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Origin of Life Origin of the Solar System • Earth is estimated to be ~4.6byo – Radiometric dating of rocks & meteors • Nebula: cloud of gas & dust in space • Nebula Hypothesis: – Gravity pulled much material together (Sun formed) – Planets: remaining materials Ancient Earth • Atmosphere contents: – Ammonia, H2O vapor, Methane, H2, • Climate: – Extreme heat due to meteor impacts & volcanic activity • Eventually Cooling: Water vapor condensed (oceans formed) Click on picture to play video clip Where did organic molecules come from? • Hypothesis: Energy from lightning created organic materials from inorganic ingredients • Experimental Set-Up: – Ammonia, H2O vapor, Methane, CO gases added – Electricity added (simulate lightning) • Result: Amino Acids & later nucleotides Murchison Meteorite Cell Formation? • Lipid membrane hypothesis • Liposomes – Spheres of lipids – Can form around organic molecules – Hypothesis: 1st cell membranes? RNA as Early Genetic Material • A hypothesis proposes that RNA was the first genetic material. – Ribozymes are RNA molecules that catalyze their own replication. – DNA needs enzymes to replicate itself. What about eukaryotic cells? How did they form? Eukaryotic cells may have evolved through endosymbiosis. • Endosymbiosis is a relationship in which one organism lives within the body of another. • Mitochondria and chloroplasts may have developed through endosymbiosis.