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CHAPTER 21 - CHAPTER 21 THE ORIGIN AND AVOLUTIONARY HISTORY...

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CHAPTER 21 THE ORIGIN AND AVOLUTIONARY HISTORY OF LIFE Chemical evolution o The process by which life developed from nonliving matter CHEMICAL EVOLUTION ON EARLY EARTH Organic molecules formed on primitive Earth Prebiotic soup hypothesis o Proposes that the organic precursors of life formed near the earth’s surface Iron-sulfur world hypothesis o Proposes that organic precursors of life formed at cracks in the ocean’s floor Organic molecules may have been produced at Earth’s surface Organic molecules may have formed at hydrothermal vents Hydrothermal vents o Cracks in the deep-ocean floor where hot water, carbon monoxide, and minerals such as sulfides of iron and nickel spew forth THE FIRST CELLS Protobionts o Assemblages of abiotically produced organic polymers Microspheres o A type of protobiont formed by adding water to abiotically formed polypeptides Molecular reproduction was a crucial step in the origin of cells RNA world o A model that says the chemistry of prebiotic earth gave rise to self- replicating RNA molecules that functioned as both enzymes and substrates for their own replication Ribozymes o RNA that functions as an enzyme In Vitro evolution – directed evolution
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