Chapter 5 Book Notes

Life is something that can reproduce and evolve

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Life is something that can reproduce and evolve through natural selection Some type of chemical evolution Conclusion: The ability to produce and evolve through natural selection seems likely to be shared by most life in the universe What are living cells? All living organisms are made of cells, or microscopic units in which the living matter inside is separated from the outside world by a barrier called a membrane Basic structures of life on Earth All cells pass hereditary info in the same basic way with DNA and same chemical processes All life on Earth shares a common ancestor Most of life is made from oxygen, carbon, hydrogen, and nitrogen alone (96%) Most of the oxygen in living cells is actually part of water molecules Molecules that account for a cell’s structure and function are due to CARBON
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All life on earth is carbon-based and carbon is important because it can combine with other elements to make complex molecules (chemical bonds) Carbon can bond to as many as four atoms at a time; carbon molecules – organic molecules Silicon is the only element besides carbon that can have four bonds at once. However, they are weaker, form single bonds most of the time, and cannot be mobile in the environment in the form of gaseous carbon dioxide Conclusion: Carbon-based molecules are even found in space, which suggests that carbon chemistry is so easy and so common that even if life with another basis were possible, carbon-based life probably would arise first and then reproduce so successfully. What are the molecular components of cells? Carbohydrates, lipids, proteins, and nucleic acids All proteins are large molecules built from long chains of amino acids Amino acids – handedness RNA caries out instructions contained in DNA Conclusion: Commonalities between the molecules used in different organisms, such as the fact that all life on earth is L-handed, provide evidence that all life evolved from a common ancestor.
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