Chapter 25

Chapter 25 - 19:11 Chapter25: EarlyEarth o...

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19:11 Chapter 25: The History of Life on Earth Early Earth o Earth is about 4.6 billion years (BY) old o Life arose about 3.8 BY ago Chemical traces in rocks 3.8 BY Fossil bacteria in rocks 3.5 BY o No spontaneous generation now, but must have happened then Conditions on Early Earth o Atmosphere C02; CH4; NH3; H2S; H2O No free oxygen o Abundant energy to drive reactions Frequent storms with much lightening Frequent volcanic eruptions Frequent meteor impacts UV light form the sun Life on Earth arose as a result of physical chemical processes.   is a  scientific theory Life is so complex that is must have been created by a supernatural  being.   not a scientific theory (can be tested, observed, evidence) Testable hypotheses explaining the origin of life o 1. Abiotic synthesis of small organic molecules o 2. Joining these molecules into polymers o 3. Packaging these molecules into “protobionts” o 4. The origin of self-replicating molecules Miller & Urey Experiments
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o Figure 4.2 Alternative Hypotheses o 1. First organic compounds may have been synthesized near hydrothermal 
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This note was uploaded on 02/22/2010 for the course BIOL 1202 taught by Professor Gregg during the Spring '08 term at LSU.

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Chapter 25 - 19:11 Chapter25: EarlyEarth o...

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