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Unformatted text preview: CHAPTER 25 Early Earth • Earth is about 4.6 billion years old o Radiometric dating of meteorites and moon rocks • Life arose about 3.8 billion years ago o Chemical traces in rocks 3.8 billion years ago -- Fossil bacteria in rocks 3.5 billion years ago • No spontaneous generation now, but must have happened then Conditions on Early Earth • Atmosphere o CO2, CH4, NH3, H2S, H2O o No free oxygen • Abundant energy to drive reactions o Frequent storms with much lightening o Frequent volcanic eruptions o frequent meteor impacts o no oxygen = no ozone = UV light from the sun o CQ Is the following statement a scientific theory? Life on Earth arose as a result of physical – chemical processes.A: Yes Is this a scientific theory? Life is so complex that it must have been created by a supernatural being. A: NO Testable hypotheses explaining the origin of life 1. Abiotic synthesis of small organic molecules 2. Joining these molecules into polymers 3. Packaging these molecules into “protobionts” 4. The origin of self- replicating molecules Miller& Urey experiments Set up airtight apparatus and put gases similar to gases in early atmosphere and boiled water to get water vapor.Let it run for a few weeks.Set up airtight apparatus and put gases similar to gases in early atmosphere and boiled water to get water vapor....
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