Chapter 25- History of Life on Earth

Chapter 25- History of Life on Earth - Chapter 25 History...

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Chapter 25 History of Life on Earth! (hypothesis bases, not a theory) How did Life Begin?? A few centuries ago: 1. People thought that new living things appeared all of the time Spontaneous Generation Refuted Mid 1800s Louis Pasteur - Broth I flask is boiled to kill preexisting microorganisms As broth cools, condensed water collects, sealing the mouth of the flask If neck is later broken off, outside air can carry microorganisms into broth This experiment lead to the belief that spontaneous generation does not occur Conditions on Early Earth: Atmosphere: 1. CO2, CH4, NH3, H2, N2, HCL, H2S, H2O (similar to Jupiter today) 2. No free oxygen 3. Frequent storms with lots of lightning 4. Frequent volcanic corruptions 5. Frequent meteor impacts 6. UV light from the sun (this could cause mutations in cells and help life forms survive better) 7. No ozone layer ** pretty much there was no oxygen in the atmosphere back then*** Earth before life Arose: Earth is about 4.6 billion years old o Radiometric dating of meteorites and moon rocks Life arose about 3.8 billion years ago
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o Chemical traces in rocks 3.8 Billion years o Fossil bacteria in rocks 3.5 billion years o Prokaryotes were the first type of life found on earth o No spontaneous generation now, but must have happened then Rate of Decay of 40 K to 40 Ar Unit of half life- years Potassium 40 naturally decays to argon 40 Rock melts and goes off as a gas As the rock forms, potassium 40 is at a high level You can measure amounts of K 40 in a rock with a standard curve The Experiment of Miller and Urey Set up an experiment to try to produce life. Tried to mimic early atmosphere, contained the gases that were present (list up in notes) They are going to supply water vapor This experiment does not work They noticed that as the water was turning brown, organic molecules started to appear after only a few days, the building blocks of life Hypothesis states that by chance, Spontaneous generation occurs How to assemble a living thing: 1. Accumulation of organic molecules 2. Catalyze reaction—something to speed up the reaction (enzymes and ribosomal RNA) 3. Reproduce from stored genetic info
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This note was uploaded on 02/05/2011 for the course BIOL 1202 taught by Professor Gregg during the Spring '08 term at LSU.

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Chapter 25- History of Life on Earth - Chapter 25 History...

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