Chapter_17_to_post

Chapter_17_to_post - History of Life on Earth How did life...

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History of Life on Earth
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How did life begin?
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A few centuries ago: 1. People thought that new living things appeared all of the time 2. 1609. “There is a tree… frequently observed in Scotland. From this tree leaves are falling; upon one side they strike the water and slowly turn into fishes, upon the other side they strike the land and turn into birds.”
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Spontaneous Generation Refuted (Fig. 17-1) -mid-1800s Louis Pasteur Broth in flask is boiled to kill preexisting microogranisms As broth cools, condensing water collects, sealing the mouth of the flask If neck is later broken off, outside air can carry microorganisms into broth
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Conditions on Early Earth Atmosphere: 1. CO 2 ; CH 4 ; NH 3 ; H 2 ; N 2 ; HCl; H 2 S; H 2 O -Similar to Jupiter today 1. No free oxygen 2. Frequent storms w/ lots of lightening 3. Frequent volcanic eruptions 4. Frequent meteor impacts 5. UV light from the sun 6. No ozone layer
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Earth Before Life Arose 1. Earth is about 4.6 billion years old 2. Life arose about 3.8 billion years ago a. Chemical traces in rocks 3.8 BY b. Fossil bacteria in rocks 3.5 BY c. No spontaneous generation now, but must have happened then
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= 40 K = 40 Ar Rate of Decay of 40 K to 40 Ar (Fig. E17-1) Proportion of original 40 K remaining in rock Billions of years since melting of rock Potassium 40 ( 40 K) naturally decays to argon 40 ( 40 Ar)
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Electric spark simulates lightning storm Organic molecules appear after only a few days Condens er Cool water flow Electric spark chamber CH 4 NH 3 H 2 Boiling chamber Gases of primeval atmosphere Purified water H 2 O H 2 O
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How to Assemble a Living Thing 1. Accumulation of organic molecules 2. Catalyze reactions 3. Reproduce from stored genetic info 4. Separate the living thing from the outside environment
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Now: DNA → RNA → Protein - Need proteins to synthesize more DNA The Chicken or the Egg?
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This note was uploaded on 04/07/2011 for the course BIOL 1001 taught by Professor Minor during the Spring '08 term at LSU.

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Chapter_17_to_post - History of Life on Earth How did life...

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