AST251 FEBRUARY 27.docx

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University of Toronto St. George
Astronomy & Astrophysics
Susan Pfieffer

AST251 FEBRUARY 27 2012 UTORONTOPEERSCHOLARCA LOGIN WITH UTORID AND PASSWORD ast251springThe origins of life most likely occurred45 and 35 isotope ratios 4 billion and fossils 35 gyrThe Cambrian explosion refers to545 million years ago 1 Origins 2 Oxygen and eukarya 3 Cambrian explosion 4 Kt event5 HumansHow did it startEssential elements already on earth and water brough to usSteps needed to build larger molecules Separate interior from exterior of cellsReplication with heredity and rna and dna The early atmosphereLittle oxygen was dominated by H compounds red or orange and hot bc earth was still hot Sun stable Earth almost completely of water2 crust ocean which is heavy sinlks and lighter continental crustWater of earth only makes up 1 percent of the mass4 km average depth2 percent water all land convered by water The millerurey experiment1920s gaqs mixture of earths atmosphere and added sparks to it produced different types of amino acids important step in demonstrating complex molecules can form spontaneously Early ideasPungent ponds organic soup vuln to uv and impactsAtmosphere different from what they assumed to dilute in the ocean one way vs the other disequilibrium one phase more energetically favor in soup no direction mid ocean ridges
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