c887d07f-a886-42bb-ac53-99a35c154ed7 \"DNA strands (CC0) \u003Chttp://creativecommons.org/publicdomain/zero/1.0/deed.en>, via Wikimedia Commons\")\n\nTo put it simply, DNA is like a set of instructions or a blueprint that tells an organism how to grow, develop, and function.\n\nDNA’s role in biology cannot be overstated; it is the chemical basis of heredity, guiding the biological processes that maintain life from one generation to the next.","a7ef8eaf-9b43-401a-9bc9-cf037ec716b5",[3086],{"id":3087,"data":3088,"type":67,"version":24,"maxContentLevel":34},"d89eeefd-0978-4e65-bd7e-561e1b9e9449",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":3089,"multiChoiceQuestion":3093,"multiChoiceCorrect":3095,"multiChoiceIncorrect":3097,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3101,"matchPairsPairs":3102},[3090,3091,3092],"7db446df-ddf1-4b7e-b6c1-57b1c2e52432","0b38c332-add5-41d1-8b99-9d259e815a20","6f2b2400-6ffa-41b7-b6d9-5e283eb65e40",[3094],"What is the mechanism of passing traits down generations called?",[3096],"Heredity",[3098,3099,3100],"Mutation","Replication","Transcription",[178],[3103],{"left":3096,"right":3104,"direction":34},"Mechanism of passing traits down generations",{"id":3106,"data":3107,"type":24,"maxContentLevel":34,"version":25,"reviews":3110},"945e6c46-d151-494b-8923-792efaeec816",{"type":24,"markdownContent":3108,"audioMediaId":3109},"The discovery of DNA as the hereditary material dates back to the mid-20th century, but its significance wasn’t fully understood right away.\n\nInitially, many scientists believed that proteins, not DNA, were responsible for heredity because proteins were more complex. However, as research progressed, it became clear that DNA played a crucial role in passing genetic information from one generation to the next.\n\nThe first step in understanding this came from the use of X-ray crystallography. In the early 1950s, **Rosalind Franklin**, working at King’s College London, captured critical images of DNA using this technique. Her most famous image, known as \"Photo 51,\" was taken in 1952 and provided crucial evidence that DNA had a **helical structure**.\n\n![Graph](image://e884b58e-4c9b-48d0-a982-420eda6879fd \"Rosalind Franklin by MRC Laboratory of Molecular Biology (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nThe story took a controversial turn when Maurice Wilkins, a colleague of Franklin’s at King’s College, shared her X-ray data with James Watson and Francis Crick without her knowledge or permission. **Watson and Crick**, who were working at the University of Cambridge, used Franklin’s data—combined with their own research—to build the first accurate model of the DNA double helix in 1953.\n\nWhile Watson, Crick, and Wilkins were awarded the Nobel Prize in Physiology or Medicine in 1962 for their discovery, Franklin’s contributions were largely overlooked. By the time the prize was awarded, Franklin had tragically died of ovarian cancer in 1958, at the age of 37.","8b9c5a49-d386-4e45-aa2c-86bcebf5f438",[3111,3126],{"id":1431,"data":3112,"type":67,"version":25,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":3113,"multiChoiceQuestion":3114,"multiChoiceCorrect":3116,"multiChoiceIncorrect":3118,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3122,"matchPairsPairs":3123},[1427,1430],[3115],"Who captured critical images of DNA using X-ray crystallography?",[3117],"Rosalind Franklin",[3119,3120,3121],"James Watson","Francis Crick","Maurice Wilkins",[178],[3124],{"left":3117,"right":3125,"direction":34},"Captured critical images of DNA using X-ray crystallography",{"id":3127,"data":3128,"type":67,"version":24,"maxContentLevel":34},"6916fd67-6494-4325-855c-165c28a74a02",{"type":67,"reviewType":15,"spacingBehaviour":24,"orderAxisType":24,"orderQuestion":3129,"orderItems":3130},[1235],[3131,3134,3137,3140],{"label":3132,"reveal":3133,"sortOrder":4},"Photo 51' taken by Rosalind Franklin","1952",{"label":3135,"reveal":3136,"sortOrder":24},"Watson and Crick built the first accurate DNA model","1953",{"label":3138,"reveal":3139,"sortOrder":25},"Rosalind Franklin dies","1958",{"label":3141,"reveal":3142,"sortOrder":34},"Watson, Crick, and Wilkins awarded the Nobel Prize","1962",{"id":3144,"data":3145,"type":24,"maxContentLevel":34,"version":24,"reviews":3148},"57d7d599-6d08-48db-bd6e-85a5dfb600ed",{"type":24,"markdownContent":3146,"audioMediaId":3147},"The **double helix** refers to the twisted ladder-like shape of the DNA molecule, where two long strands wind around each other.\n\nDNA is composed of two long strands forming a double helix, with each strand consisting of a sugar-phosphate backbone and nitrogenous bases (adenine, thymine, cytosine, and guanine) paired together through hydrogen bonds.\n\n![Graph](image://a717736e-2731-4728-9a31-56ae662aece6 \"DNA-structure-and-bases (Public domain), via Wikimedia Commons\")\n\nLet’s break that down:\n\nThe **sugar-phosphate backbone** is like the sides of the ladder, made up of alternating sugar (deoxyribose) and phosphate groups.\n\nThe nitrogenous bases (adenine, thymine, cytosine, and guanine) are like the rungs of the ladder. These bases pair up in a very specific way: **adenine** (A) pairs with **thymine** (T), and **cytosine** (C) pairs with **guanine** (G).\n\nThe specificity of these base pairings—adenine with thymine (A-T) and cytosine with guanine (C-G)— is crucial because it ensures that the genetic code is accurately copied during cell division.","24e5db68-ff55-4391-b7ee-dd5763484cec",[3149],{"id":3150,"data":3151,"type":67,"version":24,"maxContentLevel":34},"32f45f37-287c-46d5-b6e5-b6002e0523c8",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":3152,"matchPairsPairs":3154,"matchPairsShowExamples":6},[3153],"Match the base with its pair",[3155,3156,3157],{"left":2168,"right":2169,"direction":34},{"left":2170,"right":2171,"direction":34},{"left":3158,"right":3159,"direction":34},"Cyronine","Not a base",{"id":3161,"data":3162,"type":24,"maxContentLevel":34,"version":25,"reviews":3165},"7786b610-1333-4865-a23a-a846e123dacc",{"type":24,"markdownContent":3163,"audioMediaId":3164},"The discovery of the **double helix model** explained not only the structure of DNA and how it is stored but also how it could replicate itself, ensuring the faithful transmission of genetic information during cell division.\n\nWhen any cell prepares to divide (as it must for an organism to grow and develop), the DNA must make a copy.\n\nDuring replication, the DNA strands separate, and each strand serves as a template for the formation of a new complementary strand.\n\n![Graph](image://34c2582c-7f75-4296-883a-110341ab3d2b \"Nucleic acids - Transcription by Laboratoires Servier (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nThis semi-conservative replication ensures that each daughter cell receives an identical copy of the DNA, preserving the genetic information across generations.\n\n**\"Semi-conservative\"** means that each new DNA molecule has one old strand and one new strand, which helps maintain accuracy.\n\nErrors during the replication process, though rare, can lead to **mutations**—changes in the DNA sequence that may result in variations in the organism.\n\nMutations can be thought of as \"mistakes\" in the DNA code. Some mutations are neutral, some are harmful, and occasionally, a mutation may confer an advantage, contributing to evolution over time — a process we’ll come back to in the final tile.","1cc9ff71-8420-4574-896f-ba38f961f718",[3166],{"id":3167,"data":3168,"type":67,"version":24,"maxContentLevel":34},"08819116-3ed2-4cea-8117-6f7d8161870d",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3169,"multiChoiceCorrect":3171,"multiChoiceIncorrect":3173,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3170],"What does 'semi-conservative replication' mean?",[3172],"Each new DNA molecule has one old strand and one new strand",[3174,3175,3176],"Each new DNA molecule has two new strands","Each new DNA molecule has two old strands","Each new DNA molecule has one old strand and two new strands",{"id":3178,"data":3179,"type":25,"version":24,"maxContentLevel":34,"summaryPage":3181,"introPage":3189,"pages":3195},"f3dc47ea-ebad-49f1-a40b-58f187f67595",{"type":25,"title":3180},"Genes",{"id":3182,"data":3183,"type":34,"maxContentLevel":34,"version":24},"fa77ed84-d001-4a54-9165-d2eef1e2e9cb",{"type":34,"summary":3184},[3185,3186,3187,3188],"Genes are DNA segments coding for proteins.","Exons are coding regions; introns are non-coding.","Regulatory sequences control gene expression.","Mutations can alter traits or cause disorders.",{"id":3190,"data":3191,"type":53,"maxContentLevel":34,"version":24},"1a15bf4d-a76f-448b-b974-891fcee68fe6",{"type":53,"intro":3192},[3193,3194],"What do genes do in our bodies?","How do genes decide which proteins to make?",[3196,3231,3261,3299],{"id":3197,"data":3198,"type":24,"maxContentLevel":34,"version":24,"reviews":3201},"b4a77973-8954-48ac-a12d-4d48270e037f",{"type":24,"markdownContent":3199,"audioMediaId":3200},"Building upon our understanding of DNA, we now turn our attention to genes, the specific sequences of DNA that carry the instructions for building and maintaining an organism.\n\nA gene is a segment of DNA that contains the necessary information to produce a functional product, typically a protein.\n\nProteins, as we know, are important molecules that perform a wide range of functions in the body, from building tissues to regulating processes in cells.\n\nThe most common range for the length of a human gene is typically between 3,000 to 100,000 base pairs, though genes can vary greatly in size.\n\nSome genes are as short as a few hundred base pairs, while others can span millions of base pairs.","ecaa1acc-45fa-45cc-a65c-fe886975535f",[3202,3213,3221],{"id":3203,"data":3204,"type":67,"version":24,"maxContentLevel":34},"30edd417-ea2a-459c-91d3-e03dabad96a3",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3205,"multiChoiceCorrect":3207,"multiChoiceIncorrect":3209,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3206],"What is a gene?",[3208],"A segment of DNA with information to produce a functional product",[3210,3211,3212],"A segment of RNA with information to produce a functional product","A protein that regulates cell functions","A molecule that carries oxygen in the blood",{"id":3214,"data":3215,"type":67,"version":24,"maxContentLevel":34},"28e9bfc5-ff4b-4340-a1f4-da1ebe47b091",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3216,"multiChoiceCorrect":3218,"multiChoiceIncorrect":3219,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3217],"Genes are instructions typically used to produce which of the following?",[1763],[2364,1937,3220],"Vitamins",{"id":3222,"data":3223,"type":67,"version":24,"maxContentLevel":34},"616ff4ab-5823-4e9a-a1bc-109fca962aea",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3224,"multiChoiceCorrect":3226,"multiChoiceIncorrect":3228,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3225],"What is the common range of human gene lengths?",[3227],"3,000-100,000 base pairs",[3229,3230],"300-1000 base pairs","300,000-700,000 base pairs",{"id":3232,"data":3233,"type":24,"maxContentLevel":34,"version":24,"reviews":3236},"5a4603c6-53f0-444b-af10-619a934c538d",{"type":24,"markdownContent":3234,"audioMediaId":3235},"The structure of a gene is complex, encompassing more than just a straightforward sequence of **nucleotides**.\n\nA gene is partially made up of coding regions called **exons**, which contain the instructions for making proteins.\n\nThese **exons** are transcribed into RNA and ultimately translated into proteins, playing a direct role in determining the traits of an organism.\n\n![Graph](image://ba6630d3-ec2f-4bc3-b384-0e586fcfd8e6 \"Haploid human genome sequence by NHS National Genetics and Genomics Education Centre (CC BY 2.0) \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")\n\nIt's also important to note that despite the vast size of the human genome, only about 2% of our DNA actually codes for proteins. The remaining 98% includes non-coding regions, and some elements of these regions are still not fully understood.\n\nNon-coding regions of genes are known as ‘**introns**’, and they appear interspersed between exons.\n\nAlthough **introns** are transcribed into RNA, they are removed before the RNA is translated into a protein, and the exons are spliced together.\n\nThis splicing actually serves an important purpose, because this splicing of exons doesn’t always have to occur in the same way.\n\nDifferent combinations of exons can be spliced together in different ways, leading to the production of different proteins from the same gene.\n\nThis ability to create multiple proteins from a single gene significantly increases the variety of proteins your body can produce, which is important for the complexity and adaptability of living organisms​","7f2998ec-d822-4a9b-aeec-04256da36021",[3237,3248],{"id":3238,"data":3239,"type":67,"version":24,"maxContentLevel":34},"6751b030-30c3-4da6-a4e4-aaaffd9ca985",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":3240,"matchPairsPairs":3241,"matchPairsShowExamples":6},[178],[3242,3245],{"left":3243,"right":3244,"direction":34},"Exons","Coding regions of a gene",{"left":3246,"right":3247,"direction":34},"Introns","Non-coding regions of a gene",{"id":3249,"data":3250,"type":67,"version":24,"maxContentLevel":34},"97b2fd5e-26ad-453e-8155-d8e8d1f9001d",{"type":67,"reviewType":15,"spacingBehaviour":24,"orderAxisType":128,"orderQuestion":3251,"orderItems":3252},[1235],[3253,3255,3257,3259],{"label":3254,"reveal":2891,"sortOrder":4},"(Transcription) Exons and introns are transcribed from DNA into RNA",{"label":3256,"reveal":2894,"sortOrder":24},"(Intron removal) Introns are cut out of RNA molecule",{"label":3258,"reveal":2897,"sortOrder":25},"(Splicing) Remaining exons are spliced together to form continuous RNA sequence",{"label":3260,"reveal":2900,"sortOrder":34},"(Translation) Exons are translated into proteins",{"id":3262,"data":3263,"type":24,"maxContentLevel":34,"version":24,"reviews":3266},"37703f9e-4d41-4188-8f73-ce8bbcc56e1c",{"type":24,"markdownContent":3264,"audioMediaId":3265},"**Non-coding** regions of genes are not just \"junk DNA\": they include **regulatory** sequences that control the expression of these coding regions.\n\nBy ‘**gene expression**’, we mean the process by which the information in a gene is used to create a functional product, like a protein. We’ll come back to this in the following orb.\n\nThese regulatory sequences act like switches, determining when, where, and how much of a particular protein is produced.\n\n**Promoters**, **enhancers**, and **silencers** are specific DNA regulatory sequences that act as binding sites for proteins known as transcription factors. These transcription factors either promote or inhibit the transcription of the gene into RNA, depending on the needs of the cell.\n\n**Promoters** are like starting points, signaling where transcription should begin.\n\n**Enhancers** are sequences that boost the activity of promoters, increasing gene expression.\n\n**Silencers** do the opposite—they decrease gene expression.\n\nThis regulation ensures that genes are expressed at the right time and in the right cells, contributing to the proper development and function of an organism.","ef685e53-11ac-4c52-b713-062e889580bc",[3267,3284],{"id":3268,"data":3269,"type":67,"version":24,"maxContentLevel":34},"29c19352-97eb-44d7-8d09-bb322c4aeed0",{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":3270,"multiChoiceQuestion":3274,"multiChoiceCorrect":3276,"multiChoiceIncorrect":3278,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3279,"matchPairsPairs":3280},[3271,3272,3273],"361effe6-a09b-4fa4-afe4-5f2a3f873f4c","5f002250-6983-4e2c-b0ab-d59a85805d5b","7a59fe59-521a-4a47-bc5c-30bf2467fa1e",[3275],"What do regulatory gene sequences control?",[3277],"Gene expression",[341,2777,2776],[178],[3281],{"left":3282,"right":3283,"direction":34},"Regulatory gene sequences","Controls gene expression",{"id":3285,"data":3286,"type":67,"version":24,"maxContentLevel":34},"9f0f9166-dee7-4265-8cda-2d51c8d8cc1d",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":3287,"matchPairsPairs":3289,"matchPairsShowExamples":6},[3288],"Match the type of regulatory sequence to its effect:",[3290,3293,3296],{"left":3291,"right":3292,"direction":34},"Promoter","Acts as a starting point for transcription",{"left":3294,"right":3295,"direction":34},"Enhancer","Boosts activity of promoters and increases gene expression",{"left":3297,"right":3298,"direction":34},"Silencer","Decreases gene expression",{"id":3300,"data":3301,"type":24,"maxContentLevel":34,"version":24,"reviews":3304},"3c2fcd28-1c72-44ce-b5cd-fd74e07705f1",{"type":24,"markdownContent":3302,"audioMediaId":3303},"Genes are not isolated entities; they interact with each other and with various molecular pathways to influence an organism’s phenotype, the set of observable traits.\n\n**Phenotype** includes everything from eye color to blood type—traits that you can see or measure.\n\nThis interaction between genes and the environment also plays a crucial role in how traits are expressed.\n\nMutations in genes, whether spontaneous or induced by external factors, can lead to variations in these traits.\n\n![Graph](image://4120a6de-7c66-4ac8-885f-792584e8abc9 \"Darwin Hybrid Tulip Mutation 2014-05-01 by LepoRello (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nSome mutations may have no effect, others can lead to genetic disorders, and some might even confer advantages that contribute to evolutionary change. Genetic disorders are diseases or conditions caused by alterations in the DNA.","6c2de70b-6b5d-4c89-be9e-fb67b6a3ad15",[3305,3321,3332],{"id":3090,"data":3306,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":3307,"multiChoiceQuestion":3308,"multiChoiceCorrect":3310,"multiChoiceIncorrect":3312,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3316,"matchPairsPairs":3317},[3087,3091,3092],[3309],"What is a phenotype?",[3311],"The set of observable traits of an organism",[3313,3314,3315],"The genetic makeup of an organism","The process of gene expression","The sequence of DNA in a gene",[178],[3318],{"left":3319,"right":3320,"direction":34},"Phenotype","Set of observable traits of an organism",{"id":3322,"data":3323,"type":67,"version":24,"maxContentLevel":34},"81cc06d9-07b1-4027-8d44-b69a3e1c4794",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3324,"multiChoiceCorrect":3326,"multiChoiceIncorrect":3330,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[3325],"Which of the following influence an organism's phenotype?",[3327,3328,3329],"How different genes interact","How certain genes express themselves","Environmental factors (e.g. diet)",[3331],"Number of chromosomes",{"id":3333,"data":3334,"type":67,"version":24,"maxContentLevel":34},"15461b45-33c9-4ff7-b354-1c5fab8864db",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3335,"multiChoiceCorrect":3337,"multiChoiceIncorrect":3341,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[3336],"Which of the following are considered aspects of an organism's phenotype?",[3338,3339,3340],"Eye color and hair color","Blood type","Behavior",[3342],"Combination of genes",{"id":3344,"data":3345,"type":25,"version":24,"maxContentLevel":34,"summaryPage":3347,"introPage":3355,"pages":3361},"901c2cd0-f7d5-46e4-a419-1a8fbbf7945f",{"type":25,"title":3346},"Chromosomes",{"id":3348,"data":3349,"type":34,"maxContentLevel":34,"version":24},"60a14d61-37cd-4888-b517-ab4fc4e6ccb9",{"type":34,"summary":3350},[3351,3352,3353,3354],"Chromosomes are DNA-packed structures in the cell nucleus.","Humans have 23 chromosome pairs, inheriting one from each parent.","Genes have specific loci on chromosomes, aiding genetic mapping.","Telomeres and centromeres protect and organize chromosomes.",{"id":3356,"data":3357,"type":53,"maxContentLevel":34,"version":24},"8317da7e-d3aa-41cb-80d2-491ec4a83d0c",{"type":53,"intro":3358},[3359,3360],"What are chromosomes made of?","How do chromosomes ensure genetic diversity in offspring?",[3362,3379,3431,3459],{"id":3363,"data":3364,"type":24,"maxContentLevel":34,"version":24,"reviews":3367},"6625e8de-3d0d-4501-9bc6-0efc3f9717ed",{"type":24,"markdownContent":3365,"audioMediaId":3366},"Having explored the structure and function of genes, the next step in understanding how genetic information is organized and transmitted is to look at **chromosomes**.\n\n**Genes**, which carry the instructions for building and maintaining an organism, are not scattered randomly within the cell but are instead meticulously organized into structures called **chromosomes**. This organization ensures that the vast amount of genetic information in our cells is both compactly stored and efficiently accessible.\n\n![Graph](image://a0f79f03-b0ae-4c06-abe1-fed216275394 \"Pairs of human chromosomes. (Public domain), via Wikimedia Commons\")\n\nChromosomes are thread-like structures located in the nucleus of each cell, composed of tightly wound DNA.\n\nIf you think of genes as individual recipes in a vast cookbook, then chromosomes are like the chapters that organize these recipes into manageable sections.\n\nIn humans, the DNA contained within chromosomes is organized into **23 pairs**, totaling 46 chromosomes. Each chromosome within a pair is inherited from one parent, so you receive 23 chromosomes from your mother and 23 from your father.\n\nThis pairing ensures that offspring have a combination of genetic material from both parents, which is the foundation of biological diversity.","8b740a61-fed5-4bd0-a048-95ae47d9f50d",[3368],{"id":946,"data":3369,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":3370,"multiChoiceQuestion":3371,"multiChoiceCorrect":3373,"multiChoiceIncorrect":3374,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3375,"matchPairsPairs":3376},[941,944,945],[3372],"Where are chromosomes located within a cell?",[399],[391,379,2220],[178],[3377],{"left":3346,"right":3378,"direction":34},"Located in the nucleus of each cell",{"id":3380,"data":3381,"type":24,"maxContentLevel":34,"version":24,"reviews":3384},"93598476-19bf-475d-95c4-46cf4e287686",{"type":24,"markdownContent":3382,"audioMediaId":3383},"Each chromosome contains a long, continuous molecule of DNA, which is tightly coiled and condensed with the help of **histones**.\n\nThis compact structure allows the long DNA molecules to fit within the confined space of the cell nucleus. Think of it as packing a long, delicate piece of thread into a small spool to keep it organized and protected.\n\nThe DNA is wrapped around **histones** to form **nucleosomes**, which further coil and fold to create the compact structure of a chromosome.\n\n![Graph](image://1f09ebc7-a5a6-4339-b1ad-e856d14f3a12 \"Chromatin and histones (Public domain), via Wikimedia Commons\")","d0480cdc-c08b-4066-8101-ff59287790c6",[3385,3401,3413,3424],{"id":3271,"data":3386,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":3387,"multiChoiceQuestion":3388,"multiChoiceCorrect":3390,"multiChoiceIncorrect":3392,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3396,"matchPairsPairs":3397},[3268,3272,3273],[3389],"Which of the below applies to histones?",[3391],"They help in coiling and condensing DNA",[3393,3394,3395],"They assist in DNA replication","They break down DNA","They transport DNA out of the nucleus",[178],[3398],{"left":3399,"right":3400,"direction":34},"Histones","Proteins that package DNA by coiling and condensing it",{"id":3402,"data":3403,"type":67,"version":24,"maxContentLevel":34},"cc53ca1a-12de-4477-b182-d61b21e84caf",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":3404,"matchPairsPairs":3405,"matchPairsShowExamples":6},[178],[3406,3408,3411],{"left":3399,"right":3407,"direction":34},"Proteins DNA wraps around",{"left":3409,"right":3410,"direction":34}," Nucleosomes"," DNA wrapped around histones, basic unit of DNA packaging",{"left":3346,"right":3412,"direction":34}," Structures made of tightly coiled nucleosomes",{"id":3414,"data":3415,"type":67,"version":24,"maxContentLevel":34},"494cf0a6-f6aa-4082-97e7-71f37af097d6",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3416,"multiChoiceCorrect":3418,"multiChoiceIncorrect":3420,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3417],"How many pairs of chromosomes do humans have?",[3419],"23",[3421,3422,3423],"22","24","46",{"id":3425,"data":3426,"type":67,"version":24,"maxContentLevel":34},"6425a0c2-b838-48d7-ab82-e0f5ac0e378c",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3427,"multiChoiceCorrect":3429,"multiChoiceIncorrect":3430,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3428],"How many chromosomes does each parent contribute to their offspring?",[3419],[3421,3422,3423],{"id":3432,"data":3433,"type":24,"maxContentLevel":34,"version":24,"reviews":3436},"dff284af-a414-4368-8f70-2e307f4fb479",{"type":24,"markdownContent":3434,"audioMediaId":3435},"The genes on each chromosome are arranged in a specific order, and their position on a chromosome is referred to as a **locus**.\n\nThis order is consistent across individuals of the same species, which is why scientists can map genes to specific locations on specific chromosomes.\n\nFor example, if a gene responsible for a particular trait is located near the tip of chromosome 4, it will be found in the same place in every human.\n\nThis consistency allows scientists to precisely identify and study the genetic basis of various traits.\n\n![Graph](image://8f1da74f-563c-4a75-9e38-8f3606b983a2 \"Disease Gene Mapping with Multiple Chromosomes. Image by Esherma1 (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")","9880ce86-a76b-4af5-b4d1-be52f6b6c85f",[3437,3448],{"id":3438,"data":3439,"type":67,"version":24,"maxContentLevel":34},"8fd68b3e-40f4-48c3-927f-cf70a8fea23c",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3440,"multiChoiceCorrect":3442,"multiChoiceIncorrect":3446,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[3441],"What is consistent across individuals of the same species regarding chromosomes?",[3443,3444,3445],"Gene order","Chromosome length","Chromosome number",[3447],"Telomeres",{"id":3449,"data":3450,"type":67,"version":24,"maxContentLevel":34},"9e14604d-c126-4188-b37a-6f2556db0f60",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3451,"multiChoiceCorrect":3453,"multiChoiceIncorrect":3455,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3452],"What is the specific position of genes on a chromosome called?",[3454],"Locus",[3456,3457,3458],"Gene map","Locality","Gene cluster",{"id":3460,"data":3461,"type":24,"maxContentLevel":34,"version":24,"reviews":3464},"abf72237-3eb0-4465-ad03-3ea3d765a701",{"type":24,"markdownContent":3462,"audioMediaId":3463},"Chromosomes also contain regions that do not code for proteins but are essential for maintaining chromosome integrity and regulating gene expression.\n\n![Graph](image://097cc366-61e2-4a9c-9124-8313cc55696b \"Telomeres by AJC1 (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\n**Telomeres**, for instance (which you can see above), are repetitive sequences at the ends of chromosomes that protect them from degradation, much like the plastic tips on shoelaces prevent them from fraying.\n\n**Centromeres**, located near the center of chromosomes, are essential for the proper segregation of chromosomes during cell division, ensuring that each daughter cell receives the correct number of chromosomes.\n\nDuring **cell division**, chromosomes play a crucial role in ensuring that genetic information is accurately passed on to daughter cells.\n\nWhen a cell divides, its chromosomes are duplicated, and each new cell receives an identical set of chromosomes.\n\nDuring **mitosis**, this ensures that every cell in your body has the same genetic information.\n\nHowever, as you may remember from an earlier orb, in reproductive cells, a different type of cell division called **meiosis** occurs, reducing the chromosome number by half so that when fertilization happens, the resulting zygote has the correct number of chromosomes—restoring the full set of 46 in humans.","bb86dda8-dcd8-47e7-992d-4f8e9393ffaa",[3465,3477,3484],{"id":3466,"data":3467,"type":67,"version":24,"maxContentLevel":34},"45725716-2652-49c5-8217-60b9fc00facb",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":3468,"matchPairsPairs":3470,"matchPairsShowExamples":6},[3469],"Match the biological event to its consequences, in terms of chromosomes:",[3471,3474],{"left":3472,"right":3473,"direction":34},"Cell division (mitosis)","Chromosomes are duplicated to ensure identical genetic information",{"left":3475,"right":3476,"direction":34},"Fertilization"," Restores a full set of chromosomes (46 in humans) by the fusion of two haploid cells (sperm and egg, each with 23 chromosomes)",{"id":3478,"data":3479,"type":67,"version":24,"maxContentLevel":34},"f9b4500a-23e3-4b7a-ae13-5354aa2d8f74",{"type":67,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":3480,"activeRecallAnswers":3482},[3481],"What is the function of telomeres (the repetitive sequences at the ends of chromosomes)?",[3483],"Protect chromosomes from degradation (like the ends of a shoelace)",{"id":3272,"data":3485,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":3486,"multiChoiceQuestion":3487,"multiChoiceCorrect":3489,"multiChoiceIncorrect":3491,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3495,"matchPairsPairs":3496},[3268,3271,3273],[3488],"What role do centromeres (located near the center of chromosomes) play during cell division?",[3490],"Ensures the proper segregation of chromosomes",[3492,3493,3494],"Assist in DNA replication","Protect chromosome ends","Facilitate gene expression",[178],[3497],{"left":3498,"right":3499,"direction":34},"Centromeres","Middle chromosome sections essential for proper segregation in division",{"id":3501,"data":3502,"type":25,"version":41,"maxContentLevel":34,"summaryPage":3504,"introPage":3512,"pages":3518},"1a0e4eb2-c564-497a-9763-dac3cf9d8860",{"type":25,"title":3503},"Gene Expression",{"id":3505,"data":3506,"type":34,"maxContentLevel":34,"version":24},"aecf1591-4c11-4edd-9b20-3665fad8e59b",{"type":34,"summary":3507},[3508,3509,3510,3511],"DNA is a cookbook; genes are recipes.","mRNA carries DNA instructions to ribosomes.","Ribosomes translate mRNA into proteins.","Gene expression is tightly regulated and adaptable.",{"id":3513,"data":3514,"type":53,"maxContentLevel":34,"version":24},"c7da6d9b-489d-4e1b-9a4e-d05e78985120",{"type":53,"intro":3515},[3516,3517],"What are Mendel's laws of inheritance?","How do Mendel's laws explain trait transmission from parents to offspring?",[3519,3537,3556,3576,3589],{"id":3520,"data":3521,"type":24,"maxContentLevel":34,"version":34,"reviews":3524},"3c3c011c-7dc2-4bf3-9a10-21e920077529",{"type":24,"markdownContent":3522,"audioMediaId":3523},"**Gene expression** is the process by which the information encoded in DNA is used to produce the observable traits of an organism.\n\nThis concept is central to understanding how the instructions in our genes are translated into the proteins that perform almost every function in the body.\n\nTo grasp gene expression, we need to start with the central dogma of molecular biology, which outlines the flow of genetic information from DNA to RNA to protein.\n\nThe process begins with transcription, where the **DNA sequence of a gene is copied into messenger RNA (mRNA).**\n\n![Graph](image://fbdd9aec-178b-42f8-9435-ad0efa4c4f4b \"TranscriptionGraphic PublicDomain (CC0) \u003Chttp://creativecommons.org/publicdomain/zero/1.0/deed.en>, via Wikimedia Commons\")","afddabe2-3a2b-4560-9c4c-11e97f80316b",[3525],{"id":804,"data":3526,"type":67,"version":34,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":3527,"multiChoiceQuestion":3528,"multiChoiceCorrect":3530,"multiChoiceIncorrect":3531,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3533,"matchPairsPairs":3534},[801,805],[3529],"What is the process by which DNA information leads to observable traits?",[3503],[3100,3532,3099],"Translation",[178],[3535],{"left":3503,"right":3536,"direction":34},"Process by which DNA information produces observable traits",{"id":3538,"data":3539,"type":24,"maxContentLevel":34,"version":24,"reviews":3542},"a48e63ba-517f-4425-b52e-83e5ea0b1854",{"type":24,"markdownContent":3540,"audioMediaId":3541},"Imagine DNA as a large cookbook, and each gene as a specific recipe within it.\n\n**Transcription** is like copying one of these recipes onto a separate sheet of paper—this sheet is the mRNA, which will carry the instructions out of the DNA “cookbook” and into the cell’s kitchen.\\\n\\\n**Transcription** is initiated when an enzyme called **RNA polymerase** binds to a specific region of the DNA, known as the promoter, which signals the start of the gene.\n\n**RNA polymerase** unwinds the DNA helix and creates a complementary strand of mRNA by matching RNA nucleotides to the DNA template.\n\n![Graph](image://c8f713a4-6965-43b6-ab48-93f908ab5427 \"Image: Genomics Education Programme, CC BY 2.0 \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")\n\nUnlike DNA, where adenine (A) pairs with thymine (T), in RNA, adenine pairs with uracil (U).\n\nThis newly formed mRNA strand is like a portable recipe, ready to be used outside the nucleus of the cell.","f43c879b-adb0-4b39-a47c-5f140e780042",[3543],{"id":3544,"data":3545,"type":67,"version":24,"maxContentLevel":34},"d9389d7a-037a-4cf5-a04b-20bd3e9b0e97",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3546,"multiChoiceCorrect":3548,"multiChoiceIncorrect":3552,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[3547],"Which three actions are performed by RNA Polymerase during transcription?",[3549,3550,3551],"Binds to promoter to initiate transcription (step 1)","Unwinds DNA helix (step 2)","Creates complementary mRNA strand (step 3)",[3553,3554,3555],"Splices RNA (step 2)","Translates mRNA (step 2)","Adds amino acids to protein chain (step 3)",{"id":3557,"data":3558,"type":24,"maxContentLevel":34,"version":25,"reviews":3561},"1ed32f81-cadf-4fd3-95be-af8670e34524",{"type":24,"markdownContent":3559,"audioMediaId":3560},"After transcription, once the mRNA is synthesized, it undergoes **processing**. This involves removing **introns**—non-coding sections of RNA—and splicing together **exons**, the coding regions that will be used to build the protein.\n\n![Graph](image://ff400c8d-f1f1-4ecb-8227-80e95384a618 \"DNA exons and introns splicing process. Image (Public domain), via Wikimedia Commons\")\n\nThe processed mRNA then exits the nucleus and enters the cytoplasm, where it meets the cell's **ribosomes**.\n\nThink of ribosomes as chefs in the cell’s kitchen, responsible for reading the mRNA \"recipe\" and assembling the protein.\n\nIn the **translation** stage, the ribosome reads the mRNA sequence and translates it into a chain of **amino acids**, the building blocks of proteins.","e0849fce-6587-4a8e-8dc0-3e8a46be79f0",[3562],{"id":3563,"data":3564,"type":67,"version":24,"maxContentLevel":34},"a6273a13-62ed-44b4-90ec-48294b4b7d34",{"type":67,"reviewType":15,"spacingBehaviour":24,"orderAxisType":128,"orderQuestion":3565,"orderItems":3567},[3566],"What happens after transcription, once the mRNA is synthesized?",[3568,3570,3572,3574],{"label":3569,"reveal":2891,"sortOrder":4},"mRNA undergoes processing (removing introns and splicing together exons)",{"label":3571,"reveal":2894,"sortOrder":24},"mRNA exits the nucleus and enters cytoplasm",{"label":3573,"reveal":2897,"sortOrder":25},"mRNA encounters ribosomes",{"label":3575,"reveal":2900,"sortOrder":34},"Ribosomes 'translate' mRNA sequence into amino acids",{"id":3577,"data":3578,"type":24,"maxContentLevel":34,"version":24,"reviews":3581},"7fdc8e59-8be0-4a13-963e-d4e9c1db453b",{"type":24,"markdownContent":3579,"audioMediaId":3580},"During **translation**, transfer RNA (tRNA) molecules bring the appropriate amino acids to the ribosome, where they are linked together in a particular order.\n\nThe **Transfer RNA** (tRNA) molecules know the correct order in which to bring amino acids to the ribosome because they follow the sequence of codons in the mRNA.\n\n![Graph](image://2c1750c3-690b-43a5-88cd-eb11a0398229 \"Transcription and translation. Image: NHS National Genetics and Genomics Education Centre, CC BY 2.0 \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")\n\n**Codons** are groups of three nucleotides in the mRNA that specify which amino acid should be added next.\n\nThe growing chain of amino acids eventually folds into a functional protein, ready to carry out its role in the cell.","e97c2516-dbd6-4a39-892b-28a8dea4f3af",[3582],{"id":3583,"data":3584,"type":67,"version":24,"maxContentLevel":34},"153e1f3f-0781-44ca-8cbb-74a67454a79a",{"type":67,"reviewType":41,"spacingBehaviour":24,"clozeQuestion":3585,"clozeWords":3587},[3586],"Transfer RNA (tRNA) molecules bring the appropriate amino acids to the ribosome, where they are linked together in a particular order.",[3588],"amino acids",{"id":3590,"data":3591,"type":24,"maxContentLevel":34,"version":24,"reviews":3594},"317e1419-c678-491c-ac2d-fd7f65660cee",{"type":24,"markdownContent":3592,"audioMediaId":3593},"**Gene expression** is one-way directed process, though not a simple one; it is carefully regulated at multiple stages to ensure that proteins are produced at the right time, in the right place, and in the right amounts.\n\nAdditionally, other mechanisms like regulatory RNAs and epigenetic modifications can fine-tune the expression of genes in response to the cell’s needs or environmental changes.\n\n**Epigenetic modifications** involve changes that affect gene expression without altering the DNA sequence itself. A common example is the addition of a chemical group called a methyl group to DNA, which can turn a gene off or reduce its activity.\n\n![Graph](image://01b6b043-348d-4e99-97c5-663c832b0b67 \"Epigenetic mechanisms (Public domain), via Wikimedia Commons\")\n\nFor example, in response to chronic stress, **methyl groups** may be added to genes involved in stress regulation, lowering their activity. This could be the body's way of adapting to prolonged stress by lessening the impact of stress hormones.\n\nThis tightly regulated process of gene expression is also the foundation of many modern biotechnologies, such as genetic engineering and gene therapy, which aim to manipulate gene expression to treat genetic disorders by restoring the proper levels of key proteins.","279e2a7f-1e65-4426-948c-fbbb415856d2",[3595,3609],{"id":3596,"data":3597,"type":67,"version":24,"maxContentLevel":34},"1935280b-4ad2-4d56-9da4-fd7e3747d2c9",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3598,"multiChoiceCorrect":3600,"multiChoiceIncorrect":3604,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[3599],"Which of the following apply to the concept of epigenetic modification?",[3601,3602,3603],"Changes affecting gene expression without altering the DNA sequence","Example: addition of chemical groups like methyl groups to DNA","Can turn genes off or reduce their activity",[3605,3606,3607,3608],"Changes in DNA sequence","Direct protein synthesis","RNA splicing","Example: insertion of a mutation in the DNA sequence",{"id":3610,"data":3611,"type":67,"version":24,"maxContentLevel":34},"c2e10806-0202-4d7a-b912-291dafe600e5",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":3612,"matchPairsPairs":3614,"matchPairsShowExamples":6},[3613],"Match the gene expression process to its description:",[3615,3617],{"left":3100,"right":3616,"direction":34},"DNA is copied into mRNA in the nucleus.",{"left":3532,"right":3618,"direction":34},"mRNA is decoded to assemble proteins in the ribosome",{"id":3620,"data":3621,"type":25,"version":24,"maxContentLevel":34,"summaryPage":3622,"introPage":3630,"pages":3636},"bac2070a-c8a6-435a-abca-b794f31d325e",{"type":25,"title":3096},{"id":3623,"data":3624,"type":34,"maxContentLevel":34,"version":24},"47c8c166-715a-489f-b6cc-783c6bbc1ec8",{"type":34,"summary":3625},[3626,3627,3628,3629],"Genes are organized into pairs called alleles.","Dominant alleles mask recessive ones in traits.","Alleles separate during gamete formation, restoring pairs in offspring.","Traits are inherited independently, following Mendel's laws.",{"id":3631,"data":3632,"type":53,"maxContentLevel":34,"version":24},"18a99d82-6673-4014-a65a-58e302bd414d",{"type":53,"intro":3633},[3634,3635],"How do dominant alleles affect an organism's traits?","What role do alleles play in determining phenotype?",[3637,3654,3691,3729],{"id":3638,"data":3639,"type":24,"maxContentLevel":34,"version":24,"reviews":3642},"2569ebed-20d8-4a51-977e-00d975519daf",{"type":24,"markdownContent":3640,"audioMediaId":3641},"With a solid understanding of how genes are organized into chromosomes and how they function within cells, we can now explore how these genes are passed from one generation to the next—a process known as **heredity**.\n\nHeredity is the mechanism by which genetic information is transmitted from parents to offspring, ensuring the continuity of life and the preservation of traits within a species.\n\nThe foundational principles of heredity were first uncovered by **Gregor Mendel**, a 19th-century scientist often referred to as the \"father of modern genetics.\"\n\n![Graph](image://c936a398-f78c-43cf-973a-da6657216bb6 \"Gregor Mendel (Public domain), via Wikimedia Commons\")\n\n**Mendel** discovered these patterns through meticulous experiments with pea plants, Mendel discovered that traits are inherited in specific, predictable patterns, governed by what we now understand to be genes.\n\n![Graph](image://d6b8eb67-9a35-4191-8080-86b82ddc6fad \"Doperwt rijserwt peulen Pisum sativum by Rasbak (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")\n\nThese **laws of heredity** laid the groundwork for modern genetics by establishing the idea that genes are the fundamental units of inheritance, passed from parents to offspring in a predictable manner.\n\nThe discovery of chromosomes as the carriers of genes later confirmed and expanded on Mendel’s principles, integrating them into the broader framework of molecular biology.","de63142f-c57c-4e20-9735-d44ce2796695",[3643],{"id":3644,"data":3645,"type":67,"version":24,"maxContentLevel":34},"b86bd8fb-6b89-42f4-868c-0b5b82e5a88e",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3646,"multiChoiceCorrect":3648,"multiChoiceIncorrect":3650,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3647],"What did Gregor Mendel use in his experiments to discover the principles of heredity?",[3649],"Pea plants",[3651,3652,3653],"Fruit flies","Corn plants","Mice",{"id":3655,"data":3656,"type":24,"maxContentLevel":34,"version":24,"reviews":3659},"8e88392d-7705-433b-b55e-2b130cd9fbb8",{"type":24,"markdownContent":3657,"audioMediaId":3658},"One of Mendel’s key discoveries was the concept that **genes exist in pairs**, with each parent contributing one 'version' of that gene to their offspring. These pairs of genes are known as alleles, and they can be either **dominant** or **recessive**.\n\nThis principle is known as Mendel’s **Third Law of Dominance**.\n\nA **dominant allele** is like the louder voice in a pair—it tends to express itself in the organism’s traits, even if the other allele (from the other parent) is different.\n\nFor instance, if the allele for **purple flower** color is **dominant**, a pea plant with one purple flower allele and one white flower allele will still have purple flowers because the dominant purple allele \"masks\" the presence of the recessive white allele.\n\n![Graph](image://2a58dca5-8ff6-402c-8d30-1ad3f04d72fe \"Pisum sativum biflorum1 (Public domain), via Wikimedia Commons\")\n\nA **recessive allele** is quieter and will only express itself in the organism’s traits if both alleles for that trait are recessive.\n\nIn our example, the white flower color would only appear if the pea plant inherited the white allele from both parents. But if it appeared alongside a dominant purple the white allele would remain hidden, but could still be passed on to the next generation.\n\nSo, if a pea plant carries one allele for purple flowers (dominant) and one for white flowers (recessive), the dominant purple allele will determine the flower color, while the white allele remains hidden but can still be passed on to the next generation.","f82fa619-a345-4e95-8d02-e94fd5155302",[3660,3675],{"id":3273,"data":3661,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":3662,"multiChoiceQuestion":3663,"multiChoiceCorrect":3665,"multiChoiceIncorrect":3667,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3671,"matchPairsPairs":3672},[3268,3271,3272],[3664],"What are alleles?",[3666],"Versions of genes contributed by each parent",[3668,3669,3670],"Single genes inherited from one parent","Proteins that determine traits","Chromosomes that carry genetic information",[178],[3673],{"left":3674,"right":3666,"direction":34},"Alleles",{"id":3091,"data":3676,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":3677,"multiChoiceQuestion":3678,"multiChoiceCorrect":3680,"multiChoiceIncorrect":3682,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3686,"matchPairsPairs":3687},[3087,3090,3092],[3679],"When does a recessive allele express itself in an organism's traits?",[3681],"Only if both alleles for that trait are recessive",[3683,3684,3685],"When it is paired with a dominant allele","When it is inherited from the mother","When it is inherited from the father",[178],[3688],{"left":3689,"right":3690,"direction":34},"Recessive Allele","Expresses traits only when present in two copies",{"id":3692,"data":3693,"type":24,"maxContentLevel":34,"version":24,"reviews":3696},"600c723e-1e49-49ce-ad52-4abdaa85458d",{"type":24,"markdownContent":3694,"audioMediaId":3695},"Mendel’s first law, **the Law of Segregation**, explains how these alleles are separated during the formation of gametes—sperm and egg cells—so that each gamete carries only one allele for each trait.\n\nWhen fertilization occurs, the offspring inherits one allele from each parent, restoring the pair.\n\n![Graph](image://f9f29b34-32ad-47d2-ab3b-76da6a380795 \"Sperm-egg (Public domain), via Wikimedia Commons\")\n\nAnother key principle Mendel discovered is the **Law of Independent Assortment**, which explains how different traits are inherited independently of one another.\n\nThis law states that the **alleles for different traits** segregate independently during the formation of gametes.\n\nAs a result, the inheritance of one trait (such as flower color) does not influence the inheritance of another (such as seed shape).\n\nThis principle applies primarily to genes located on different chromosomes or far apart on the same chromosome.\n\nMendel’s experiments showed that when crossing plants with two different traits, the offspring exhibited combinations of traits in ratios that could be mathematically predicted, demonstrating the independent nature of allele assortment.","255d221f-5cf9-439a-9191-916508b4e10e",[3697,3708,3719],{"id":3698,"data":3699,"type":67,"version":24,"maxContentLevel":34},"214216aa-960c-4775-ac6c-33715dbdd341",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3700,"multiChoiceCorrect":3702,"multiChoiceIncorrect":3704,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3701],"What does the Law of Segregation explain?",[3703],"The separation of alleles during gamete formation",[3705,3706,3707],"The dominance of certain alleles","The independent assortment of traits","The inheritance of linked genes",{"id":3709,"data":3710,"type":67,"version":24,"maxContentLevel":34},"d0d2429b-2eee-4bf9-8a71-cae9b711ce56",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3711,"multiChoiceCorrect":3713,"multiChoiceIncorrect":3715,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3712],"What do gametes carry, in terms of alleles?",[3714],"One allele for each trait",[3716,3717,3718],"Two alleles for each trait","Only dominant alleles","Only recessive alleles",{"id":3720,"data":3721,"type":67,"version":24,"maxContentLevel":34},"476a99d1-b015-4fee-82d5-04317c316e04",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3722,"multiChoiceCorrect":3724,"multiChoiceIncorrect":3726,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3723],"Mendel's Law of Independent Assortment states that alleles for different traits segregate independently. What does this mean for heredity?",[3725],"Offspring can inherit different combinations of traits from each parent",[3727,3728],"Groups of traits are inherited in specific bundles from one parent","Traits are inherited randomly, with no rules governing how they are inherited",{"id":3730,"data":3731,"type":24,"maxContentLevel":34,"version":24,"reviews":3734},"db075717-c5f4-4043-b65a-acd05e14a02f",{"type":24,"markdownContent":3732,"audioMediaId":3733},"\nAs well as introducing the concept of dominant and recessive traits, Mendel’s work laid the foundation for the concepts of **genotype** and **phenotype**.\n\nThe **genotype** refers to the genetic makeup of an organism—the specific combination of alleles it possesses.\n\nThe **phenotype** is the observable expression of these traits—what we can actually see, such as eye color or height.\n\n![Graph](image://3da0b941-010c-4139-9ac8-065324b204da \"Coquina variation in phenotype. Image by Debivort (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")\n\nWhile the genotype determines the potential for a trait, the phenotype can be influenced by interactions between different alleles, as well as environmental factors.\n\nFor example, even if someone has the genetic potential for tall stature (genotype), factors like nutrition during growth years can influence the actual height (phenotype).\n\nThe principles of Mendel’s laws apply universally to all sexually reproducing organisms, from plants to animals to humans.\n\nThey form the basis for understanding not only simple inheritance patterns but also more complex phenomena such as genetic disorders, polygenic traits (traits controlled by multiple genes), and the role of genetic variation in evolution.\n\nHeredity is the engine of **evolution**—and this will be the topic of our final orb.","de129801-5e4d-4469-8dd4-97c5ecde6156",[3735,3746],{"id":3736,"data":3737,"type":67,"version":24,"maxContentLevel":34},"365d4143-2626-441b-8db5-a3c994cfe8d1",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3738,"multiChoiceCorrect":3740,"multiChoiceIncorrect":3742,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3739],"What influences the phenotype of an organism?",[3741],"Genotype and environmental factors",[3743,3744,3745],"Only genotype","Only environmental factors","Neither genotype nor environmental factors",{"id":3092,"data":3747,"type":67,"version":24,"maxContentLevel":34},{"type":67,"reviewType":34,"spacingBehaviour":24,"collapsingSiblings":3748,"multiChoiceQuestion":3749,"multiChoiceCorrect":3751,"multiChoiceIncorrect":3753,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":3756,"matchPairsPairs":3757},[3087,3090,3091],[3750],"What are polygenic traits?",[3752],"Traits controlled by multiple genes",[3754,3755],"Traits influenced by the environment","Traits that are always dominant",[178],[3758],{"left":3759,"right":3752,"direction":34},"Polygenic Traits",{"id":3761,"data":3762,"type":26,"maxContentLevel":34,"version":25,"orbs":3765},"44c3221a-0502-466c-8473-5478e7b85dc3",{"type":26,"title":3763,"tagline":3764},"Evolution","How natural selection fuels adaptation and speciation",[3766,3888,4024,4082,4173,4354],{"id":3767,"data":3768,"type":25,"version":24,"maxContentLevel":34,"summaryPage":3769,"introPage":3777,"pages":3783},"853fd38a-bed5-4282-9222-eba5e95fae8c",{"type":25,"title":817},{"id":3770,"data":3771,"type":34,"maxContentLevel":34,"version":24},"e625cfe3-d2e5-40e8-abaf-faca6e1f5467",{"type":34,"summary":3772},[3773,3774,3775,3776],"Darwin's finches had different beaks on each island.","Traits like beak shape help survival in specific environments.","Advantageous traits become common through survival and reproduction.","Natural selection drives species evolution over time.",{"id":3778,"data":3779,"type":53,"maxContentLevel":34,"version":24},"574d00b9-c448-426a-a0d6-61d97350c53f",{"type":53,"intro":3780},[3781,3782],"How do genetic variations lead to different traits in a population?","How does inheritance play a role in the diversity of traits?",[3784,3811,3828,3847,3863],{"id":3785,"data":3786,"type":24,"maxContentLevel":34,"version":24,"reviews":3789},"0ad2c9fc-fa79-4bd0-aded-e5c1913261b4",{"type":24,"markdownContent":3787,"audioMediaId":3788},"In 1831, a 22-year-old Englishman named **Charles Darwin** embarked on a voyage that would change the course of science.\n\n![Graph](image://4a20d035-5f6b-4a92-b6b8-85a77821f1fa \"Hw-darwin (Public domain), via Wikimedia Commons\")\n\nAboard the HMS Beagle, Darwin was hired as a naturalist to survey the coasts of South America. The purpose of the expedition was to chart the coastline and collect specimens that could help in understanding the natural world.\n\nFour years after the journey began, the Beagle reached the Galápagos Islands: a remote archipelago located about 1,000 kilometers off the coast of Ecuador.\n\n![Graph](image://68d6c1d8-82ba-42cd-904a-2bd6cfee161b \"Galápagos Islands ESA23188644 (Attribution), via Wikimedia Commons\")\n\nThe islands held an array of unique animals and plants that immediately fascinated Darwin.\n\nOver the course of five weeks, he observed the islands' unusual inhabitants, meticulously collecting and documenting specimens.","adeaea98-0c3f-40ed-ae96-cb6e35a64f56",[3790,3801],{"id":3791,"data":3792,"type":67,"version":24,"maxContentLevel":34},"5d641273-4a4c-473e-9cd4-7eb3cd87c7c9",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3793,"multiChoiceCorrect":3795,"multiChoiceIncorrect":3797,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3794],"What was the original purpose of Darwin's voyage aboard the HMS Beagle?",[3796],"To chart the coastline and collect specimens",[3798,3799,3800],"To find new trade routes","To establish a British colony","To investigate genes",{"id":3802,"data":3803,"type":67,"version":24,"maxContentLevel":34},"78c4d3ed-cc64-42ae-9a9e-219548f0f736",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3804,"multiChoiceCorrect":3806,"multiChoiceIncorrect":3808,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3805],"In what year did Darwin embark on his voyage aboard the HMS Beagle?",[3807],"1831",[1233,3809,3810],"1800","1901",{"id":3812,"data":3813,"type":24,"maxContentLevel":34,"version":24,"reviews":3816},"d7e35473-022a-4ea6-a85d-f1088f947d72",{"type":24,"markdownContent":3814,"audioMediaId":3815},"As Darwin moved from island to island, he noticed that many of the species were similar, yet subtly different.\n\nFor instance, he observed that **finches** on each island had distinct beak shapes and sizes. Some finches had long, narrow beaks ideal for picking insects out of tree bark, while others had short, thick beaks designed for cracking seeds.\n\n![Graph](image://2600df08-568d-4e99-9b37-d972cc7cb518 \"Darwin's finches by Gould (Public domain), via Wikimedia Commons\")\n\nWhy did the finches on each island have different beak shapes?\n\nWhat could explain the variation in the shells of the **giant tortoises**, which seemed to vary depending on the island they inhabited? On one island, tortoises had dome-shaped shells, while on another, they had saddleback shells, allowing them to stretch their necks higher to reach vegetation.\n\n![Graph](image://0ca74e15-bdbf-4431-aeae-814bb403551a \"El Chato Reserve Galápagos tortoise (Chelonoidis nigra) black and white photograph by David Adam Kess (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nSimilarly, the **mockingbirds** on one island differed in subtle ways from those on another. Why did mockingbirds on one island differ from those on another?\n\nThese observations led Darwin to wonder: could these differences have something to do with the environment of each island?","010328b1-7e84-47b1-83e1-3a52d6cc24ff",[3817],{"id":3818,"data":3819,"type":67,"version":24,"maxContentLevel":34},"961afb27-3022-431f-8a27-19ebe1d84a88",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3820,"multiChoiceCorrect":3822,"multiChoiceIncorrect":3824,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3821],"Which country are the Galápagos Islands closest to?",[3823],"Ecuador",[3825,3826,3827],"Brazil","Canada","Australia",{"id":3829,"data":3830,"type":24,"maxContentLevel":34,"version":24,"reviews":3833},"cee24707-6df0-40f8-8481-6cf0d342e4af",{"type":24,"markdownContent":3831,"audioMediaId":3832},"Upon his return to England, Darwin studied his findings with even greater detail.\n\nHe found that the birds he thought were just varieties of finches were **actually** **different species**, each uniquely adapted to its specific island environment.\n\nThe mockingbirds and tortoises followed a similar pattern.\n\nAt that time, the prevailing view in Europe was that species were immutable, meaning they were unchanging and had been created in their current form by a divine creator.\n\n![Graph](image://d3477b0d-cf5d-4286-a0a5-d7be082dce9a \"The Creation of Adam (Public domain), via Wikimedia Commons\")\n\nThis concept was rooted in the belief that every species had been designed for a specific purpose and that they had remained the same since their creation.\n\nHowever, Darwin's observations in the Galápagos challenged this long-held belief.","48ef3f71-52d0-4dbf-9bb1-9823e3f37fdb",[3834],{"id":3835,"data":3836,"type":67,"version":24,"maxContentLevel":34},"d81a043d-fde4-4267-94ff-ec456fdb376d",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3837,"multiChoiceCorrect":3839,"multiChoiceIncorrect":3843,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[3838],"Which specimens did Darwin collect during his voyage?",[3840,3841,3842],"Finches","Tortoises","Mockingbirds",[3844,3845,3846],"Penguins","Kangaroos","Polar bears",{"id":3848,"data":3849,"type":24,"maxContentLevel":34,"version":24,"reviews":3852},"04679429-f7b6-47df-987b-4fe54d2c3303",{"type":24,"markdownContent":3850,"audioMediaId":3851},"Darwin began to theorize that certain traits, like the beak shapes of finches or the shell forms of tortoises, might give some individuals an advantage in survival and reproduction, particularly in the challenging environments of the Galápagos Islands.\n\nFor example, a finch with a beak well-suited for cracking seeds might be **more likely to survive** in an environment where seeds are the primary food source.\n\n![Graph](image://5c9baae7-3c9a-484f-b1f9-2b976f500ce9 \"Evolution sm (Public domain), via Wikimedia Commons\")\n\nOver time, these advantageous traits would become more common in the population, because those individuals with favorable traits were the ones to survive long enough to reproduce.\n\nIn other words, the individuals of that species ‘fittest’ to survive in a given environment were the ones most likely to pass those traits on to the next generation. This process is often called “**survival of the fittest**”.\n\nOver long periods, “survival of the fittest” can lead to the development of new species as populations with different advantageous traits become distinct from each other.\n\nThis process, Darwin theorized, was a key mechanism behind the changes in species over time and would later become known as the **theory of natural selection**.","93c68d0a-dfef-4390-99ec-afa8833cd986",[3853],{"id":3854,"data":3855,"type":67,"version":24,"maxContentLevel":34},"957ca94a-c084-4b16-88bd-f31ca7ccfa41",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3856,"multiChoiceCorrect":3858,"multiChoiceIncorrect":3860,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3857],"What is a consequence of natural selection over time?",[3859],"Gradual development of new species",[3861,3862],"Gradual extinction of all species","Gradual uniformity of species",{"id":3864,"data":3865,"type":24,"maxContentLevel":34,"version":24,"reviews":3868},"71ded8ea-5030-4606-a10c-23a31d568fbd",{"type":24,"markdownContent":3866,"audioMediaId":3867},"In 1859, more than two decades after his visit to the Galápagos, Darwin published his ideas in the seminal work ***On the Origin of Species***.\n\n![Graph](image://85a4ce20-50d7-45da-9557-90420b3aa5d3 \"Origin of Species (Public domain), via Wikimedia Commons\")\n\nThe theory he proposed—natural selection—suggested that species evolve over time through the gradual accumulation of small, inherited changes that increase an organism's chances of survival and reproduction.\n\nThe rest of the tile will focus on how Darwin’s **theory of evolution** actually works. For instance, how do traits like beak shape or shell form get inherited?\n\nWhy do these variations arise in the first place?\n\nHow do populations of the same species diverge over time to become entirely new species?\n\nTogether, these sections form a comprehensive picture of evolution, a process that has shaped the diversity of life on Earth and continues to influence the living world today.","5f881018-856f-4afb-8ab8-789c43228351",[3869,3877],{"id":3870,"data":3871,"type":67,"version":24,"maxContentLevel":34},"fce4a9c5-f7da-4cb2-8449-6ecfeacf0459",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3872,"multiChoiceCorrect":3874,"multiChoiceIncorrect":3875,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3873],"In what year was 'On the Origin of Species' published?",[1233],[3807,3876,1510],"1900",{"id":3878,"data":3879,"type":67,"version":24,"maxContentLevel":34},"f3b11ac8-b2f7-490e-9ca3-b890afa23e61",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3880,"multiChoiceCorrect":3882,"multiChoiceIncorrect":3884,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3881],"What was the consequence of the publication of 'On the Origin of Species'?",[3883],"Increasing acceptance of the theory of natural selection",[3885,3886,3887],"Increasing rejection of evolutionary theory","Immediate controversy and ban","Recognition of Darwin as a religious leader",{"id":3889,"data":3890,"type":25,"version":24,"maxContentLevel":34,"summaryPage":3892,"introPage":3900,"pages":3906},"ea2c4668-4aaf-4865-a58c-4359cdfba210",{"type":25,"title":3891},"Genetic Variation",{"id":3893,"data":3894,"type":34,"maxContentLevel":34,"version":24},"8ca4972f-e3e7-493e-b5e4-f031ac0105ba",{"type":34,"summary":3895},[3896,3897,3898,3899],"Mutations drive genetic variation in isolated populations.","Genetic drift impacts small populations through random allele changes.","Gene flow introduces new genes, boosting genetic diversity.","Hidden traits emerge under environmental stress, aiding survival.",{"id":3901,"data":3902,"type":53,"maxContentLevel":34,"version":24},"512253a8-61bb-445d-906c-2aec72ba9ea0",{"type":53,"intro":3903},[3904,3905],"How does genetic variation lead to competition for resources?","Why do mutations matter in isolated populations?",[3907,3931,3968,4007],{"id":3908,"data":3909,"type":24,"maxContentLevel":34,"version":24,"reviews":3912},"73a45755-2857-44b0-91a5-bd68b8f5cf3b",{"type":24,"markdownContent":3910,"audioMediaId":3911},"The observations Darwin made in the Galápagos Islands—such as the differing beak shapes of finches and the varied shell forms of tortoises—led him to question how such variations could arise and persist in **isolated populations**.\n\nGenetic variation is the differences in DNA sequences that exist within a population. Even in small populations, genetic variation can be surprisingly high. But how is genetic variation actually generated, maintained, and expressed? This orb will examine this question more closely.\n\nFirst, let's take a look at **mutations**, a key driver of genetic variation.\n\n**Mutations** occur when there are errors in DNA replication or due to external factors like UV radiation or chemicals. Even in small populations, such as those on isolated islands, mutations occur continuously.\n\n![Graph](image://8533c4d8-716f-4b36-a1da-5ee987e1c734 \"Effect of a mutation (13080960754) by Genomics Education Programme (CC BY 2.0) \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")\n\nWhile most mutations are neutral or deleterious, a small fraction can be beneficial. For instance, in a population of pocket mice living on lava flows in the American Southwest, a single mutation in the Mc1r gene caused **darker fur**, giving these mice better camouflage against the dark volcanic rock.\n\n![Graph](image://db5162d7-0974-4702-9aeb-185e6fce352f \"Great Basin pocket mouse. Image: Mt Carmel rock shop. (38184650445) by Dr Mary Gillham Archive Project (CC BY 2.0) \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")\n\nOver time, this mutation spread through the population, despite its small size, highlighting how even isolated groups can harbor significant genetic diversity.\n\nThis principle could explain how certain traits in Galápagos species, like the finches' beak shapes, might have arisen in response to their specific environments.","652c70e7-60d3-41b9-a292-981d3f807898",[3913,3924],{"id":3914,"data":3915,"type":67,"version":24,"maxContentLevel":34},"cfa220f9-c101-48c3-beaa-91514027e42f",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3916,"multiChoiceCorrect":3918,"multiChoiceIncorrect":3920,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3917],"What did Darwin observe in the Galápagos Islands that led him to question how variations arise and persist in isolated populations?",[3919],"Finch beak shapes and tortoise shell forms",[3921,3922,3923],"Color variations in lizards","Size differences in iguanas","Feather patterns in birds",{"id":3925,"data":3926,"type":67,"version":24,"maxContentLevel":34},"14cf4e86-22ee-47b6-8622-671f9a963676",{"type":67,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":3927,"activeRecallAnswers":3929},[3928],"What are mutations?",[3930],"Errors in DNA sequence due to abnormal replication or external factors",{"id":3932,"data":3933,"type":24,"maxContentLevel":34,"version":24,"reviews":3936},"86e90c4a-1bdd-4da7-8659-d04e07451cba",{"type":24,"markdownContent":3934,"audioMediaId":3935},"Genetic drift is another critical mechanism, especially in small populations like those on the Galápagos Islands. Genetic drift refers to random fluctuations in allele frequencies due to chance events. In small populations, these random changes can have outsized effects.\n\n![Graph](image://5686b3af-ac2d-4896-abe0-5d66aa384742 \"Illustration of genetic drift. Image (Public domain), via Wikimedia Commons\")\n\nTake, for example, what’s known as a **population bottleneck**: a sudden reduction in population size, often due to events like natural disasters or disease, drastically reduces the number of individuals.\n\nThese kinds of events lead to a loss of genetic diversity.\n\nThe **cheetah** population experienced such a bottleneck thousands of years ago, reducing its genetic diversity. Despite this, cheetahs have managed to survive and even thrive, though with consequences like increased susceptibility to disease due to reduced genetic variation.\n\n![Graph](image://867a25ca-1def-42d5-bcda-9a1c5f68cfb7 \"Cheetah. Image by schani (CC BY-SA 2.0) \u003Chttps://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons\")","3992b9c5-8bd1-4999-844f-da03a127e593",[3937,3946,3957],{"id":3938,"data":3939,"type":67,"version":24,"maxContentLevel":34},"a0dd2b61-0200-475c-bdff-0ee56cfe9243",{"type":67,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":3940,"binaryCorrect":3942,"binaryIncorrect":3944},[3941],"What can cause a population bottleneck?",[3943],"Natural disasters or disease",[3945],"Increased food supply",{"id":3947,"data":3948,"type":67,"version":24,"maxContentLevel":34},"631cca11-361e-4bd2-87e7-83b8a3ee3531",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3949,"multiChoiceCorrect":3951,"multiChoiceIncorrect":3953,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3950],"What was the consequence of the population bottleneck experienced by cheetahs?",[3952],"Reduced genetic diversity",[3954,3955,3956],"Increased population size","Improved hunting skills","Enhanced resistance to cold",{"id":3958,"data":3959,"type":67,"version":24,"maxContentLevel":34},"0698f7c6-5e49-43b8-aa9c-3774bd71ce9d",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3960,"multiChoiceCorrect":3962,"multiChoiceIncorrect":3964,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3961],"What is genetic drift?",[3963],"Random fluctuations in allele frequencies due to chance events",[3965,3966,3967],"Directed evolution","Change in allele frequencies due to natural selection","Change in allele frequencies due to gene flow",{"id":3969,"data":3970,"type":24,"maxContentLevel":34,"version":24,"reviews":3973},"347b04e2-14b7-4acf-9fcf-9cc91bdd7f00",{"type":24,"markdownContent":3971,"audioMediaId":3972},"**Gene flow**—the movement of genes between populations—also plays a pivotal role in maintaining genetic diversity. In small, isolated populations, gene flow can introduce new genetic material, preventing the loss of variation that might otherwise occur due to genetic drift or inbreeding.\n\n![Graph](image://06356e3b-c170-426d-ab75-51ec8c5da3ef \"Gene flow Figure 19 02 04 by OpenStax, Rice University (CC BY 4.0) \u003Chttps://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons\")\n\nFor example, when a **single wolf** from the mainland crossed the ice bridge to Isle Royale, it introduced new alleles into the small wolf population there, which had been suffering from inbreeding depression.\n\nInbreeding depression occurs when closely related individuals breed, leading to an increased chance of harmful genetic traits being expressed, which can reduce the population's overall fitness.\n\nTherefore, the single event of a wolf crossing from the mainland eventually significantly boosted the genetic diversity of the entire population of the wolves in Isle Royale, demonstrating how even minimal gene flow can have a substantial impact.","15166b92-89b1-4a76-9150-c5e5b1f0b1ff",[3974,3985,3996],{"id":3975,"data":3976,"type":67,"version":24,"maxContentLevel":34},"2340bff8-bdd2-4768-98ad-6a7a5be97700",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3977,"multiChoiceCorrect":3979,"multiChoiceIncorrect":3981,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3978],"A lone wolf crossed the ice bridge to Isle Royale and introduced new alleles into its small population. What problem did this help to solve?",[3980],"Inbreeding depression",[3982,3983,3984],"Overpopulation","Genetic drift","Gene flow",{"id":3986,"data":3987,"type":67,"version":24,"maxContentLevel":34},"3de34e37-3e73-4fd2-a29c-f008d2b37066",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3988,"multiChoiceCorrect":3990,"multiChoiceIncorrect":3992,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[3989],"What is the effect of inbreeding depression?",[3991],"Increases chance of harmful genetic traits being expressed",[3993,3994,3995],"Enhances genetic diversity","Improves survival rates","Increases population size",{"id":3997,"data":3998,"type":67,"version":24,"maxContentLevel":34},"6f90a4db-1017-461d-b8fe-4fd44cfbb773",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":3999,"multiChoiceCorrect":4001,"multiChoiceIncorrect":4003,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4000],"What is gene flow?",[4002],"Movement of genes between populations",[4004,4005,4006],"Loss of genetic material","Increase in population size","Adaptation to environment",{"id":4008,"data":4009,"type":24,"maxContentLevel":34,"version":24,"reviews":4012},"1476369d-8904-47f8-b264-22c18f40af8c",{"type":24,"markdownContent":4010,"audioMediaId":4011},"There are other mechanisms that also contribute to maintaining genetic diversity, that we’ll look at a little more closely in our later orb on ‘adaptation’.\n\nThese include **balanced polymorphism**, which helps maintain certain genetic traits when they offer advantages in different conditions.\n\nA well-known example is the sickle cell trait in humans. In regions where malaria is common, individuals with one copy of the sickle cell gene have a survival advantage because they are more resistant to **malaria**.\n\n![Graph](image://cf91ac23-dfb3-47df-b257-519fb2cbbc5c \"Sickle cell 01 (Public domain), via Wikimedia Commons\")\n\n**Epistasis** involves complex interactions between genes, influencing traits in ways that aren't always obvious from individual genes alone.\n\nAnd finally, **hidden genetic variation** refers to genetic traits that remain unnoticed until changes in the environment reveal them. For instance, certain plants might carry genetic variants that do not affect their growth under normal conditions but become advantageous under drought stress.","64e07f39-fc53-4f0d-90b0-87e630bab772",[4013],{"id":4014,"data":4015,"type":67,"version":24,"maxContentLevel":34},"6477d121-5fd2-48f3-b991-5e699ade456c",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4016,"multiChoiceCorrect":4018,"multiChoiceIncorrect":4020,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[4017],"Which of the following is an example of balanced polymorphism?",[4019],"Sickle cell trait in humans reducing susceptibility to malaria",[4021,4022,4023],"Dominance of brown eye color in humans","Albinism","Mutations causing Down syndrome",{"id":4025,"data":4026,"type":25,"version":24,"maxContentLevel":34,"summaryPage":4028,"introPage":4036,"pages":4042},"629a2149-9494-4868-95c6-0408923b687a",{"type":25,"title":4027},"Overproduction",{"id":4029,"data":4030,"type":34,"maxContentLevel":34,"version":24},"d9404533-f8ce-474f-a184-8835c674dfbe",{"type":34,"summary":4031},[4032,4033,4034,4035],"Overproduction ensures some offspring survive despite high mortality rates.","Limited resources mean only the fittest offspring survive to adulthood.","Advantageous traits help organisms survive and reproduce in scarcity.","Genetic variation boosts survival chances in changing environments.",{"id":4037,"data":4038,"type":53,"maxContentLevel":34,"version":24},"16b7deac-f44e-43bf-ab12-24189f8d4d32",{"type":53,"intro":4039},[4040,4041],"Why do some finches survive better than others on the Galápagos Islands?","How does overproduction help sea turtles adapt to their environment?",[4043,4060,4065],{"id":4044,"data":4045,"type":24,"maxContentLevel":34,"version":24,"reviews":4048},"dce351a1-c101-428a-b139-c2258759f48a",{"type":24,"markdownContent":4046,"audioMediaId":4047},"The questions Darwin pondered during his time in the Galápagos Islands—such as why so many organisms produced far more offspring than could possibly survive—touch upon a fundamental aspect of evolutionary biology: overproduction.\n\n**Overproduction** of organisms refers to the tendency of living organisms to produce more offspring than their environment can support.\n\n![Graph](image://4e44e612-c6ba-448e-8b14-2f9147657ed7 \"Fish eggs. Image: Roe Ameiurus nebulosus by Alter welt (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nThis is observed across a wide range of species, from plants and insects to birds and mammals.\n\nThe sheer number of offspring ensures that, even in the face of high mortality rates, some will survive to adulthood and reproduce.\n\nAnd this phenomenon plays a critical role in the process of natural selection.","9e8e22d3-dc80-41cf-9691-57006360c45f",[4049],{"id":4050,"data":4051,"type":67,"version":24,"maxContentLevel":34},"b91ea323-bf56-42b2-b3ab-480939ac214d",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4052,"multiChoiceCorrect":4054,"multiChoiceIncorrect":4056,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4053],"Which of the below refers to the concept of 'overproduction' in evolutionary biology?",[4055],"Organisms produce more offspring than their environment can support",[4057,4058,4059],"Organisms produce fewer offspring than their environment can support","Organisms produce offspring only during specific seasons","Organisms produce offspring that are all guaranteed to survive",{"id":4061,"data":4062,"type":24,"maxContentLevel":34,"version":24},"ee929a55-94c9-451e-a198-e2e25bcc9608",{"type":24,"markdownContent":4063,"audioMediaId":4064},"Consider the finches of the Galápagos Islands that Darwin observed.\n\nEach finch might lay multiple eggs, resulting in many chicks. However, the islands' resources—such as food and nesting sites—are limited.\n\nNot all of these chicks will survive to maturity. Some will die due to predation, disease, or simply because they cannot compete successfully for food.\n\nThose that do survive are typically the ones best suited to their environment. For example, a finch with a beak shape that allows it to efficiently access food sources will have a better chance of surviving during times of scarcity.\n\n![Graph](image://c92cddc9-3ee1-43dc-a8f3-fcc40f96bad2 \"Darwin's finches by Gould (Public domain), via Wikimedia Commons\")\n\nThese advantageous traits, which can arise from genetic variation and mutations, are then passed on to the next generation.","82249008-8f3b-478d-b559-7aa64f78a428",{"id":4066,"data":4067,"type":24,"maxContentLevel":34,"version":24,"reviews":4070},"0c2e7a7f-512b-474c-9e6b-814405eb70cd",{"type":24,"markdownContent":4068,"audioMediaId":4069},"An example of overproduction can be seen in sea turtles.\n\n![Graph](image://54518360-d645-4615-a29f-ca9b944c57ee \"Hawaii turtle 2 by Brocken Inaglory (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")\n\nA single female sea turtle may lay hundreds of eggs in one nesting season. For instance, a loggerhead sea turtle may lay around 100-126 eggs per clutch and can nest several times a season. However, the survival rate from egg to adulthood is very low. Typically, only about 1 in 1,000 to 1 in 10,000 hatchlings survive to reach maturity.\n\n![Graph](image://565371fc-913a-4ba3-9af2-efb4e219eeb6 \"Newly hatched common snapping turtles emerging from the ground by Treggetrebor (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nThe high mortality rate among sea turtle hatchlings is due to predators, environmental hazards, and competition.\n\nThose few that survive are often the ones with traits that give them a slight edge, whether it’s a stronger shell, faster swimming speed, or better camouflage.\n\n**Overproduction** actually **amplifies the effects of genetic variation** within a population.\n\nWith more individuals, there is a greater chance for different genetic combinations to be expressed. This increases the likelihood that some individuals will possess advantageous traits, which can then be selected for through the pressures of natural selection.\n\nThis process is particularly important in dynamic environments where conditions may change rapidly, as it allows populations to adapt to new challenges.","271a75e0-1bdc-4eea-bbd9-c8533d9cff4e",[4071],{"id":4072,"data":4073,"type":67,"version":24,"maxContentLevel":34},"e4c4713b-199b-4cb8-94ef-ce4a8e746dc2",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4074,"multiChoiceCorrect":4076,"multiChoiceIncorrect":4078,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4075],"Why does overproduction increase the probability of beneficial traits?",[4077],"More individuals mean more genetic variation and traits",[4079,4080,4081],"All offspring directly inherit beneficial traits from parents","Overproduction reduces environmental hazards for all hatchlings","Only strong individuals survive, creating uniform traits",{"id":4083,"data":4084,"type":25,"version":24,"maxContentLevel":34,"summaryPage":4085,"introPage":4093,"pages":4099},"88168324-5975-4d9c-99af-3df7da3ea3bb",{"type":25,"title":773},{"id":4086,"data":4087,"type":34,"maxContentLevel":34,"version":24},"5acd3f49-7619-4546-a29d-6a1cc0f7c62a",{"type":34,"summary":4088},[4089,4090,4091,4092],"Mutations can lead to antibiotic resistance in bacteria.","Hidden genetic variation helps yeast adapt to stress.","Gene flow spreads adaptive traits in wolves and sticklebacks.","Epistasis allows maize to adapt to different climates.",{"id":4094,"data":4095,"type":53,"maxContentLevel":34,"version":24},"8bc3986d-b683-4cc3-aa40-ec28e7402ee6",{"type":53,"intro":4096},[4097,4098],"How do mutations help bacteria survive antibiotics?","What role does gene flow play in stickleback fish adaptation?",[4100,4125,4130,4158],{"id":4101,"data":4102,"type":24,"maxContentLevel":34,"version":24,"reviews":4105},"062ee438-3ad3-4ac6-9982-9f2c1b66cd9d",{"type":24,"markdownContent":4103,"audioMediaId":4104},"**Adaptation**, a key mechanism in evolution, is the process by which organisms become **better suited to their environments.**\n\nHaving earlier explored the sources of variation—such as mutation, genetic drift, hidden variation, and gene flow—it's important to now examine **how these mechanisms drive and contribute to specific adaptations in different organisms.**\n\nIn this section, we'll look more closely at this through several examples, from animals to simpler organisms like bacteria and plants.\n\nMutations, as we've discussed, are changes in the DNA sequence that can lead to new traits. While most mutations are neutral or harmful, those that confer an advantage in a particular environment can become the basis for adaptation.\n\nA prime example of **adaptation driven by mutation** is seen in **bacteria, particularly in the context of antibiotic resistance**. When a population of bacteria is exposed to an antibiotic, most of the bacteria are killed, but those with mutations that confer resistance survive and reproduce.\n\n![Graph](image://2bff031b-fb33-4e8d-b10a-fe575bb7d1f3 \"Antibiotic sensitivity and resistance by Dr Graham Beards (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nIn plants, mutations can also lead to important adaptations. The development of C4 photosynthesis in certain plants is an adaptation to hot, arid environments.\n\nOver time, plants with these mutations, rather than the standard C3 photosynthesis, thrived in dry climates where water was scarce, leading to the spread of C4 photosynthesis in species like maize and sugarcane.","337ed536-be53-4e61-b835-7fa92de23285",[4106,4114],{"id":4107,"data":4108,"type":67,"version":24,"maxContentLevel":34},"9cc02fb8-a592-42d3-8793-9734eb72ba92",{"type":67,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":4109,"binaryCorrect":4111,"binaryIncorrect":4112},[4110],"What is the process by which organisms become better suited to their environments?",[773],[4113],"Gene Flow",{"id":4115,"data":4116,"type":67,"version":24,"maxContentLevel":34},"f56a61eb-0076-401d-8271-f5cd358ef9e8",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4117,"multiChoiceCorrect":4119,"multiChoiceIncorrect":4121,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4118],"What is the consequence of antibiotic resistance in bacteria?",[4120],"Bacteria with resistance mutations survive and reproduce",[4122,4123,4124],"Bacteria become more susceptible to antibiotics","Bacteria stop reproducing","Bacteria lose their resistance over time",{"id":4126,"data":4127,"type":24,"maxContentLevel":34,"version":24},"91341d3b-f9d1-4cd9-aa27-20afd3102166",{"type":24,"markdownContent":4128,"audioMediaId":4129},"**Hidden genetic variation**, which we touched on briefly in our orb on ‘genetic variation’, refers to genetic differences that do not manifest in the phenotype unless triggered by specific environmental conditions. This hidden variation can become a reservoir of potential adaptations, ready to be revealed when the environment changes.\n\nA classic example of hidden variation contributing to adaptation can be seen in yeast populations.\n\n![Graph](image://5a5e8bb0-efd7-45cc-9223-fc6d2e75a67e \"Yeast cells (CC BY 4.0) \u003Chttps://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons\")\n\nYeast cells carry many genetic variants that do not affect their phenotype under normal conditions.\n\nHowever, when exposed to environmental stressors—such as changes in temperature or pH—some of these hidden variants become advantageous.\n\nFor instance, in **acidic environments**, certain yeast strains express previously silent genes that help them survive in low pH conditions. This ability to tap into hidden variation allows yeast populations to quickly adapt to fluctuating environments.","c977ec33-45e6-4769-b8dc-453b87bacfa5",{"id":4131,"data":4132,"type":24,"maxContentLevel":34,"version":24,"reviews":4135},"ff425909-ed0a-4634-aedc-8be0c05e9f15",{"type":24,"markdownContent":4133,"audioMediaId":4134},"**Gene flow**, as we saw in the example of the Isle Royale wolf, is the movement of genes between populations. It plays a crucial role in spreading adaptive traits across populations and maintaining genetic diversity, which can enhance a species' ability to adapt to new challenges.\n\nAnother striking example of **gene flow facilitating adaptation** is seen in the i**nterbreeding between wild and domesticated species.**\n\nIn the case of wolves and domestic dogs, gene flow has led to the exchange of adaptive traits. For instance, in regions where wolves and dogs coexist, wolves have occasionally acquired traits such as increased disease resistance or behavioral adaptations through gene flow from dogs. This exchange of genes can enhance the wolves' ability to survive in environments where they face new challenges, such as exposure to human-related diseases or changes in prey availability.\n\n![Graph](image://7a6ab61a-08dc-4dc0-ae55-8ba6143b3e38 \"Above, a jackall, a fox, a wolf and two dogs; below, a bulld (CC BY 4.0) \u003Chttps://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons\")\n\nIn aquatic environments, gene flow between populations of the threespine stickleback fish has led to the spread of adaptive traits that enable these fish to survive in both marine and freshwater environments.\n\nWhen marine sticklebacks colonized freshwater habitats, gene flow allowed the exchange of traits such as reduced armor plating, which is advantageous in the absence of marine predators.\n\nThis adaptation has enabled sticklebacks to thrive in diverse aquatic environments, demonstrating how gene flow can drive adaptation in response to different ecological pressures.","a5753e73-7c93-4df7-bc37-f89a2ce22513",[4136,4147],{"id":4137,"data":4138,"type":67,"version":24,"maxContentLevel":34},"6904a3f9-0db5-4317-ba33-52fc859139ee",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4139,"multiChoiceCorrect":4141,"multiChoiceIncorrect":4143,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[4140],"Which of the following statements describe or apply to Gene Flow?",[4002,4142],"Maintains genetic diversity and spreads adaptive traits",[4144,4145,4146],"Reduces genetic variation between populations","Occurs only during reproduction within a single population","Causes genes to mutate within a population",{"id":4148,"data":4149,"type":67,"version":24,"maxContentLevel":34},"092cad2b-8c7a-4c8e-8e24-32cd06d7c8d9",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4150,"multiChoiceCorrect":4152,"multiChoiceIncorrect":4154,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4151],"What is the consequence of gene flow in wolves and dogs?",[4153],"Exchange of adaptive traits like disease resistance",[4155,4156,4157],"Wolves become domesticated","Dogs become wild","No exchange of traits occurs",{"id":4159,"data":4160,"type":24,"maxContentLevel":34,"version":24,"reviews":4163},"2ed030f7-eeb2-47e3-a531-614e3e4d9f99",{"type":24,"markdownContent":4161,"audioMediaId":4162},"**Epistasis**, the interaction between genes, can create complex adaptations by modifying the effects of individual genes. These interactions can lead to the emergence of new traits that enhance an organism's ability to survive and reproduce in its environment.\n\n![Graph](image://d473e421-e9bb-4590-8e0c-f08f8c27323c \"Epistatic hair by Thomas Shafee (CC BY 4.0) \u003Chttps://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons\")\n\nIn the case of **maize (corn),** epistasis plays a significant role in the plant's adaptation to different environmental conditions. The interaction between multiple genes involved in flowering time has allowed maize to be cultivated across a wide range of latitudes and climates.\n\nThese gene interactions enable maize to adapt its growth cycle to the local growing season, which is crucial for maximizing yield in various environments. The complexity of epistatic interactions in maize highlights how adaptation can result from the interplay of multiple genes, rather than changes in a single gene.\n\n**Adaptation** is a dynamic and multifaceted process that arises from the interplay of various genetic mechanisms.\n\nWhether through mutation, genetic drift, hidden variation, gene flow, or epistasis, organisms continually evolve traits that enhance their survival and reproductive success in specific environments.\n\nThe examples discussed—from antibiotic-resistant bacteria to the diverse adaptations of plants and animals—illustrate the diverse ways in which adaptation manifests across the tree of life.","c0f32601-09dc-414c-8ecd-d62377ea1d83",[4164],{"id":4165,"data":4166,"type":67,"version":24,"maxContentLevel":34},"5e23d37d-a117-4e44-bd80-f4da98f2591c",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4167,"multiChoiceCorrect":4169,"multiChoiceIncorrect":4171,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4168],"What is the interaction between genes that can create complex adaptations called?",[4170],"Epistasis",[4113,4172,3098],"Hidden Genetic Variation",{"id":4174,"data":4175,"type":25,"version":25,"maxContentLevel":34,"summaryPage":4177,"introPage":4185,"pages":4191},"96b215b5-6878-4491-82b8-675137a4d101",{"type":25,"title":4176},"Speciation",{"id":4178,"data":4179,"type":34,"maxContentLevel":34,"version":24},"50bf02ae-f1b7-4b6e-9386-492d52377281",{"type":34,"summary":4180},[4181,4182,4183,4184],"Speciation creates new species through reproductive isolation.","Allopatric speciation involves geographic separation and genetic divergence.","Sympatric speciation happens without geographic barriers.","Prezygotic and postzygotic mechanisms prevent interbreeding.",{"id":4186,"data":4187,"type":53,"maxContentLevel":34,"version":24},"09a0eb70-747d-429a-8c0e-22810e01586d",{"type":53,"intro":4188},[4189,4190],"What stops different species from breeding?","What different forms of evolution cause new species to arise?",[4192,4242,4271,4306],{"id":4193,"data":4194,"type":24,"maxContentLevel":34,"version":25,"reviews":4197},"3a91edf3-9f71-4bc5-9d1c-3aa379a4e40c",{"type":24,"markdownContent":4195,"audioMediaId":4196},"A **species** is defined as a group of organisms that can interbreed and produce fertile offspring under natural conditions.\n\n**Speciation**, the process by which new species arise, occurs when populations that once belonged to **the same species stop being able to interbreed.**\n\nIn terms of the causes of speciation, two major types are often distinguished: **allopatric** and **sympatric** speciation.\n\n**Allopatric** speciation happens when populations are geographically isolated by physical barriers like mountains or rivers, leading to genetic divergence as they adapt to different environments.\n\nA classic example is the snapping shrimp populations on either side of the Isthmus of Panama. Once the land bridge formed, these populations became geographically separated and evolved independently, eventually becoming so distinct that they could no longer interbreed.\n\n![Graph](image://4eacf755-afdd-430f-9461-e98874125ac9 \"Isthmus of Panama (closure) - Speciation of marine organisms (w annot) by Andrew Z. Colvin (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nOn the other hand, **sympatric speciation** occurs without geographic isolation, for example, due to random chromosomal changes, or niche behavioral changes within a subset of a population.\n\nBut what actually prevents these species from breeding? What are the mechanisms?","f8c11e59-822a-43d4-a742-91ef7d1d2717",[4198,4209,4221,4232],{"id":4199,"data":4200,"type":67,"version":24,"maxContentLevel":34},"17a90e65-e177-4edb-8238-577648b8ceac",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4201,"multiChoiceCorrect":4203,"multiChoiceIncorrect":4205,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4202],"What is the definition of a species?",[4204],"A group of organisms that can interbreed and produce fertile offspring",[4206,4207,4208],"A group of organisms that live in the same habitat","A group of organisms that share the same diet","A group of organisms that have the same physical appearance",{"id":4210,"data":4211,"type":67,"version":24,"maxContentLevel":34},"e4301483-c326-484f-8dd1-aa82f7b2ec23",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4212,"multiChoiceCorrect":4214,"multiChoiceIncorrect":4217,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[4213],"Which of the following are types of speciation?",[4215,4216],"Allopatric","Sympatric",[4218,4219,4220],"Temporal","Behavioral","Mechanical",{"id":4222,"data":4223,"type":67,"version":24,"maxContentLevel":34},"46644009-76af-4fdd-add2-7ecd0cf867fc",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4224,"multiChoiceCorrect":4226,"multiChoiceIncorrect":4228,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4225],"What causes allopatric speciation?",[4227],"Geographic isolation",[4229,4230,4231],"Chromosomal changes","Behavioral changes","Ecological isolation",{"id":4233,"data":4234,"type":67,"version":24,"maxContentLevel":34},"80120bb2-8554-4ba9-8abf-6b91f595a74f",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4235,"multiChoiceCorrect":4237,"multiChoiceIncorrect":4239,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[4236],"What are the causes of sympatric speciation?",[4229,4238],"Niche behavioral changes",[4227,4240,4241],"Temporal isolation","Mechanical isolation",{"id":4243,"data":4244,"type":24,"maxContentLevel":34,"version":24,"reviews":4247},"6070459d-9446-4154-8bbe-349feea430f5",{"type":24,"markdownContent":4245,"audioMediaId":4246},"Diverging populations of species are prevented from breeding, and therefore prevented from exchanging their genes, due to mechanisms of reproductive isolation.\n\nAs reproductive isolation mechanisms take hold, populations accumulate genetic, behavioral, and morphological differences, leading to the formation of distinct species.\n\nWe’re going to explore some of these isolation mechanisms in this orb.\n\nBut the first thing to note, however, is that **reproductive isolation** can occur at different stages in the reproductive process, and it’s typically categorized into **prezygotic** and **postzygotic** isolation mechanisms.\n\nA zygote (you may remember) is the cell formed when a sperm fertilizes an egg.\n\nSo **prezygotic mechanisms** prevent this from happening, while **postzygotic mechanisms** act after a zygote has formed.\n\nEssentially, prezygotic mechanisms prevent mating or fertilization from occurring in the first place. These mechanisms act before the formation of a zygote.\n\nMeanwhile, postzygotic mechanisms operate after fertilization and typically result in the offspring being inviable or infertile.","8aeaf9ae-752b-458d-a5b6-d8cad8950446",[4248,4259],{"id":4249,"data":4250,"type":67,"version":24,"maxContentLevel":34},"665d27fc-6f12-4aba-b73d-29d55ec9bade",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4251,"multiChoiceCorrect":4253,"multiChoiceIncorrect":4255,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4252],"What does reproductive isolation prevent?",[4254],"Diverging populations from exchanging genes",[4256,4257,4258],"Populations from adapting to new environments","Species from becoming extinct","Organisms from migrating",{"id":4260,"data":4261,"type":67,"version":24,"maxContentLevel":34},"c6cdc325-60e1-42cc-85a2-4fb820b31f95",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":4262,"matchPairsPairs":4264,"matchPairsShowExamples":6},[4263],"Match the type of of reproductive isolation to its description:",[4265,4268],{"left":4266,"right":4267,"direction":34},"Prezygotic isolation","Prevents mating or fertilization",{"left":4269,"right":4270,"direction":34},"Postzygotic isolation","Operate after mating or fertilization",{"id":4272,"data":4273,"type":24,"maxContentLevel":34,"version":24,"reviews":4276},"4a263a3a-d2d4-4d74-bf23-c6bb97539385",{"type":24,"markdownContent":4274,"audioMediaId":4275},"Prezygotic isolation mechanisms can take several forms: **temporal**, **behavioral**, **mechanical**, and ecological.\n\n**Temporal isolation** occurs when populations breed at different times.\n\nFor example, in the grass Anthoxanthum odoratum, populations in contaminated soils have adapted to flower at different times than those in uncontaminated soils. This timing difference prevents interbreeding because the two populations are reproductively active at different periods, even though they are geographically close.\n\n**Behavioral isolation** arises when differences in mating behaviors or rituals prevent populations from mating.\n\nThe apple maggot fly (Rhagoletis pomonella) provides a clear example. Originally, these flies laid eggs on hawthorn fruits, but a portion of the population shifted to apples. Over time, this difference led to reproductive isolation despite living in the same geographic area.\n\n**Mechanical isolation** occurs when physical differences in reproductive structures prevent successful mating.\n\nIn many insect species, the shape of the genitalia is species-specific. Even slight morphological differences can make mating impossible, ensuring that different species do not interbreed even if they come into contact.\n\n**Ecological isolation** happens when populations adapt to different habitats within the same geographic area, reducing the likelihood of encounters and mating. Heliconius butterflies, for example, occupy distinct microhabitats within the same region. These ecological differences prevent interbreeding between species, contributing to reproductive isolation.","ca749c96-4e79-4cc6-97de-b5fb12d393b2",[4277,4292],{"id":4278,"data":4279,"type":67,"version":24,"maxContentLevel":34},"6e8c0fb4-3575-4036-8875-5e9e80ad3789",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":4280,"matchPairsPairs":4282,"matchPairsShowExamples":6},[4281],"Match the types of prezygotic isolation to their mechanisms:",[4283,4285,4288,4290],{"left":4240,"right":4284,"direction":34},"Populations breed at different times",{"left":4286,"right":4287,"direction":34},"Behavioral isolation","Differences in mating behaviors prevent mating",{"left":4241,"right":4289,"direction":34},"Physical differences in reproductive structures prevent mating",{"left":4231,"right":4291,"direction":34},"Populations adapt to different habitats within the same area",{"id":4293,"data":4294,"type":67,"version":24,"maxContentLevel":34},"218effb8-ccb7-4c26-87c3-389d51ad2b20",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":4295,"matchPairsPairs":4297,"matchPairsShowExamples":6},[4296],"Match the types of prezygotic isolation to an example:",[4298,4300,4302,4304],{"left":4240,"right":4299,"direction":34},"Anthoxanthum odoratum in contaminated vs. uncontaminated soils",{"left":4286,"right":4301,"direction":34},"Apple maggot fly shifting from hawthorn to apples",{"left":4241,"right":4303,"direction":34},"the male and female genitalia of some tropical butterflies are highly specific to their counterparts",{"left":4231,"right":4305,"direction":34},"Heliconius butterflies in distinct microhabitats",{"id":4307,"data":4308,"type":24,"maxContentLevel":34,"version":24,"reviews":4311},"79e413a4-ba58-4ef4-b39a-6cc71b70baf0",{"type":24,"markdownContent":4309,"audioMediaId":4310},"When **prezygotic barriers** fail and mating occurs, **postzygotic isolation mechanisms** come into play.\n\nThese mechanisms operate after fertilization and typically result in the offspring being inviable or infertile. This means that even if a sperm fertilizes an egg, the resulting zygote either does not develop into a viable offspring, or if it does, the offspring cannot reproduce.\n\n**Hybrid inviability** is an example of **postzygotic isolation**, where hybrid offspring fail to develop properly or are too weak to survive. This often results from genetic incompatibilities that arise as populations diverge. For instance, when different subspecies of the European house mouse interbreed, their offspring often suffer from developmental issues due to chromosomal differences, leading to inviability.\n\nHybrid sterility occurs when hybrid offspring are viable but unable to reproduce. A well-known example is the mule, a hybrid between a horse and a donkey.\n\n![Graph](image://0946e146-1045-4953-8132-0ddfc21dc304 \"Juancito (Public domain), via Wikimedia Commons\")\n\nMules are almost always sterile because horses and donkeys have different chromosome numbers, which prevents the proper formation of gametes (sperm or eggs) in the hybrids. This sterility stops gene flow between the parent species, reinforcing their separation.\n\nChromosome changes, such as what is known as **polyploidy**, a condition where an organism has more than two complete sets of chromosomes, are also significant drivers of speciation, particularly in plants.\n\nIn some cases, the first-generation hybrids are viable and fertile, but their offspring, the second generation, suffer from hybrid breakdown—they may be sterile or inviable.","f27b7f09-796b-477b-be4f-813158151dcc",[4312,4320,4334,4344],{"id":4313,"data":4314,"type":67,"version":24,"maxContentLevel":34},"c9a38c60-4a4a-4549-ad25-c928385d2d36",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4315,"multiChoiceCorrect":4317,"multiChoiceIncorrect":4319,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4316],"What is the result of postzygotic isolation mechanisms?",[4318],"Inviable or infertile offspring",[4227,4230,4240],{"id":4321,"data":4322,"type":67,"version":24,"maxContentLevel":34},"42fe4bfe-06fb-4518-94c3-2eb3add59142",{"type":67,"reviewType":128,"spacingBehaviour":24,"matchPairsQuestion":4323,"matchPairsPairs":4324,"matchPairsShowExamples":6},[178],[4325,4328,4331],{"left":4326,"right":4327,"direction":34},"Hybrid inviability","Offspring fail to develop properly or are too weak to survive",{"left":4329,"right":4330,"direction":34},"Hybrid sterility","Offspring are viable but unable to reproduce",{"left":4332,"right":4333,"direction":34},"Hybrid breakdown","Only first-generation hybrids are viable and fertile",{"id":4335,"data":4336,"type":67,"version":24,"maxContentLevel":34},"83ea058a-2045-4343-9591-fc3c13bc8fc9",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4337,"multiChoiceCorrect":4339,"multiChoiceIncorrect":4341,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4338],"What is 'polyploidy', a significant driver of speciation in plants?",[4340],"Organism has more than two complete sets of chromosomes",[4342,4343,4284],"Hybrid offspring fail to develop properly","Hybrid offspring are viable but unable to reproduce",{"id":4345,"data":4346,"type":67,"version":24,"maxContentLevel":34},"770ccfe6-77b9-48da-8f88-f801e383cbcd",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4347,"multiChoiceCorrect":4349,"multiChoiceIncorrect":4351,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4348],"Which example illustrates allopatric speciation?",[4350],"Snapping shrimp population separated by the Isthmus of Panama",[4301,4352,4353],"Howea palms on Lord Howe Island diverging due to differences in flowering time and habitat","Cichlid fish in Lake Malawi diversifying into over 500 species",{"id":4355,"data":4356,"type":25,"version":24,"maxContentLevel":34,"summaryPage":4358,"introPage":4366,"pages":4372},"dd83cd23-2aa6-4ca4-89fb-ef9f963ae101",{"type":25,"title":4357},"Concluding the Pathway",{"id":4359,"data":4360,"type":34,"maxContentLevel":34,"version":24},"dac8e26e-3a90-41a6-9ce5-748b983c3183",{"type":34,"summary":4361},[4362,4363,4364,4365],"Life is growth, reproduction, response, metabolism, homeostasis, evolution.","Cell theory: all life is made of cells.","Evolution explains life's diversity and adaptability.","Biology evolves with discoveries like endosymbiotic theory.",{"id":4367,"data":4368,"type":53,"maxContentLevel":34,"version":24},"e4fb1095-c149-45e3-89bc-4d16e6b9c026",{"type":53,"intro":4369},[4370,4371],"What is the smallest unit capable of carrying out life's essential functions?","How does the endosymbiotic theory connect evolution and cellular biology?",[4373,4412,4417],{"id":4374,"data":4375,"type":24,"maxContentLevel":34,"version":24,"reviews":4378},"497bf357-efb6-4fab-9da8-6ca38a9dfac9",{"type":24,"markdownContent":4376,"audioMediaId":4377},"You’ve now reached the end of the pathway ‘The Core Concepts of Biology’. Congratulations!\n\nWe started off the pathway asking the question ‘What is Life?’. So let's end by reflecting on how far we have answered that question.\n\n*What have we learned?*\n\nWell, firstly, we have learned that the concept of \"life\", while intuitively understood, is surprisingly difficult to define precisely.\n\n![Graph](image://d6b8781a-b1fa-4b49-bee3-7a6657ab2b57 \"HumanNewborn by Ernest F (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")\n\nAt its most basic level, life refers to entities that exhibit certain characteristics, including **growth**, **reproduction**, **response to stimuli, metabolism, homeostasis,** and **evolution over time**. Organisms like bacteria, plants, and animals share these features, distinguishing them from non-living things such as rocks or machines.\n\nWe have also learned that the field of biology's core concepts provide a framework for understanding the principles underlying life.\n\nThe development of these ideas, such as cell theory, gene theory, and evolution, marked important historical milestones in our scientific understanding.","c91b0a40-5107-4677-ac98-2d53568fa1e8",[4379,4390,4401],{"id":4380,"data":4381,"type":67,"version":24,"maxContentLevel":34},"08c19306-5c31-49d1-8532-108e4afb2119",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4382,"multiChoiceCorrect":4384,"multiChoiceIncorrect":4387,"multiChoiceMultiSelect":21,"multiChoiceRevealAnswerOption":6},[4383],"Which of the following statements are true about the 'Endosymbiotic Theory'?",[4385,4386],"Bridges gap between evolution and cellular biology","Suggests complex cells arose through symbiotic relationships",[4388,4389],"Explains the origin of DNA","Describes the process of natural selection",{"id":4391,"data":4392,"type":67,"version":24,"maxContentLevel":34},"8721f64a-51cc-4144-aca6-7e29819d591c",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4393,"multiChoiceCorrect":4395,"multiChoiceIncorrect":4397,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4394],"What does epigenetics reveal about gene expression?",[4396],"Environment can influence gene expression",[4398,4399,4400],"Genes are fixed and unchangeable","Only mutations can change gene expression","Gene expression is solely determined by DNA sequence",{"id":4402,"data":4403,"type":67,"version":24,"maxContentLevel":34},"81c4192e-2dc0-4d8a-a8a8-8a85bfbea00e",{"type":67,"reviewType":34,"spacingBehaviour":24,"multiChoiceQuestion":4404,"multiChoiceCorrect":4406,"multiChoiceIncorrect":4408,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[4405],"What does the concept of the 'microbiome' show?",[4407],"Diverse communities of microorganisms are essential to host's health and functioning",[4409,4410,4411],"All organisms are self-sufficient","Microbes are harmful to larger organisms","Only plants have microbiomes",{"id":4413,"data":4414,"type":24,"maxContentLevel":34,"version":24},"0ff223c5-7a31-49f4-b9df-5d73d3180f87",{"type":24,"markdownContent":4415,"audioMediaId":4416},"Understanding these features and core concepts has been the result of centuries of scientific progress, shaped by discoveries that continually deepen our view of what it means to be alive.\n\nCell theory, for example, showed that all living organisms are composed of cells, the smallest units capable of carrying out the functions essential for life.\n\nWhether we’re talking about a single bacterium or a human being, the cell remains the fundamental building block of life.\n\n![Graph](image://cd120db5-a6b4-4b05-a740-329023cd9095 \"Cork Micrographia Hooke (Public domain), via Wikimedia Commons\")\n\n**Gene theory** added another layer by explaining the flow of genetic information through DNA, the molecule that carries the instructions for life’s processes. The discovery of metabolism explained how organisms convert energy to sustain themselves, while homeostasis showed how they maintain stable internal conditions amidst changing external environments.\n\n![Graph](image://f75e55f0-9da9-40c1-8f57-3c5c553697ed \"DNA double helix 45 (Public domain), via Wikimedia Commons\")\n\nFinally, Darwin’s **theory of evolution** by natural selection provided the unifying explanation for life’s diversity and the adaptability of organisms to their environments. Evolution remains the thread that ties all these concepts together, explaining how life changes over time, driven by variation, inheritance, and selection.\n\n![Graph](image://2ab4eb22-dd21-4b45-85cb-a74729eb59b2 \"Primate skull series with legend by Christopher Walsh, Harvard Medical School (CC BY 2.5) \u003Chttps://creativecommons.org/licenses/by/2.5>, via Wikimedia Commons\")","c8cde72f-bc01-4fd6-b05e-38fade43ba2f",{"id":4418,"data":4419,"type":24,"maxContentLevel":34,"version":24},"93bce737-f39e-41dd-9069-e4d48db8e863",{"type":24,"markdownContent":4420,"audioMediaId":4421},"Yet, even as these core concepts continue to guide our understanding, biology—like life itself—is evolving.\n\nWhile these foundational ideas still hold, new discoveries keep expanding our understanding.\n\nA perfect example of this is the **endosymbiotic theory**, which bridges the gap between evolution and cellular biology. It suggests that complex cells, like those in plants and animals, arose through a symbiotic relationship between ancient single-celled organisms.\n\nThis theory not only deepens our understanding of cellular structures but also ties it to the grand narrative of evolution, showing how collaboration at the microscopic level shaped the complexity of life we see today.\n\nSimilarly, fields like **epigenetics** have revealed that the environment can influence how genes are expressed, challenging earlier notions of inheritance.\n\nAnd the exploration of the **microbiome** has shown us that no organism exists in isolation, with vast networks of microbes influencing the health and survival of larger organisms.\n\n![Graph](image://21ba5cb7-8d2f-4e8d-a31d-74c7e373dcc4 \"Marine animals and their associated microbiomes. Image by Amy Apprill (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nIt's clear that life’s complexity continues to offer new mysteries to explore, and the core concepts you’ve learned in this pathway should provide the foundation for further building on your understanding.","298348c9-96ae-4017-8997-8525b19c08a2",{"left":4,"top":4,"width":4423,"height":4423,"rotate":4,"vFlip":6,"hFlip":6,"body":4424},24,"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"m9 18l6-6l-6-6\"/>",{"left":4,"top":4,"width":4423,"height":4423,"rotate":4,"vFlip":6,"hFlip":6,"body":4426},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M12.586 2.586A2 2 0 0 0 11.172 2H4a2 2 0 0 0-2 2v7.172a2 2 0 0 0 .586 1.414l8.704 8.704a2.426 2.426 0 0 0 3.42 0l6.58-6.58a2.426 2.426 0 0 0 0-3.42z\"/>\u003Ccircle cx=\"7.5\" cy=\"7.5\" r=\".5\" fill=\"currentColor\"/>\u003C/g>",1778179487803]