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DNA is stored there.","Organelles like mitochondria power eukaryotic cells, boosting efficiency.",1,{"id":38,"data":39,"type":40,"maxContentLevel":19,"version":36},"43d94c71-bf11-4b1c-9866-6f2e7468fabe",{"type":40,"intro":41},10,[42,43],"What are the two main kinds of cell and the difference between them?","Why are mitochondria called the power plants of the cell?",[45,65,96,131,173],{"id":46,"data":47,"type":36,"maxContentLevel":19,"version":19,"reviews":50},"422778bb-885a-4d4e-ac74-fc6a691f914c",{"type":36,"markdownContent":48,"audioMediaId":49},"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",[51],{"id":52,"data":53,"type":54,"version":25,"maxContentLevel":19},"794d27cf-6f85-4b31-b424-4dcdcea70078",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":55,"multiChoiceCorrect":57,"multiChoiceIncorrect":60,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},11,[56],"Which of the following are characteristics of prokaryotic cells?",[58,59],"Found in bacteria and archaea","Lacks a defined nucleus",[61,62,63],"Contains a defined nucleus","Found in plants, animals, and fungi","Contain specialized parts (organelles)",true,{"id":66,"data":67,"type":36,"maxContentLevel":19,"version":27,"reviews":70},"cfef124f-df74-48db-a507-54e513b59b8e",{"type":36,"markdownContent":68,"audioMediaId":69},"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",[71,83],{"id":72,"data":73,"type":54,"version":19,"maxContentLevel":19},"5d16c169-b6b3-4c73-8e6e-7208ed05764e",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":74,"multiChoiceCorrect":76,"multiChoiceIncorrect":80,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[75],"What is the function of the cell membrane?",[77,78,79],"Controls entry and exit of materials","Protection","Helps the cell communicate with its surroundings",[81,82],"Stores DNA","Captures sunlight for photosynthesis",{"id":84,"data":85,"type":54,"version":25,"maxContentLevel":19},"f04fab5b-c2e2-4398-942e-10bc3389dd07",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":86,"multiChoiceCorrect":88,"multiChoiceIncorrect":93,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[87],"Which of the following statements describe the cytoplasm?",[89,90,91,92],"Jelly-like substance","Composed mostly of water","Contains dissolved nutrients, salts, proteins","Medium for organelles to operate within a cell",[94,95],"Made of fat and proteins","Enclosed by nuclear envelope",{"id":97,"data":98,"type":36,"maxContentLevel":19,"version":25,"reviews":101},"b764cb18-b3ec-4492-a92a-fd7afb289b71",{"type":36,"markdownContent":99,"audioMediaId":100},"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",[102,122],{"id":103,"data":104,"type":54,"version":36,"maxContentLevel":19},"b41bce7c-2dda-441b-80da-dcd35a566684",{"type":54,"reviewType":19,"spacingBehaviour":36,"collapsingSiblings":105,"multiChoiceQuestion":108,"multiChoiceCorrect":110,"multiChoiceIncorrect":112,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":116,"matchPairsPairs":118},[106,107],"14ccef0c-b96d-4498-9811-f8a3951a3bb0","7254f19e-b494-411b-b5d8-9d95e48c636c",[109],"What are ribosomes crucial for?",[111],"Protein synthesis",[113,114,115],"Storing DNA","Converting nutrients to ATP","Capturing sunlight for photosynthesis",[117],"Match the pairs below:",[119],{"left":120,"right":121,"direction":19},"Ribosomes","Crucial for protein synthesis",{"id":123,"data":124,"type":54,"version":25,"maxContentLevel":19},"7e44ef78-5627-4cec-8191-e825cefc2828",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":125,"multiChoiceCorrect":127,"multiChoiceIncorrect":130,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[126],"Which of the following statements describe the nucleus?",[128,81,95,129],"Large, spherical structure","Sends instructions to cell",[77,58],{"id":132,"data":133,"type":36,"maxContentLevel":19,"version":25,"reviews":136},"9e4e90fa-494a-4009-9fea-02163fafb444",{"type":36,"markdownContent":134,"audioMediaId":135},"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",[137,152],{"id":107,"data":138,"type":54,"version":36,"maxContentLevel":19},{"type":54,"reviewType":19,"spacingBehaviour":36,"collapsingSiblings":139,"multiChoiceQuestion":140,"multiChoiceCorrect":142,"multiChoiceIncorrect":144,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":147,"matchPairsPairs":148},[103,106],[141],"What is the primary function of mitochondria?",[143],"Producing usable energy (ATP) through cellular respiration",[145,146,115],"Storing DNA in the nucleus","Controlling entry and exit of materials",[117],[149],{"left":150,"right":151,"direction":19},"Mitochondria","Produces usable energy (ATP) through cellular respiration",{"id":153,"data":154,"type":54,"version":36,"maxContentLevel":19},"62634d5f-07ee-4b01-98b9-02c51432efcc",{"type":54,"reviewType":155,"spacingBehaviour":36,"matchPairsQuestion":156,"matchPairsPairs":158,"matchPairsShowExamples":6},6,[157],"Match the component of the cell with its analogy in a factory:",[159,162,165,167,170],{"left":160,"right":161,"direction":19},"Cell Membrane","Factory perimeter",{"left":163,"right":164,"direction":19},"Cytoplasm","Factory floor, where everything is located",{"left":120,"right":166,"direction":19},"Assembly machines",{"left":168,"right":169,"direction":19},"DNA","Blueprints",{"left":171,"right":172,"direction":19},"Nucleus","Central office",{"id":174,"data":175,"type":36,"maxContentLevel":19,"version":25,"reviews":178},"083e9a89-5c7d-40a3-aeed-59b0de6c23bb",{"type":36,"markdownContent":176,"audioMediaId":177},"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",[179],{"id":180,"data":181,"type":54,"version":25,"maxContentLevel":19},"239ccb70-ea3d-4986-bcd0-31d7518cf4bf",{"type":54,"reviewType":155,"spacingBehaviour":36,"matchPairsQuestion":182,"matchPairsPairs":183,"matchPairsShowExamples":6},[117],[184,186,189,192,195],{"left":150,"right":185,"direction":19},"Site of cellular respiration, providing usable energy (ATP)",{"left":187,"right":188,"direction":19},"Rough Endoplasmic Reticulum (ER)","Covered in ribosomes, processes proteins",{"left":190,"right":191,"direction":19},"Smooth Endoplasmic Reticulum (ER)","Detoxifies cell, produces lipids",{"left":193,"right":194,"direction":19},"Golgi Apparatus","Shipping department of the cell (packages and sends proteins)",{"left":196,"right":197,"direction":19},"Chloroplasts","Solar panels of the cell (capture sunlight for photosynthesis)",{"id":199,"data":200,"type":25,"version":25,"maxContentLevel":19,"summaryPage":202,"introPage":210,"pages":216},"d9ed0cb6-e9a5-409c-ae46-39aaaf235713",{"type":25,"title":201},"Reproduction",{"id":203,"data":204,"type":19,"maxContentLevel":19,"version":36},"49847c96-ec0d-4995-833b-5b47897e9dc5",{"type":19,"summary":205},[206,207,208,209],"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":211,"data":212,"type":40,"maxContentLevel":19,"version":36},"7c3e9399-cc35-4e25-b26d-5c51a9d03043",{"type":40,"intro":213},[214,215],"How does binary fission work in bacteria?","What makes sexual reproduction a game-changer for genetic diversity?",[217,260,299,329],{"id":218,"data":219,"type":36,"maxContentLevel":19,"version":25,"reviews":222},"4507656c-3601-401d-80c7-04d65dd6b0cf",{"type":36,"markdownContent":220,"audioMediaId":221},"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",[223,235,253],{"id":224,"data":225,"type":54,"version":25,"maxContentLevel":19},"e5ec117a-d4f2-4b92-a0c9-d7fbe22eaae2",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":226,"multiChoiceCorrect":228,"multiChoiceIncorrect":233,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[227],"Which organisms can reproduce asexually?",[229,230,231,232],"Bacteria","Some plants","Some fungi","Some simple animals",[234],"Some mammals",{"id":236,"data":237,"type":54,"version":36,"maxContentLevel":19},"99f9ccf3-cee6-48d3-a3b4-d03a007a0d4f",{"type":54,"reviewType":19,"spacingBehaviour":36,"collapsingSiblings":238,"multiChoiceQuestion":242,"multiChoiceCorrect":244,"multiChoiceIncorrect":246,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":249,"matchPairsPairs":250},[239,240,241],"ca8dc0e3-ffae-46d0-a0cc-145330525d59","5cd48b81-86af-4a90-9ad4-8c2ce1c43cb6","78c37361-6cee-4b81-a3b0-fc3c3991ab71",[243],"What is asexual reproduction?",[245],"Single parent produces genetically identical offspring",[247,248],"Two parents produces genetically identical offspring","Single parent produces genetically diverse offspring",[117],[251],{"left":252,"right":245,"direction":19},"Asexual Reproduction",{"id":254,"data":255,"type":54,"version":25,"maxContentLevel":19},"45ebcd34-eecf-4b7f-84ed-24dcfeae2d38",{"type":54,"reviewType":36,"spacingBehaviour":36,"activeRecallQuestion":256,"activeRecallAnswers":258},[257],"What is a negative consequence of asexual reproduction?",[259],"Offspring vulnerable to same environmental threats as the parent",{"id":261,"data":262,"type":36,"maxContentLevel":19,"version":25,"reviews":265},"45b777f0-3f9b-4459-aa92-55ecee4acd57",{"type":36,"markdownContent":263,"audioMediaId":264},"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",[266,276,287],{"id":267,"data":268,"type":54,"version":36,"maxContentLevel":19},"22f1e78b-c7df-44b4-aa23-2c50aed2945d",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":269,"multiChoiceCorrect":271,"multiChoiceIncorrect":272,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[270],"Which organism commonly reproduces through binary fission?",[229],[273,274,275],"Plants","Fungi","Reptiles",{"id":277,"data":278,"type":54,"version":25,"maxContentLevel":19},"35035fed-41c9-4b62-83e3-ecef7cc767e4",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":279,"multiChoiceCorrect":281,"multiChoiceIncorrect":284,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[280],"What are the two steps involved in binary fission?",[282,283],"Step 1: Cell duplicates genetic material","Step 2: Cell grows larger and splits into two identical daughter cells",[285,286],"Step 1: Cell forms a bud","Step 2: Cell fuses with another cell",{"id":288,"data":289,"type":54,"version":36,"maxContentLevel":19},"5c8ec8ab-580c-4831-812a-adfb3dbd57ba",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":290,"multiChoiceCorrect":292,"multiChoiceIncorrect":295,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[291],"Which of the below applies to budding?",[293,294],"Small outgrowth forms on parent cell and becomes independent cell","Observed in Saccharomyces cerevisiae (yeast)",[296,297,298],"Involves fusion of gametes","Results in genetically diverse offspring","Occurs in bacteria",{"id":300,"data":301,"type":36,"maxContentLevel":19,"version":36,"reviews":304},"787e879a-a944-46da-b8bb-3a89ef3bf31e",{"type":36,"markdownContent":302,"audioMediaId":303},"**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",[305,317],{"id":306,"data":307,"type":54,"version":36,"maxContentLevel":19},"215fe1da-23c4-4f0c-aaa0-c21ca84b04a6",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":308,"multiChoiceCorrect":310,"multiChoiceIncorrect":314,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[309],"Which of the below apply to gametes?",[311,312,313],"Produced through meiosis","Two types: sperm (male) and egg (female)","Specialized sex cells",[315,316],"Formed by binary fission","Genetically identical to parent",{"id":318,"data":319,"type":54,"version":36,"maxContentLevel":19},"e69e94ac-058d-4551-92c9-19b0d9113104",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":320,"multiChoiceCorrect":322,"multiChoiceIncorrect":326,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[321],"Which of the below apply to meiosis?",[323,324,325],"Type of cell division","Reduces number of chromosomes by half","Produces gametes",[327,328],"Produces zygotes","Maintains whole set of chromosomes",{"id":330,"data":331,"type":36,"maxContentLevel":19,"version":36,"reviews":334},"e1a787a9-58c2-43fd-8ba9-f6f6a9206e5b",{"type":36,"markdownContent":332,"audioMediaId":333},"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",[335,342,351],{"id":336,"data":337,"type":54,"version":36,"maxContentLevel":19},"af7a38d9-abaa-4bc3-ac3a-57018800ea77",{"type":54,"reviewType":27,"spacingBehaviour":36,"clozeQuestion":338,"clozeWords":340},[339],"During fertilization, the male gamete and the female gamete fuse to form a zygote. ",[341],"zygote",{"id":343,"data":344,"type":54,"version":36,"maxContentLevel":19},"5406f46f-9c62-4afe-889d-ea0970c8be4c",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":345,"multiChoiceCorrect":347,"multiChoiceIncorrect":349,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[346],"Which of the below statements apply to zygotes?",[348],"Contain a complete set of chromosomes (diploid)",[311,316,350],"Contain a half a set of chromosomes (haploid)",{"id":352,"data":353,"type":54,"version":36,"maxContentLevel":19},"a8e35cd3-a070-47c1-92d1-d5380eb5f93e",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":354,"multiChoiceCorrect":356,"multiChoiceIncorrect":359,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[355],"Why is the genetic diversity created by sexual reproduction important?",[357,358],"Enables organisms to resist diseases","Facilitates adaptation for changing environments",[360,361,362],"Leads to identical offspring","Reduces population growth","Increases vulnerability to diseases",{"id":364,"data":365,"type":25,"version":19,"maxContentLevel":19,"summaryPage":367,"introPage":375,"pages":381,"reviews":501},"d759992f-3e4d-41f6-b26c-6372deaf800a",{"type":25,"title":366},"Growth and Development",{"id":368,"data":369,"type":19,"maxContentLevel":19,"version":36},"d2d671dd-375d-49e6-b650-b164b8e8f89f",{"type":19,"summary":370},[371,372,373,374],"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":376,"data":377,"type":40,"maxContentLevel":19,"version":36},"471b3dcb-7a69-4ae8-9f2c-f38307931448",{"type":40,"intro":378},[379,380],"How do unicellular organisms like E. coli grow and reproduce?","What role does cell differentiation play in multicellular organisms?",[382,407,446,484],{"id":383,"data":384,"type":36,"maxContentLevel":19,"version":25,"reviews":387},"4504116a-3cb1-4ac3-ad5f-bb73ee5b9aa9",{"type":36,"markdownContent":385,"audioMediaId":386},"**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",[388],{"id":389,"data":390,"type":54,"version":36,"maxContentLevel":19},"a1cfd6c7-86c3-4b36-a040-139bc4d744c0",{"type":54,"reviewType":19,"spacingBehaviour":36,"collapsingSiblings":391,"multiChoiceQuestion":394,"multiChoiceCorrect":396,"multiChoiceIncorrect":398,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":402,"matchPairsPairs":404},[392,393],"ef53db23-c80c-45d4-9d3d-7dd274d46744","5ed585ac-adca-4228-91fe-ddf387fa0ff0",[395],"Which process involves E. coli splitting into two daughter cells?",[397],"Binary Fission",[399,400,401],"Mitosis","Cell Differentiation","Metamorphosis",[403],"Match the type of biological process to an example of that process in action:",[405],{"left":397,"right":406,"direction":19},"E. coli splitting into two daughter cells",{"id":408,"data":409,"type":36,"maxContentLevel":19,"version":25,"reviews":412},"ae51a6df-dea1-4612-be4e-d4930ac4df64",{"type":36,"markdownContent":410,"audioMediaId":411},"**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",[413,428],{"id":239,"data":414,"type":54,"version":25,"maxContentLevel":19},{"type":54,"reviewType":19,"spacingBehaviour":36,"collapsingSiblings":415,"multiChoiceQuestion":416,"multiChoiceCorrect":418,"multiChoiceIncorrect":420,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":424,"matchPairsPairs":425},[240,241,236],[417],"What of the below describes the process of cell differentiation?",[419],"Unspecialized cells developing into specialized cell types",[421,422,423],"Specialized cells dividing to increase in number","Unspecialized cells dramatically growing in size","Unspecialized cells undergo binary fission",[117],[426],{"left":400,"right":427,"direction":19},"Unspecialized cells develop into specialized cell types",{"id":429,"data":430,"type":54,"version":36,"maxContentLevel":19},"c775953c-9c40-4ce5-b03d-a4e9bd9111a3",{"type":54,"reviewType":19,"spacingBehaviour":36,"collapsingSiblings":431,"multiChoiceQuestion":435,"multiChoiceCorrect":437,"multiChoiceIncorrect":439,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":442,"matchPairsPairs":443},[432,433,434],"a7d9a97f-4502-4b8b-85cd-ca1fc170a77f","dc60b074-63a3-45c2-935b-6cab53aeeb04","66080f81-fa22-41b7-b05f-a542c04720bb",[436],"Which of the following is an example of cell differentiation?",[438],"Stem cells becoming muscle cells, nerves, blood cells, forming organs",[406,440,441],"A tree growing from a shoot into woody tissue","A caterpillar transforming into a butterfly",[117],[444],{"left":400,"right":445,"direction":19},"Stem cells becoming muscle, nerve, blood cells, organs",{"id":447,"data":448,"type":36,"maxContentLevel":19,"version":25,"reviews":451},"52fc0ec2-a9c1-42ed-a750-ca2013aea013",{"type":36,"markdownContent":449,"audioMediaId":450},"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",[452,472],{"id":453,"data":454,"type":54,"version":25,"maxContentLevel":19},"0adbc440-b4c8-45d2-ae03-1f7a74834405",{"type":54,"reviewType":19,"spacingBehaviour":36,"collapsingSiblings":455,"multiChoiceQuestion":459,"multiChoiceCorrect":461,"multiChoiceIncorrect":463,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":467,"matchPairsPairs":468},[456,457,458],"fd5e32e5-a577-462e-8d8c-650a5d9d6806","90195c78-4794-4c3e-b18a-df2f97282f68","8dbf8af9-e84a-40d6-9018-647230c667de",[460],"What are the phases of the cell cycle?",[462],"Growth, DNA replication, division",[464,465,466],"Growth, differentiation, death","Replication, differentiation, death","Growth, replication, differentiation",[117],[469],{"left":470,"right":471,"direction":19},"Cell Cycle","Includes phases of growth, DNA replication, division",{"id":473,"data":474,"type":54,"version":36,"maxContentLevel":19},"a4c3ee45-c50a-4cda-af8e-f99314e6d0f9",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":475,"multiChoiceCorrect":477,"multiChoiceIncorrect":482,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[476],"Which of the below applies to mitosis?",[478,479,480,481],"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",[324,483],"Occurs for growth and development in prokaryotic cells",{"id":485,"data":486,"type":36,"maxContentLevel":19,"version":36,"reviews":489},"d08bc991-15cd-4d86-b839-eb6c758d755a",{"type":36,"markdownContent":487,"audioMediaId":488},"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",[490],{"id":491,"data":492,"type":54,"version":36,"maxContentLevel":19},"8057466c-fba2-4dcc-8602-3832c80cfbf8",{"type":54,"reviewType":19,"spacingBehaviour":36,"multiChoiceQuestion":493,"multiChoiceCorrect":495,"multiChoiceIncorrect":499,"multiChoiceMultiSelect":64,"multiChoiceRevealAnswerOption":6},[494],"Which of the following statements are true about metamorphosis?",[496,497,498],"Examples include caterpillar to butterfly transformation","Involves significant cellular reorganization and differentiation","Allows adaptation to new ecological roles",[500],"Can occur in unicellular organisms",[502],{"id":503,"data":504,"type":54,"version":36,"maxContentLevel":19},"5bf18767-4224-454a-ba28-c9a63785e939",{"type":54,"reviewType":155,"spacingBehaviour":36,"matchPairsQuestion":505,"matchPairsPairs":506,"matchPairsShowExamples":6},[117],[507,510],{"left":508,"right":509,"direction":19},"Meiosis","Daughter cells produce gametes, with half the number of chromosomes each",{"left":399,"right":511,"direction":19},"Daughter cells are genetically identical, with full set of chromosomes",{"id":513,"data":514,"type":25,"version":27,"maxContentLevel":19,"summaryPage":516,"introPage":524,"pages":530},"1009d9ec-ac67-4f12-96c5-8d2a5a2dbc7a",{"type":25,"title":515},"Adaption through Generations",{"id":517,"data":518,"type":19,"maxContentLevel":19,"version":36},"df0d94ff-39be-4fb6-82c4-d3496c6db9fa",{"type":19,"summary":519},[520,521,522,523],"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":525,"data":526,"type":40,"maxContentLevel":19,"version":36},"8685ec0a-736a-41bf-93e5-7df76bdadcc9",{"type":40,"intro":527},[528,529],"What makes a trait an adaptation?","How does adaptation differ from a simple response to the environment?",[531,552,572],{"id":532,"data":533,"type":36,"maxContentLevel":19,"version":36,"reviews":536},"5152f06f-1032-4b2e-aa6a-c24525af8615",{"type":36,"markdownContent":534,"audioMediaId":535},"**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",[537],{"id":458,"data":538,"type":54,"version":36,"maxContentLevel":19},{"type":54,"reviewType":19,"spacingBehaviour":36,"collapsingSiblings":539,"multiChoiceQuestion":540,"multiChoiceCorrect":542,"multiChoiceIncorrect":544,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":548,"matchPairsPairs":549},[453,456,457],[541],"What of the following applies to the concept of 'adaptation' in biology?",[543],"Explains how organisms evolve to survive and reproduce",[545,546,547],"Describes how organisms migrate to new environments","Explains how organisms develop new species","Describes how organisms remain unchanged over time",[117],[550],{"left":551,"right":543,"direction":19},"Adaptation",{"id":553,"data":554,"type":36,"maxContentLevel":19,"version":25,"reviews":557},"7bc66c75-4002-4bde-b36c-2813a45c582d",{"type":36,"markdownContent":555,"audioMediaId":556},"**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",[558],{"id":559,"data":560,"type":54,"version":36,"maxContentLevel":19},"ea5b6373-d677-493f-a583-ba260fc33ba9",{"type":54,"reviewType":155,"spacingBehaviour":36,"matchPairsQuestion":561,"matchPairsPairs":562,"matchPairsShowExamples":6},[117],[563,566,569],{"left":564,"right":565,"direction":19},"Behavioral Adaptations","Birds migrating to warmer climates during winter",{"left":567,"right":568,"direction":19},"Physiological Adaptations","Camels evolving to go long periods without water",{"left":570,"right":571,"direction":19},"Structural Adaptations","Thick fur of polar bears for insulation",{"id":573,"data":574,"type":36,"maxContentLevel":19,"version":19,"reviews":577},"c34d24f9-42db-4e09-a042-83dc164ed421",{"type":36,"markdownContent":575,"audioMediaId":576},"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",[578],{"id":579,"data":580,"type":54,"version":19,"maxContentLevel":19},"9e2f6961-631b-4228-afd9-cb482088e9e7",{"type":54,"reviewType":19,"spacingBehaviour":36,"collapsingSiblings":581,"multiChoiceQuestion":584,"multiChoiceCorrect":586,"multiChoiceIncorrect":588,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":592,"matchPairsPairs":593},[582,583],"acc126f4-f4be-49fe-93e8-bf0bb1d63665","a5e10126-8afd-4725-beb2-29b0bc91d4b5",[585],"Which of the below best describes natural selection?",[587],"Slow process occurring over many generations",[589,590,591],"Rapid process occurring within a single generation","Instantaneous change in traits","Unrelated to environmental changes",[117],[594],{"left":595,"right":587,"direction":19},"Natural Selection",[597,1018,1387,1702],{"id":23,"data":24,"type":25,"version":27,"maxContentLevel":19,"summaryPage":28,"introPage":37,"pages":598},[599,704,770,855,943],{"id":46,"data":47,"type":36,"maxContentLevel":19,"version":19,"reviews":50,"parsed":600},{"data":601,"body":604,"toc":702},{"title":602,"description":603},"","As we saw in the previous tile, defining 'What is life?' is best done by considering multiple core characteristics that living organisms share.",{"type":605,"children":606},"root",[607,614,619,624,634,639,650,669,679,687,697],{"type":608,"tag":609,"props":610,"children":611},"element","p",{},[612],{"type":613,"value":603},"text",{"type":608,"tag":609,"props":615,"children":616},{},[617],{"type":613,"value":618},"This tile introduces how organisms reproduce, grow, and develop—fundamental traits of all living things.",{"type":608,"tag":609,"props":620,"children":621},{},[622],{"type":613,"value":623},"But to understand reproduction and growth, we first need to grasp the basic structure of all life: the cell.",{"type":608,"tag":609,"props":625,"children":626},{},[627],{"type":608,"tag":628,"props":629,"children":633},"img",{"alt":630,"src":631,"title":632},"Graph","image://f4e3145d-1a23-40a4-8cc9-4349d2c720cb","General view of cells in the growing root-tip of the onion, via Wikimedia Commons",[],{"type":608,"tag":609,"props":635,"children":636},{},[637],{"type":613,"value":638},"All life, large or small, is made up of cells, and all cells are capable of carrying out the functions necessary for life.",{"type":608,"tag":609,"props":640,"children":641},{},[642,644],{"type":613,"value":643},"We’ll explore this further in our later tile on \"Cell Theory\", but for now, we're going to focus on ",{"type":608,"tag":645,"props":646,"children":647},"strong",{},[648],{"type":613,"value":649},"cell components.",{"type":608,"tag":609,"props":651,"children":652},{},[653,655,660,662,667],{"type":613,"value":654},"There are two main types of cells: ",{"type":608,"tag":645,"props":656,"children":657},{},[658],{"type":613,"value":659},"eukaryotic",{"type":613,"value":661}," and ",{"type":608,"tag":645,"props":663,"children":664},{},[665],{"type":613,"value":666},"prokaryotic",{"type":613,"value":668},".",{"type":608,"tag":609,"props":670,"children":671},{},[672,677],{"type":608,"tag":645,"props":673,"children":674},{},[675],{"type":613,"value":676},"Eukaryotic",{"type":613,"value":678}," 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.",{"type":608,"tag":609,"props":680,"children":681},{},[682],{"type":608,"tag":628,"props":683,"children":686},{"alt":630,"src":684,"title":685},"image://7e12f650-791a-44bc-9985-f9e79eae77a7","Image: SadiesBurrow, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons",[],{"type":608,"tag":609,"props":688,"children":689},{},[690,695],{"type":608,"tag":645,"props":691,"children":692},{},[693],{"type":613,"value":694},"Prokaryotic",{"type":613,"value":696}," cells, like those in bacteria, are simpler, lacking a nucleus. Their genetic material floats in a region called the nucleoid.",{"type":608,"tag":609,"props":698,"children":699},{},[700],{"type":613,"value":701},"Despite their simplicity, prokaryotic cells can thrive in extreme environments.",{"title":602,"searchDepth":25,"depth":25,"links":703},[],{"id":66,"data":67,"type":36,"maxContentLevel":19,"version":27,"reviews":70,"parsed":705},{"data":706,"body":708,"toc":768},{"title":602,"description":707},"To understand cell structure, let's think of a cell as a factory with different parts working together.",{"type":605,"children":709},[710,714,726,738,743,755,760],{"type":608,"tag":609,"props":711,"children":712},{},[713],{"type":613,"value":707},{"type":608,"tag":609,"props":715,"children":716},{},[717,719,724],{"type":613,"value":718},"The outer perimeter of this factory is the ",{"type":608,"tag":645,"props":720,"children":721},{},[722],{"type":613,"value":723},"cell membrane",{"type":613,"value":725},": a flexible barrier made mostly of lipids and proteins.",{"type":608,"tag":609,"props":727,"children":728},{},[729,731,736],{"type":613,"value":730},"The membrane is ",{"type":608,"tag":645,"props":732,"children":733},{},[734],{"type":613,"value":735},"selectively permeable",{"type":613,"value":737},", allowing essential materials to enter while keeping harmful elements out, like a gate that only lets in approved visitors and goods.",{"type":608,"tag":609,"props":739,"children":740},{},[741],{"type":613,"value":742},"It also protects the cell and helps it communicate with its surroundings through receptors.",{"type":608,"tag":609,"props":744,"children":745},{},[746,748,753],{"type":613,"value":747},"Inside the cell is the ",{"type":608,"tag":645,"props":749,"children":750},{},[751],{"type":613,"value":752},"cytoplasm",{"type":613,"value":754},", a jelly-like substance (mostly water, with dissolved nutrients, salts, and proteins) that fills the space and surrounds all the cell’s parts.",{"type":608,"tag":609,"props":756,"children":757},{},[758],{"type":613,"value":759},"It's like the factory floor: a workspace of the cell, which provides a medium in which other parts can operate and interact.",{"type":608,"tag":609,"props":761,"children":762},{},[763],{"type":608,"tag":628,"props":764,"children":767},{"alt":630,"src":765,"title":766},"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",[],{"title":602,"searchDepth":25,"depth":25,"links":769},[],{"id":97,"data":98,"type":36,"maxContentLevel":19,"version":25,"reviews":101,"parsed":771},{"data":772,"body":774,"toc":853},{"title":602,"description":773},"In both ​​prokaryotic and eukaryotic cells, you'll find ribosomes on the factory floor (in the cytoplasm). Ribosomes are like tiny assembly machines. They build proteins, following the instructions from the cell’s genetic material.",{"type":605,"children":775},[776,801,806,814,825,845],{"type":608,"tag":609,"props":777,"children":778},{},[779,781,786,788,792,795,799],{"type":613,"value":780},"In both ​​prokaryotic and eukaryotic cells, you'll find ",{"type":608,"tag":645,"props":782,"children":783},{},[784],{"type":613,"value":785},"ribosomes",{"type":613,"value":787}," on the factory floor (in the cytoplasm). ",{"type":608,"tag":789,"props":790,"children":791},"br",{},[],{"type":608,"tag":789,"props":793,"children":794},{},[],{"type":608,"tag":645,"props":796,"children":797},{},[798],{"type":613,"value":120},{"type":613,"value":800}," are like tiny assembly machines. They build proteins, following the instructions from the cell’s genetic material.",{"type":608,"tag":609,"props":802,"children":803},{},[804],{"type":613,"value":805},"In prokaryotic cells (like bacteria), the genetic material and ribosomes float freely in the cytoplasm.",{"type":608,"tag":609,"props":807,"children":808},{},[809],{"type":608,"tag":628,"props":810,"children":813},{"alt":630,"src":811,"title":812},"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",[],{"type":608,"tag":609,"props":815,"children":816},{},[817,819,824],{"type":613,"value":818},"But in eukaryotic cells (like plants and animals), things are more organized. To start with, the genetic material is stored in the ",{"type":608,"tag":645,"props":820,"children":821},{},[822],{"type":613,"value":823},"nucleus",{"type":613,"value":668},{"type":608,"tag":609,"props":826,"children":827},{},[828,830,833,836,838,843],{"type":613,"value":829},"The 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.",{"type":608,"tag":789,"props":831,"children":832},{},[],{"type":608,"tag":789,"props":834,"children":835},{},[],{"type":613,"value":837},"\nThe nucleus is enclosed by a double membrane called the ",{"type":608,"tag":645,"props":839,"children":840},{},[841],{"type":613,"value":842},"nuclear envelope",{"type":613,"value":844},", which protects the DNA while allowing communication with the rest of the cell.",{"type":608,"tag":609,"props":846,"children":847},{},[848],{"type":608,"tag":628,"props":849,"children":852},{"alt":630,"src":850,"title":851},"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",[],{"title":602,"searchDepth":25,"depth":25,"links":854},[],{"id":132,"data":133,"type":36,"maxContentLevel":19,"version":25,"reviews":136,"parsed":856},{"data":857,"body":859,"toc":941},{"title":602,"description":858},"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.",{"type":605,"children":860},[861,873,881,892,905,914,922],{"type":608,"tag":609,"props":862,"children":863},{},[864,866,871],{"type":613,"value":865},"Eukaryotic cells, unlike prokaryotic cells, also have other special parts, called ",{"type":608,"tag":645,"props":867,"children":868},{},[869],{"type":613,"value":870},"organelles",{"type":613,"value":872},", that each do specific jobs. Organelles are like specialized departments in the factory, each handling a specific task.",{"type":608,"tag":609,"props":874,"children":875},{},[876],{"type":608,"tag":628,"props":877,"children":880},{"alt":630,"src":878,"title":879},"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",[],{"type":608,"tag":609,"props":882,"children":883},{},[884,886,891],{"type":613,"value":885},"One of the most important of these organelles is the ",{"type":608,"tag":645,"props":887,"children":888},{},[889],{"type":613,"value":890},"mitochondria",{"type":613,"value":668},{"type":608,"tag":609,"props":893,"children":894},{},[895,897,903],{"type":613,"value":896},"The mitochondria are the power plants of the cell, converting nutrients into usable energy (ATP) through a process known as cellular respiration (—",{"type":608,"tag":898,"props":899,"children":900},"em",{},[901],{"type":613,"value":902},"we will come back to ATP in our section on metabolism",{"type":613,"value":904},").",{"type":608,"tag":609,"props":906,"children":907},{},[908,912],{"type":608,"tag":645,"props":909,"children":910},{},[911],{"type":613,"value":150},{"type":613,"value":913}," are shaped like small capsules or beans and have an outer membrane and a highly folded inner membrane called cristae.",{"type":608,"tag":609,"props":915,"children":916},{},[917],{"type":608,"tag":628,"props":918,"children":921},{"alt":630,"src":919,"title":920},"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",[],{"type":608,"tag":609,"props":923,"children":924},{},[925,927,932,934,939],{"type":613,"value":926},"The ",{"type":608,"tag":645,"props":928,"children":929},{},[930],{"type":613,"value":931},"cristae",{"type":613,"value":933}," increase the ",{"type":608,"tag":645,"props":935,"children":936},{},[937],{"type":613,"value":938},"surface area",{"type":613,"value":940}," where energy production occurs, making the mitochondria highly efficient at generating the energy needed to fuel the cell's processes.",{"title":602,"searchDepth":25,"depth":25,"links":942},[],{"id":174,"data":175,"type":36,"maxContentLevel":19,"version":25,"reviews":178,"parsed":944},{"data":945,"body":947,"toc":1016},{"title":602,"description":946},"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.",{"type":605,"children":948},[949,974,979,987,999,1011],{"type":608,"tag":609,"props":950,"children":951},{},[952,953,958,960,965,967,972],{"type":613,"value":926},{"type":608,"tag":645,"props":954,"children":955},{},[956],{"type":613,"value":957},"endoplasmic reticulum",{"type":613,"value":959}," (ER) is another crucial part of the factory, with two different areas: the ",{"type":608,"tag":645,"props":961,"children":962},{},[963],{"type":613,"value":964},"rough ER",{"type":613,"value":966},", which is covered in ribosomes and helps make and process proteins, and the ",{"type":608,"tag":645,"props":968,"children":969},{},[970],{"type":613,"value":971},"smooth ER",{"type":613,"value":973},", which produces fats and helps detoxify the cell.",{"type":608,"tag":609,"props":975,"children":976},{},[977],{"type":613,"value":978},"It's like having both an assembly line and a quality control department in the same factory.",{"type":608,"tag":609,"props":980,"children":981},{},[982],{"type":608,"tag":628,"props":983,"children":986},{"alt":630,"src":984,"title":985},"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",[],{"type":608,"tag":609,"props":988,"children":989},{},[990,992,997],{"type":613,"value":991},"Once proteins and other materials are made, they move to the ",{"type":608,"tag":645,"props":993,"children":994},{},[995],{"type":613,"value":996},"Golgi apparatus",{"type":613,"value":998},", which packages and sends them to their final destinations, much like a shipping department.",{"type":608,"tag":609,"props":1000,"children":1001},{},[1002,1004,1009],{"type":613,"value":1003},"Some cells, like those in plants, also have ",{"type":608,"tag":645,"props":1005,"children":1006},{},[1007],{"type":613,"value":1008},"chloroplasts",{"type":613,"value":1010},", which capture sunlight and turn it into chemical energy through photosynthesis—imagine them as solar panels powering the factory.",{"type":608,"tag":609,"props":1012,"children":1013},{},[1014],{"type":613,"value":1015},"All these parts work together to keep the cell functioning smoothly.",{"title":602,"searchDepth":25,"depth":25,"links":1017},[],{"id":199,"data":200,"type":25,"version":25,"maxContentLevel":19,"summaryPage":202,"introPage":210,"pages":1019},[1020,1104,1192,1324],{"id":218,"data":219,"type":36,"maxContentLevel":19,"version":25,"reviews":222,"parsed":1021},{"data":1022,"body":1024,"toc":1102},{"title":602,"description":1023},"Reproduction is a key trait of all living things, vital for life to continue across generations.",{"type":605,"children":1025},[1026,1030,1042,1059,1069,1074,1082,1094],{"type":608,"tag":609,"props":1027,"children":1028},{},[1029],{"type":613,"value":1023},{"type":608,"tag":609,"props":1031,"children":1032},{},[1033,1035,1040],{"type":613,"value":1034},"At the cellular level, reproduction is the ",{"type":608,"tag":645,"props":1036,"children":1037},{},[1038],{"type":613,"value":1039},"process by which cells create new cells",{"type":613,"value":1041},", ensuring that organisms grow, repair themselves, and survive through multiple generations.",{"type":608,"tag":609,"props":1043,"children":1044},{},[1045,1047,1052,1053,1058],{"type":613,"value":1046},"There are two main types of reproduction: ",{"type":608,"tag":645,"props":1048,"children":1049},{},[1050],{"type":613,"value":1051},"asexual",{"type":613,"value":661},{"type":608,"tag":645,"props":1054,"children":1055},{},[1056],{"type":613,"value":1057},"sexual",{"type":613,"value":668},{"type":608,"tag":609,"props":1060,"children":1061},{},[1062,1067],{"type":608,"tag":645,"props":1063,"children":1064},{},[1065],{"type":613,"value":1066},"Asexual reproduction",{"type":613,"value":1068}," 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.",{"type":608,"tag":609,"props":1070,"children":1071},{},[1072],{"type":613,"value":1073},"The 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.",{"type":608,"tag":609,"props":1075,"children":1076},{},[1077],{"type":608,"tag":628,"props":1078,"children":1081},{"alt":630,"src":1079,"title":1080},"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",[],{"type":608,"tag":609,"props":1083,"children":1084},{},[1085,1087,1092],{"type":613,"value":1086},"In contrast, ",{"type":608,"tag":645,"props":1088,"children":1089},{},[1090],{"type":613,"value":1091},"sexual reproduction",{"type":613,"value":1093}," involves two parents, resulting in genetically diverse offspring.",{"type":608,"tag":609,"props":1095,"children":1096},{},[1097],{"type":608,"tag":628,"props":1098,"children":1101},{"alt":630,"src":1099,"title":1100},"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",[],{"title":602,"searchDepth":25,"depth":25,"links":1103},[],{"id":261,"data":262,"type":36,"maxContentLevel":19,"version":25,"reviews":265,"parsed":1105},{"data":1106,"body":1108,"toc":1190},{"title":602,"description":1107},"One of the simplest forms of asexual reproduction is binary fission, which is the primary method used by bacteria.",{"type":605,"children":1109},[1110,1128,1140,1145,1153,1165,1177,1185],{"type":608,"tag":609,"props":1111,"children":1112},{},[1113,1115,1119,1121,1126],{"type":613,"value":1114},"One of the simplest forms of ",{"type":608,"tag":645,"props":1116,"children":1117},{},[1118],{"type":613,"value":1051},{"type":613,"value":1120}," ",{"type":608,"tag":645,"props":1122,"children":1123},{},[1124],{"type":613,"value":1125},"reproduction",{"type":613,"value":1127}," is binary fission, which is the primary method used by bacteria.",{"type":608,"tag":609,"props":1129,"children":1130},{},[1131,1133,1138],{"type":613,"value":1132},"In ",{"type":608,"tag":645,"props":1134,"children":1135},{},[1136],{"type":613,"value":1137},"binary fission",{"type":613,"value":1139},", the cell duplicates its genetic material, ensuring that each new cell will have a complete copy of the DNA.",{"type":608,"tag":609,"props":1141,"children":1142},{},[1143],{"type":613,"value":1144},"After 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.",{"type":608,"tag":609,"props":1146,"children":1147},{},[1148],{"type":608,"tag":628,"props":1149,"children":1152},{"alt":630,"src":1150,"title":1151},"image://6756957d-ab2c-4d51-9941-2a92f2450cec","Binary fission (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons",[],{"type":608,"tag":609,"props":1154,"children":1155},{},[1156,1158,1163],{"type":613,"value":1157},"Another example of ",{"type":608,"tag":645,"props":1159,"children":1160},{},[1161],{"type":613,"value":1162},"asexual reproduction",{"type":613,"value":1164}," is budding, observed in organisms like Saccharomyces cerevisiae, a type of yeast.",{"type":608,"tag":609,"props":1166,"children":1167},{},[1168,1170,1175],{"type":613,"value":1169},"During ",{"type":608,"tag":645,"props":1171,"children":1172},{},[1173],{"type":613,"value":1174},"budding",{"type":613,"value":1176},", 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.",{"type":608,"tag":609,"props":1178,"children":1179},{},[1180],{"type":608,"tag":628,"props":1181,"children":1184},{"alt":630,"src":1182,"title":1183},"image://50352fb5-1cb2-4f5a-8533-41c831060f39","S cerevisiae under DIC microscopy, displaying 'budding' in process. (Public domain), via Wikimedia Commons",[],{"type":608,"tag":609,"props":1186,"children":1187},{},[1188],{"type":613,"value":1189},"This method is similar to binary fission but involves the formation of a distinct new cell from the original one.",{"title":602,"searchDepth":25,"depth":25,"links":1191},[],{"id":300,"data":301,"type":36,"maxContentLevel":19,"version":36,"reviews":304,"parsed":1193},{"data":1194,"body":1196,"toc":1322},{"title":602,"description":1195},"Sexual reproduction differs from asexual reproduction because it involves two parents, and the offspring inherit a mix of genetic information from both.",{"type":605,"children":1197},[1198,1208,1220,1232,1244,1269,1277],{"type":608,"tag":609,"props":1199,"children":1200},{},[1201,1206],{"type":608,"tag":645,"props":1202,"children":1203},{},[1204],{"type":613,"value":1205},"Sexual reproduction",{"type":613,"value":1207}," differs from asexual reproduction because it involves two parents, and the offspring inherit a mix of genetic information from both.",{"type":608,"tag":609,"props":1209,"children":1210},{},[1211,1213,1218],{"type":613,"value":1212},"To understand how this works, let's briefly talk about ",{"type":608,"tag":645,"props":1214,"children":1215},{},[1216],{"type":613,"value":1217},"chromosomes",{"type":613,"value":1219},". 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.",{"type":608,"tag":609,"props":1221,"children":1222},{},[1223,1225,1230],{"type":613,"value":1224},"In most of our cells, we have ",{"type":608,"tag":645,"props":1226,"children":1227},{},[1228],{"type":613,"value":1229},"two copies",{"type":613,"value":1231}," of each chromosome—one from each parent.",{"type":608,"tag":609,"props":1233,"children":1234},{},[1235,1237,1242],{"type":613,"value":1236},"In sexual reproduction, however, special cells called ",{"type":608,"tag":645,"props":1238,"children":1239},{},[1240],{"type":613,"value":1241},"gametes",{"type":613,"value":1243}," are involved. In humans and other sexually reproducing organisms, there are two types of gametes:",{"type":608,"tag":1245,"props":1246,"children":1247},"ul",{},[1248,1259],{"type":608,"tag":1249,"props":1250,"children":1251},"li",{},[1252,1257],{"type":608,"tag":645,"props":1253,"children":1254},{},[1255],{"type":613,"value":1256},"Sperm",{"type":613,"value":1258}," (from the father)",{"type":608,"tag":1249,"props":1260,"children":1261},{},[1262,1267],{"type":608,"tag":645,"props":1263,"children":1264},{},[1265],{"type":613,"value":1266},"Egg",{"type":613,"value":1268}," (from the mother)",{"type":608,"tag":609,"props":1270,"children":1271},{},[1272],{"type":608,"tag":628,"props":1273,"children":1276},{"alt":630,"src":1274,"title":1275},"image://21036d7b-8f60-4341-b506-ca9c1b2f1895","Abatus cordatus Female gamete (egg) and male gamete (sperm) (Public domain), via Wikimedia Commons",[],{"type":608,"tag":609,"props":1278,"children":1279},{},[1280,1282,1287,1289,1294,1296,1301,1303,1307,1310,1313,1315,1320],{"type":613,"value":1281},"Each ",{"type":608,"tag":645,"props":1283,"children":1284},{},[1285],{"type":613,"value":1286},"gamete",{"type":613,"value":1288}," carries only ",{"type":608,"tag":645,"props":1290,"children":1291},{},[1292],{"type":613,"value":1293},"one copy",{"type":613,"value":1295}," of each chromosome: half the usual number. For this reason, they're called ",{"type":608,"tag":645,"props":1297,"children":1298},{},[1299],{"type":613,"value":1300},"haploid cells",{"type":613,"value":1302}," (haploid comes from the Greek word \"haploos,\" which means \"single\")",{"type":608,"tag":645,"props":1304,"children":1305},{},[1306],{"type":613,"value":668},{"type":608,"tag":789,"props":1308,"children":1309},{},[],{"type":608,"tag":789,"props":1311,"children":1312},{},[],{"type":613,"value":1314},"\nThe process that creates gametes is called ",{"type":608,"tag":645,"props":1316,"children":1317},{},[1318],{"type":613,"value":1319},"meiosis",{"type":613,"value":1321},", a type of cell division in which the number of chromosomes is reduced by half.",{"title":602,"searchDepth":25,"depth":25,"links":1323},[],{"id":330,"data":331,"type":36,"maxContentLevel":19,"version":36,"reviews":334,"parsed":1325},{"data":1326,"body":1328,"toc":1385},{"title":602,"description":1327},"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.",{"type":605,"children":1329},[1330,1334,1344,1362,1367,1375,1380],{"type":608,"tag":609,"props":1331,"children":1332},{},[1333],{"type":613,"value":1327},{"type":608,"tag":609,"props":1335,"children":1336},{},[1337,1339,1343],{"type":613,"value":1338},"This new type of cell, created from the fusion of two gametes, is called a ",{"type":608,"tag":645,"props":1340,"children":1341},{},[1342],{"type":613,"value":341},{"type":613,"value":668},{"type":608,"tag":609,"props":1345,"children":1346},{},[1347,1349,1353,1355,1360],{"type":613,"value":1348},"Since the ",{"type":608,"tag":645,"props":1350,"children":1351},{},[1352],{"type":613,"value":341},{"type":613,"value":1354}," contains a complete set of chromosomes (two sets: one from each parent) it's known as a ",{"type":608,"tag":645,"props":1356,"children":1357},{},[1358],{"type":613,"value":1359},"diploid cell",{"type":613,"value":1361},", from the Greek word \"diploos,\" meaning \"double\".",{"type":608,"tag":609,"props":1363,"children":1364},{},[1365],{"type":613,"value":1366},"Diploid cells contain the full genetic blueprint for the new organism.",{"type":608,"tag":609,"props":1368,"children":1369},{},[1370],{"type":608,"tag":628,"props":1371,"children":1374},{"alt":630,"src":1372,"title":1373},"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",[],{"type":608,"tag":609,"props":1376,"children":1377},{},[1378],{"type":613,"value":1379},"Unlike asexual reproduction, where the offspring are clones of the parent, sexual reproduction shuffles the genetic deck, leading to offspring with different combinations of traits.",{"type":608,"tag":609,"props":1381,"children":1382},{},[1383],{"type":613,"value":1384},"This 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.",{"title":602,"searchDepth":25,"depth":25,"links":1386},[],{"id":364,"data":365,"type":25,"version":19,"maxContentLevel":19,"summaryPage":367,"introPage":375,"pages":1388,"reviews":501},[1389,1475,1543,1649],{"id":383,"data":384,"type":36,"maxContentLevel":19,"version":25,"reviews":387,"parsed":1390},{"data":1391,"body":1393,"toc":1473},{"title":602,"description":1392},"Growth and development are fundamental processes that characterize all living organisms, enabling them to survive, reproduce, and adapt in a continuously changing environment.",{"type":605,"children":1394},[1395,1405,1416,1440,1448,1453],{"type":608,"tag":609,"props":1396,"children":1397},{},[1398,1403],{"type":608,"tag":645,"props":1399,"children":1400},{},[1401],{"type":613,"value":1402},"Growth and development",{"type":613,"value":1404}," are fundamental processes that characterize all living organisms, enabling them to survive, reproduce, and adapt in a continuously changing environment.",{"type":608,"tag":609,"props":1406,"children":1407},{},[1408,1410,1414],{"type":613,"value":1409},"As we saw in the previous orb (",{"type":608,"tag":645,"props":1411,"children":1412},{},[1413],{"type":613,"value":1125},{"type":613,"value":1415},"), this process begins with a single cell, whether through the fusion of gametes in sexual reproduction or other means of asexual reproduction.",{"type":608,"tag":609,"props":1417,"children":1418},{},[1419,1420,1425,1427,1432,1434,1438],{"type":613,"value":1132},{"type":608,"tag":645,"props":1421,"children":1422},{},[1423],{"type":613,"value":1424},"single-celled organisms",{"type":613,"value":1426}," like bacteria, growth primarily involves increasing in size, followed by division. For example, the bacterium ",{"type":608,"tag":645,"props":1428,"children":1429},{},[1430],{"type":613,"value":1431},"Escherichia coli (E. coli)",{"type":613,"value":1433}," grows from about 1–2 micrometers to 3–4 micrometers before dividing into two new cells through ",{"type":608,"tag":645,"props":1435,"children":1436},{},[1437],{"type":613,"value":1137},{"type":613,"value":1439},", a simple asexual reproduction process.",{"type":608,"tag":609,"props":1441,"children":1442},{},[1443],{"type":608,"tag":628,"props":1444,"children":1447},{"alt":630,"src":1445,"title":1446},"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",[],{"type":608,"tag":609,"props":1449,"children":1450},{},[1451],{"type":613,"value":1452},"Under favorable conditions, E. coli can double in number every 20 minutes, leading to rapid population growth.",{"type":608,"tag":609,"props":1454,"children":1455},{},[1456,1458,1463,1465,1468,1471],{"type":613,"value":1457},"For ",{"type":608,"tag":645,"props":1459,"children":1460},{},[1461],{"type":613,"value":1462},"multicellular organisms",{"type":613,"value":1464},", 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.",{"type":608,"tag":789,"props":1466,"children":1467},{},[],{"type":608,"tag":789,"props":1469,"children":1470},{},[],{"type":613,"value":1472},"\nThis orb will examine these processes.",{"title":602,"searchDepth":25,"depth":25,"links":1474},[],{"id":408,"data":409,"type":36,"maxContentLevel":19,"version":25,"reviews":412,"parsed":1476},{"data":1477,"body":1479,"toc":1541},{"title":602,"description":1478},"Development refers to the changes that occur as cells progress through their life cycle.",{"type":605,"children":1480},[1481,1491,1508,1516,1521,1526,1536],{"type":608,"tag":609,"props":1482,"children":1483},{},[1484,1489],{"type":608,"tag":645,"props":1485,"children":1486},{},[1487],{"type":613,"value":1488},"Development",{"type":613,"value":1490}," refers to the changes that occur as cells progress through their life cycle.",{"type":608,"tag":609,"props":1492,"children":1493},{},[1494,1495,1499,1501,1506],{"type":613,"value":1132},{"type":608,"tag":645,"props":1496,"children":1497},{},[1498],{"type":613,"value":1462},{"type":613,"value":1500},", development relies on ",{"type":608,"tag":645,"props":1502,"children":1503},{},[1504],{"type":613,"value":1505},"cell differentiation",{"type":613,"value":1507},", where unspecialized cells evolve into specialized cell types with distinct structures and functions.",{"type":608,"tag":609,"props":1509,"children":1510},{},[1511],{"type":608,"tag":628,"props":1512,"children":1515},{"alt":630,"src":1513,"title":1514},"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",[],{"type":608,"tag":609,"props":1517,"children":1518},{},[1519],{"type":613,"value":1520},"This differentiation allows organisms to efficiently address environmental challenges and opportunities.",{"type":608,"tag":609,"props":1522,"children":1523},{},[1524],{"type":613,"value":1525},"For 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.",{"type":608,"tag":609,"props":1527,"children":1528},{},[1529,1534],{"type":608,"tag":645,"props":1530,"children":1531},{},[1532],{"type":613,"value":1533},"Stem cells",{"type":613,"value":1535}," 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.",{"type":608,"tag":609,"props":1537,"children":1538},{},[1539],{"type":613,"value":1540},"These processes are directed by an organism’s genetic code and influenced by environmental factors.",{"title":602,"searchDepth":25,"depth":25,"links":1542},[],{"id":447,"data":448,"type":36,"maxContentLevel":19,"version":25,"reviews":451,"parsed":1544},{"data":1545,"body":1547,"toc":1647},{"title":602,"description":1546},"In multicellular organisms, growth occurs through an increase in the number of cells.",{"type":605,"children":1548},[1549,1559,1590,1602,1611,1619,1630,1635],{"type":608,"tag":609,"props":1550,"children":1551},{},[1552,1553,1557],{"type":613,"value":1132},{"type":608,"tag":645,"props":1554,"children":1555},{},[1556],{"type":613,"value":1462},{"type":613,"value":1558},", growth occurs through an increase in the number of cells.",{"type":608,"tag":609,"props":1560,"children":1561},{},[1562,1564,1569,1571,1575,1577,1582,1584,1589],{"type":613,"value":1563},"While ",{"type":608,"tag":645,"props":1565,"children":1566},{},[1567],{"type":613,"value":1568},"prokaryotes",{"type":613,"value":1570}," like bacteria commonly replicate via ",{"type":608,"tag":645,"props":1572,"children":1573},{},[1574],{"type":613,"value":1137},{"type":613,"value":1576},", a simpler process where the cell duplicates its DNA and splits, ",{"type":608,"tag":645,"props":1578,"children":1579},{},[1580],{"type":613,"value":1581},"eukaryotic cells",{"type":613,"value":1583}," undergo a more complex division called ",{"type":608,"tag":645,"props":1585,"children":1586},{},[1587],{"type":613,"value":1588},"mitosis",{"type":613,"value":668},{"type":608,"tag":609,"props":1591,"children":1592},{},[1593,1595,1600],{"type":613,"value":1594},"In eukaryotes, cell growth is regulated by the ",{"type":608,"tag":645,"props":1596,"children":1597},{},[1598],{"type":613,"value":1599},"cell cycle",{"type":613,"value":1601},", which includes phases of growth, DNA replication, and division.",{"type":608,"tag":609,"props":1603,"children":1604},{},[1605,1609],{"type":608,"tag":645,"props":1606,"children":1607},{},[1608],{"type":613,"value":399},{"type":613,"value":1610}," ensures that all necessary components, including DNA and organelles, are correctly divided between two new daughter cells.",{"type":608,"tag":609,"props":1612,"children":1613},{},[1614],{"type":608,"tag":628,"props":1615,"children":1618},{"alt":630,"src":1616,"title":1617},"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",[],{"type":608,"tag":609,"props":1620,"children":1621},{},[1622,1624,1628],{"type":613,"value":1623},"Unlike binary fission, which occurs in cells without a nucleus (procaryotic cells) mitosis involves the division of the ",{"type":608,"tag":645,"props":1625,"children":1626},{},[1627],{"type":613,"value":823},{"type":613,"value":1629},", followed by the rest of the cell, ensuring genetic consistency and functionality in multicellular organisms.",{"type":608,"tag":609,"props":1631,"children":1632},{},[1633],{"type":613,"value":1634},"Mitosis plays a critical role in growth and tissue repair in multicellular organisms like plants and animals, where cells need constant replacement.",{"type":608,"tag":609,"props":1636,"children":1637},{},[1638,1640,1645],{"type":613,"value":1639},"Some unicellular ",{"type":608,"tag":645,"props":1641,"children":1642},{},[1643],{"type":613,"value":1644},"eukaryotes",{"type":613,"value":1646},", such as certain protists and fungi, also reproduce asexually using mitosis.",{"title":602,"searchDepth":25,"depth":25,"links":1648},[],{"id":485,"data":486,"type":36,"maxContentLevel":19,"version":36,"reviews":489,"parsed":1650},{"data":1651,"body":1653,"toc":1700},{"title":602,"description":1652},"In some organisms, development involves dramatic transformations, such as metamorphosis. A well-known example is the transition of a caterpillar into a butterfly.",{"type":605,"children":1654},[1655,1667,1675,1685,1690,1695],{"type":608,"tag":609,"props":1656,"children":1657},{},[1658,1660,1665],{"type":613,"value":1659},"In some organisms, development involves dramatic transformations, such as ",{"type":608,"tag":645,"props":1661,"children":1662},{},[1663],{"type":613,"value":1664},"metamorphosis",{"type":613,"value":1666},". A well-known example is the transition of a caterpillar into a butterfly.",{"type":608,"tag":609,"props":1668,"children":1669},{},[1670],{"type":608,"tag":628,"props":1671,"children":1674},{"alt":630,"src":1672,"title":1673},"image://e2103ae1-ee5e-49ed-8faf-98084e3faa8b","Metamorphosis of the Lappet moth (Public domain), via Wikimedia Commons",[],{"type":608,"tag":609,"props":1676,"children":1677},{},[1678,1679,1683],{"type":613,"value":1169},{"type":608,"tag":645,"props":1680,"children":1681},{},[1682],{"type":613,"value":1664},{"type":613,"value":1684},", 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.",{"type":608,"tag":609,"props":1686,"children":1687},{},[1688],{"type":613,"value":1689},"Many 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.",{"type":608,"tag":609,"props":1691,"children":1692},{},[1693],{"type":613,"value":1694},"In 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.",{"type":608,"tag":609,"props":1696,"children":1697},{},[1698],{"type":613,"value":1699},"Over 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.",{"title":602,"searchDepth":25,"depth":25,"links":1701},[],{"id":513,"data":514,"type":25,"version":27,"maxContentLevel":19,"summaryPage":516,"introPage":524,"pages":1703},[1704,1770,1833],{"id":532,"data":533,"type":36,"maxContentLevel":19,"version":36,"reviews":536,"parsed":1705},{"data":1706,"body":1708,"toc":1768},{"title":602,"description":1707},"Adaptation is a fundamental concept in biology that explains how organisms evolve over generations to better survive and reproduce in their environments.",{"type":605,"children":1709},[1710,1719,1724,1732,1758,1763],{"type":608,"tag":609,"props":1711,"children":1712},{},[1713,1717],{"type":608,"tag":645,"props":1714,"children":1715},{},[1716],{"type":613,"value":551},{"type":613,"value":1718}," is a fundamental concept in biology that explains how organisms evolve over generations to better survive and reproduce in their environments.",{"type":608,"tag":609,"props":1720,"children":1721},{},[1722],{"type":613,"value":1723},"This process is driven by the natural selection of advantageous traits, which are characteristics that increase an organism's chances of survival and reproduction.",{"type":608,"tag":609,"props":1725,"children":1726},{},[1727],{"type":608,"tag":628,"props":1728,"children":1731},{"alt":630,"src":1729,"title":1730},"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",[],{"type":608,"tag":609,"props":1733,"children":1734},{},[1735,1737,1742,1744,1749,1751,1756],{"type":613,"value":1736},"These traits can be ",{"type":608,"tag":645,"props":1738,"children":1739},{},[1740],{"type":613,"value":1741},"behavioral",{"type":613,"value":1743},", ",{"type":608,"tag":645,"props":1745,"children":1746},{},[1747],{"type":613,"value":1748},"physiological",{"type":613,"value":1750},", or ",{"type":608,"tag":645,"props":1752,"children":1753},{},[1754],{"type":613,"value":1755},"structural",{"type":613,"value":1757},", and they develop over many generations.",{"type":608,"tag":609,"props":1759,"children":1760},{},[1761],{"type":613,"value":1762},"Behavioral 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.",{"type":608,"tag":609,"props":1764,"children":1765},{},[1766],{"type":613,"value":1767},"This 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.",{"title":602,"searchDepth":25,"depth":25,"links":1769},[],{"id":553,"data":554,"type":36,"maxContentLevel":19,"version":25,"reviews":557,"parsed":1771},{"data":1772,"body":1774,"toc":1831},{"title":602,"description":1773},"Physiological adaptations involve changes in an organism's internal functions to cope with environmental challenges.",{"type":605,"children":1775},[1776,1786,1791,1801,1813,1821,1826],{"type":608,"tag":609,"props":1777,"children":1778},{},[1779,1784],{"type":608,"tag":645,"props":1780,"children":1781},{},[1782],{"type":613,"value":1783},"Physiological adaptations",{"type":613,"value":1785}," involve changes in an organism's internal functions to cope with environmental challenges.",{"type":608,"tag":609,"props":1787,"children":1788},{},[1789],{"type":613,"value":1790},"For 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.",{"type":608,"tag":609,"props":1792,"children":1793},{},[1794,1799],{"type":608,"tag":645,"props":1795,"children":1796},{},[1797],{"type":613,"value":1798},"Structural adaptations",{"type":613,"value":1800}," are physical features of an organism that help it survive.",{"type":608,"tag":609,"props":1802,"children":1803},{},[1804,1806,1811],{"type":613,"value":1805},"The 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 ",{"type":608,"tag":645,"props":1807,"children":1808},{},[1809],{"type":613,"value":1810},"webbed feet",{"type":613,"value":1812},", which provide a larger surface area to push against water, making them better adapted for swimming in their aquatic environments.",{"type":608,"tag":609,"props":1814,"children":1815},{},[1816],{"type":608,"tag":628,"props":1817,"children":1820},{"alt":630,"src":1818,"title":1819},"image://44333297-614d-458c-8a22-e8ca18cc2819","Labuť, nohy (swan, feet) (Public domain), via Wikimedia Commons",[],{"type":608,"tag":609,"props":1822,"children":1823},{},[1824],{"type":613,"value":1825},"Adaptations are not always perfect. They represent compromises or trade-offs that enhance survival and reproduction in specific environments.",{"type":608,"tag":609,"props":1827,"children":1828},{},[1829],{"type":613,"value":1830},"For 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.",{"title":602,"searchDepth":25,"depth":25,"links":1832},[],{"id":573,"data":574,"type":36,"maxContentLevel":19,"version":19,"reviews":577,"parsed":1834},{"data":1835,"body":1837,"toc":1887},{"title":602,"description":1836},"Adaptations result from the genetic variation within a population.",{"type":605,"children":1838},[1839,1851,1856,1861,1866],{"type":608,"tag":609,"props":1840,"children":1841},{},[1842,1844,1849],{"type":613,"value":1843},"Adaptations result from the ",{"type":608,"tag":645,"props":1845,"children":1846},{},[1847],{"type":613,"value":1848},"genetic variation",{"type":613,"value":1850}," within a population.",{"type":608,"tag":609,"props":1852,"children":1853},{},[1854],{"type":613,"value":1855},"When 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.",{"type":608,"tag":609,"props":1857,"children":1858},{},[1859],{"type":613,"value":1860},"Over time, the frequency of these traits increases in the population, leading to adaptation.",{"type":608,"tag":609,"props":1862,"children":1863},{},[1864],{"type":613,"value":1865},"The 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.",{"type":608,"tag":609,"props":1867,"children":1868},{},[1869,1871,1875,1876,1880,1881,1885],{"type":613,"value":1870},"In summary, adaptation is a key mechanism by which life on Earth evolves in response to changing environments. These adaptations can be ",{"type":608,"tag":645,"props":1872,"children":1873},{},[1874],{"type":613,"value":1741},{"type":613,"value":1743},{"type":608,"tag":645,"props":1877,"children":1878},{},[1879],{"type":613,"value":1748},{"type":613,"value":1750},{"type":608,"tag":645,"props":1882,"children":1883},{},[1884],{"type":613,"value":1755},{"type":613,"value":1886},", and they are passed down through generations, leading to a diversity of life forms.",{"title":602,"searchDepth":25,"depth":25,"links":1888},[],{"left":4,"top":4,"width":1890,"height":1890,"rotate":4,"vFlip":6,"hFlip":6,"body":1891},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":1890,"height":1890,"rotate":4,"vFlip":6,"hFlip":6,"body":1893},"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"M4 5h16M4 12h16M4 19h16\"/>",1778224898713]