Ap Biology Chapter 1 Summary

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AP Biology Chapter 27 Lecture Notes Prokaryotes and the Origins of Metabolic Diversity I. The World of Prokaryotes A. They’re (almost) everywhere! An overview of prokaryotic life 1. Prokaryotes dominate the biosphere. Their biomass is at least 10 times greater than all eukaryotes. You have more prokaryotes in your mouth or on your skin than the total number of humans who have ever lived. They are found wherever there is life and in places too extreme for any eukaryote. They can cause disease, give us vitamins, cycle carbon and nitrogen. Life on Earth as we know it would stop without them. Eukaryotes cannot exist without them but they can exist without eukaryotes. 2. They often live in symbiosis with each other and with eukaryotes, e.g.,…show more content…
During transformation, a prokaryotic cell takes up genes from the surrounding environment. In conjugation genes are transferred directly from one organism to another. In transduction, viruses transfer genes between prokaryotes. Mutation is the major source of genetic variation in prokaryotes. Because some bacteria can divide every twenty minutes, a new beneficial mutation can spread rapidly through prokaryotic populations in response to environmental changes. 2. Prokaryotic growth refers more to the multiplication of cells, rather than the increase in size. Various species of prokaryotes are adapted to various conditions. Refrigeration slows food spoilage because the lower temperature slows binary fission. Under optimal conditions with no limiting factors prokaryotes can grow exponentially. 3. Some bacteria can form endospores in response to harsh environmental conditions. An endospore is a chromosome surrounded by a durable wall that can resist desiccation, freezing and boiling water. They can be destroyed by pressure cookers, e.g., autoclaves that heat them in steam at 120 degrees. 4. Many microorganisms, including protists, bacteria and fungi, can release antibiotics to kill or inhibit the growth of other microorganisms. III. Nutritional and Metabolic Diversity A. Metabolic diversity is greater among prokaryotes than among all eukaryotes combined. B. Prokaryotes can be grouped…show more content…
The Ecological Impact of Prokaryotes A. Prokaryotes are indispensable links in the recycling of chemical elements in ecosystems 1. Prokaryotes play essential roles in Earth’s biogeochemical cycles, e.g., decomposers break down and recycle organic compounds in dead organisms. Autotrophs make organic compounds that form the foundation for many food webs. They can metabolize inorganic molecules, make oxygen for the atmosphere, and fix nitrogen that becomes a nitrogen source for amino acids and nucleic acids. B. Many prokaryotes are symbiotic 1. In symbiosis, organisms of two different species are in direct contact. The larger is called the host. In mutualism both species benefit; in commensalism one species benefits and the other is not affected; and in parasitism the parasite benefits and harms the host. 2. Prokaryotes engage in all three types of symbiosis with eukaryotes, e.g., Rhizobium is mutualistic with plants, bacteria living within the intestines and on the skin of humans are mostly commensal but some are mutualistic, e.g., anaerobic, fermenting, bacteria living within the female vagina create an acidic environment hostile to yeast and other fungi. C. Pathogenic prokaryotes cause many human diseases 1. To be pathogenic, a parasite must invade the host, resist internal defenses long enough to begin growing, then harm the host in some way. Pathogenic prokaryotes cause about half of all human diseases. Opportunistic pathogens

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