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LifeonEarth - How did life begin? 13 - 17 bya: 4.6 bya:...

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How did life begin? 13 - 17 bya:Big Bang formed the universe 4.6 bya:Our solar system formed 4.55 bya:Earth formed 4 - 3.5 bya:Life emerged • Life requires interplay between DNA, RNA and proteins • Living cells come from pre-existing cells 4 Overlapping Stages: 1)Nucleotides and amino acids produced prior to existence of cells 2)Nucleotides and a.a.’s became polymerized to form DNA, RNA and proteins 3)Polymers became enclosed in membranes 4)Polymers enclosed in membranes evolved cellular properties
Primitive Earth Reducing Atmosphere Hypothesis Primitive atmosphere: - H2O vapor, N2, CO 2 - Small amounts of H2 and CO Little free oxygen (reducing atmosphere) Originally too hot for liquid water As earth cooled, water vapor condensed to liquid water Primordial soup Monomers evolved and joined to form Polymers1920’s: Oparin and Haldane Abiotic Synthesis
First Biomolecules Miller’s & Urey’s Apparatus & Experiment. Miller and Urey (1953) Showed that biochemicals could be produced from simple nonbiological sources - Primitive atmospheric gases - Strong energy sources More recent: Neutral environment - CO, CO2,N2, H2 O Organics can be made under a variety of conditionsYielded HCN, CH2 O, glycine, sugars, a.a.’s, N-bases
Alternative Mechanisms Deep-sea vent Hypothesis - 1988 • Key organics arose at deep-sea vents • Superheated water (3000 F) rich in H2 S and Metal ions mixes with cold seawater •
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