The History of Life on Earth

The History of Life on Earth - The History of Life on Earth...

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The History of Life on Earth (Brought to you by Science) Early Earth Conditions - 4.6 Billion Years Ago: sun and planets formed - 4.6-3.9 BYA: Meteoritic bombardment and heavy volcanic activity. - 3.9 BYA onwards: Reducing atmosphere (high in hydrogen content, no free oxygen; thick with H2O vapor, CO2, CO, CH4, NH3, H, etc.). How Did Life Start? - Problem: Organic molecules formed only by organic life - Can abiotic synthesis lead to organic molecules? - Darwin was one of the Frst to address this problem. 1871 The ±irst Organic Molecules - Reducing atmosphere - Oparin-Haldane Hypothesis: reducing atmosphere facilitates organic molecule formation - Test: Miller and Urey constructed early earth atmosphere. - Results: ±ormation of organic compounds. Synthesis of amino acids. - Caveat: Evidence suggests atmosphere (on average) was not a reducing environment. Evidence suggests that you need a reducing environment. - Deep Sea vents - Places on the earth where we still have reducing environment. - Volcanic activity produces a reducing environment - Thus, early life likely started near hydrothermal vents! - Note: Life around vents relies on sulfur for energy, NOT the sun. - Could be where the Frst cells evolved.
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- Extra-terrestrial - Light spectra indicate that 10-15% of galactic gas/dust contain organic molecules. - Example: in Muchison, Australia (1969) carbonaceouschondrite meteorite contains common amino acids. From Organics to Cells
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This note was uploaded on 09/21/2011 for the course BSC 2010 taught by Professor Bowes during the Spring '08 term at University of Florida.

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The History of Life on Earth - The History of Life on Earth...

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