Campbell Chapter 16 Notes

Campbell Chapter 16 Notes - Chapter 16(314341 Life began on...

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Chapter 16 (314-341) Life began on a young Earth All molecules close 2gether and then big bang 20 million years ago Solar System originated from swirling cloud of dust Most of the dust condensed in the middle and made the sun while the others scattered around became stars Dust and ice particles were drawn together by gravity forming the planets Earth was created 4.6 billion years ago as a cold world Heat formed from meteor impacts, radioactive decay, and gravity compaction which eventually formed a molten mass This molten mass sorted into layers w. different densities o Nickel and Iron mostly became concentrated into the center and became the core o Less dense mantle surrounded core, and the really less dense mantle solidified into the crust 1 st atmosphere was filled w/ hot hydrogen gas (H2) Gravity was weak back then so this atmosphere escaped into space So a 2 nd atmosphere How did life originate? Louis Pasteur stated that all life today arose from the reproduction of preexisting life (Darwin?) o This ended the argument of Spontaenous Generation but doesn’t explain how life started Earliest life forms may have been molecules that only did self-replication and had metabolism o First organic molecules arose from inorganic materials, which then joined to form polymers Stanley Miller’s experiments showed that organic molecules could have arisen on a lifeless Earth Stanley Miller proves: Present-day conditions on Earth don’t allow for spontaneous synthesis of organic compounds because atmosphere is rich in O2 o Oxygen is corrosive which extracts electrons from chemical bonds o Before prokaryotes added O2 earth had an oxygen less, electron adding atmosphere which combines simple molecules Energy from U.V. Radiation (currently screened out by Ozone layer), lightning Miller predicted that organic molecules would form inorganic molecules under early Earth conditions o Primeval Sea= Flask of warm water o Atmosphere= Water Vapor, H2, CH4, NH3 o Lightning= Electrodes discharged sparks into gas mixture to mimic lightning After experiment organic compounds + amino acids that make up organisms found in solution This supports idea that many organic molecules that make up living organisms could have been formed before life arose on early Earth
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The First polymers may have formed on hot rocks or clay After small organic molecules formed, 2 nd major step was formation of organic polymers (proteins) o Polymers are synthesized by dehydration reactions which release a water molecule for each monomer added to the chain In living cells enzymes catalyze these reactions, In labs heat from hot sand/clay/rocks
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