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Ck 12: Life Science: Role of Amphibians
[Free Registration/Login may be required to access all resource tools.] Humans have used amphibians for a number of purposes for thousands of years, if not longer. Amphibians play significant roles in many food webs and are thus an...
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Ck 12: Life Science: Amphibians
[Free Registration/Login may be required to access all resource tools.] Amphibians are a group of vertebrates that have adapted to live in both water and on land. Amphibian larvae are born and live in water, and they breathe using gills....
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Ck 12: Life Science: Archaea
[Free Registration/Login may be required to access all resource tools.] For many years, archaea were classified as bacteria. Like the bacteria, archaea lacked a nucleus and membrane-bound organelles and, therefore, were prokaryotic...
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Ck 12: Life Science: Autoimmune Diseases
[Free Registration/Login may be required to access all resource tools.] The immune system usually protects you from pathogens and other causes of disease. When the immune system is working properly, it keeps you from getting sick. But...
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Ck 12: Life Science: Bacteria in the Digestive System
[Free Registration/Login may be required to access all resource tools.] Yogurt is a good source of calcium. Yogurt also contains active cultures of "good" bacteria. Foods that contain these beneficial bacteria are sometimes called...
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Ck 12: Life Science: Bacteria Reproduction
[Free Registration/Login may be required to access all resource tools.] Bacteria, being single-celled prokaryotic organisms, do not have a male or female version. Bacteria reproduce asexually. In asexual reproduction, the "parent"...
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Ck 12: Life Science: B and T Cell Response
[Free Registration/Login may be required to access all resource tools.] Some defenses, like your skin and mucous membranes, are not designed to ward off a specific pathogen. They are just general defenders against disease. Your body also...
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Ck 12: Life Science: Biotechnology in Agriculture
[Free Registration/Login may be required to access all resource tools.] The majority of the corn in the United States is genetically engineered. Corn syrup is used to sweeten many things, like Coke. Corn is also fed to the cows. Learn...
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Ck 12: Life Science: Cartilaginous Fish
[Free Registration/Login may be required to access all resource tools.] Cartilaginous fish range in size from the dwarf lanternshark, at 6.3 inches, to the 50-foot whale shark. These fish have a jaw and evolved from the jawless fish....
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Ck 12: Life Science: Light Reactions of Photosynthesis
[Free Registration/Login may be required to access all resource tools.] Although we generally discuss plants when learning about photosynthesis, keep in mind that plants are not the only organisms that can make their own food. Some...
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Ck 12: Life Science: Meiosis
[Free Registration/Login may be required to access all resource tools.] Sexual reproduction combines gametes from two parents. Gametes are produced by a special type of cell division known as meiosis. Meiosis contains two rounds of cell...
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Ck 12: Life Science: Microevolution and Macroevolution
[Free Registration/Login may be required to access all resource tools.] Does evolution only happen gradually through small changes? Or is it possible that drastic environmental changes can cause new species to evolve? Or can both small...
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Ck 12: Life Science: Mollusks
[Free Registration/Login may be required to access all resource tools.] Mollusks are invertebrates that usually have a hard shell, a mantle, and a radula. Learn more about mollusks in this learning module produced by CK-12.
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Ck 12: Life Science: Nonvascular Plants
[Free Registration/Login may be required to access all resource tools.] Nonvascular seedless plants lack vascular tissue and they do not have true roots, stems, or leaves, but they can have stem-like and root-like structures. These...
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Ck 12: Life Science: Organization of the Human Body
[Free Registration/Login may be required to access all resource tools.] Cells, like these nerve cells, do not work in isolation. To send orders from your brain to your legs, for example, signals pass through many nerve cells. These cells...
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Ck 12: Life Science: Origin of Species
[Free Registration/Login may be required to access all resource tools.] The creation of a new species is called speciation. Most new species develop naturally. But humans have also artificially created new breeds and species for...
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Ck 12: Life Science: Outdoor Air Pollution
[Free Registration/Login may be required to access all resource tools.] Air pollution is due to chemical substances and particles released into the air mainly by human actions. This pollution affects entire ecosystems around the world....
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Ck 12: Life Science: Plant Like Protists
[Free Registration/Login may be required to access all resource tools.] Plant-like protists are known as algae. They are a large and diverse group. Plant-like protists are autotrophs. This means that they produce their own food. They...
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Ck 12: Life Science: Pregnancy and Childbirth
[Free Registration/Login may be required to access all resource tools.] While a woman is pregnant, the developing baby may be called an embryo or a fetus. The embryo stage lasts until the end of the 8th week after fertilization. After...
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Ck 12: Life Science: Preventing Noninfectious Diseases
[Free Registration/Login may be required to access all resource tools.] Most allergies can be prevented by avoiding the substances that cause them. For example, you can avoid pollens by staying indoors as much as possible. You can learn...
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Ck 12: Life Science: Primates
[Free Registration/Login may be required to access all resource tools.] If primates are mammals, what makes them seem so different from most mammals? Primates, including humans, have several unique features. Some adaptations give...
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Ck 12: Life Science: Protist Characteristics
[Free Registration/Login may be required to access all resource tools.] Protists are eukaryotes, which means their cells have a nucleus and other membrane-bound organelles. Most protists are single-celled. Other than these features, they...
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Ck 12: Life Science: Protists Nutrition
[Free Registration/Login may be required to access all resource tools.] The cells of protists need to perform all of the functions that other cells do, such as grow and reproduce, maintain homeostasis, and obtain energy. They also need...
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Ck 12: Life Science: Reptiles
[Free Registration/Login may be required to access all resource tools.] What reptiles can you name? Snakes, alligators, and crocodiles are all reptiles. Modern reptiles live on every continent except Antarctica. They range in size from...