NATS 1940 Lecture Notes - Lecture 23: Harold Urey, Stanley Miller, Stromatolite
4 Jan 2018
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Document Summary
Rock-like structures formed by mucilage-secreting marine bacteria (prokaryotes) Oldest known stromatolites = 3. 5 billion years ago. Swirling dust cloud > denser regions condensed under gravity to form planets & the sun. Initially there was heavy bombardment by comets and asteroids. Comets are mostly ice > provided the earth with water. Earth had cooled, and liquid water had formed, by 4. 4 billion years ago. Life originated very soon after liquid water became available. Did contain water vapour, ammonia (nh3), methane (ch4), hydrogen (h2), carbon dioxide (co2) and carbon monoxide (c o) Stanley miller and harold urey, 1953: showed that lightning in the atmosphere could produce amino acids and sugars from these gasses. Earth"s early atmosphere was very different from today, did not contain oxygen. As the earth cooled > h2 escaped; water condensed to form oceans. We know that today on earth, living cells can only come from other living cells.
