BIOL 1202 Chapter : Chapter 25
Document Summary
Early earth: earth is about 4. 6 billion years old. Radiometric dating of meteorites and moon rocks: life arose about 3. 8 billion years ago. Chemical traces in rocks 3. 8 billion years. Fossil bacteria in rocks 3. 5 billion years: no spontaneous generation now, but must have happened then. No free oxygen: abundant energy to drive reactions. Uv light from the sun: testable hypotheses explaining the origin of life, abiotic synthesis of small organic molecules, joining these molecules into polymers, packaging these molecules into protobionts , the origin of self-replicating molecules. Alternative hypotheses: first organic compounds may have been synthesized near hydrothermal vents, extraterrestrial origin. ^all of these probably contributed to some degree. Abiotic synthesis of polymers: small organic molecules polymerize when they are concentrated on hot sand or clay. Protobionts: aggregates of abiotically produced molecules surrounded by a membrane, liposomes can form when lipids or other organic molecules are added to water. Now: dna>rna>protein, needs proteins to synthesize more dna.
