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Origin of Life (overview )

Origin of Life (overview ). Chemical evolution Replicators - RNA or DNA? Individuality: Protocells --> cells Prokaryotes: Earliest true cells (~3.5 bya) Endomembrane system : Increase in cellular complexity

siobhan-crofton
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Origin of Life (overview )

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  1. Origin of Life (overview) • Chemical evolution • Replicators- RNA or DNA? • Individuality: Protocells --> cells • Prokaryotes: Earliest true cells (~3.5 bya) • Endomembrane system: Increase in cellular complexity • Endosymbiosis: Further increase in eukaryote complexity and expansion of biochemistry • Multicellularity: Cooperative grouping of differentiated, clonally related cells

  2. Logic of Origin of Life • Diverse environment • Lots of Time--> perhaps hundreds of millions of years • Non-oxidizing atmosphere--> without lots of O2 around, organic molecules are much more stable • Organic molecule stability without O2 allowed life to evolve slowly from nonliving material • Organic Molecules

  3. Logic of Origin of Life • Energy- volcanoes, deep-sea vents, lightning, sun light, chemicals from space • natural selection: • Stuff that is durable and easily made tends to accumulate • Chemicals that are stable, and can duplicate themselves, naturally increase in abundance 3. Little Early Competition

  4. Oparin’s hypothesis Early Earth needed • Water vapor • Carbon dioxide • Methane • Nitrogen • ammonia

  5. Miller & Urey Experiment (1953) Miller and Urey devised the experiment

  6. Extraterrestrial Energy Sources

  7. oceanic geothermal vents (underwater geysers and hot springs) Terrestrial Energy Sources

  8. Laboratory Protobionts Shown is some degree of abiotic individuality

  9. Relative Vs Absolute Dating • Relative dating: • Geological time scales • Relative position in rock strata • Index fossils- trilobites • Absolute dating: • Actual “clock” • E.g., radioactive decay

  10. Radiocarbon Dating

  11. The Carbon 14 Dating Process • 1 atom of C14 for every 1013 C12 atoms in the atmosphere • Once an organism dies, the C14 is trapped and decays. Half-life is about 5800 years

  12. Geologic Record • Bacteria and Archea diverge- 2-3 bya • Photosynthetic bacteria produce oxygen- 2.5 bya • Eukaryotes emerge- 2 bya • Plants emerged from green algae ~700 mya • Fungi and animals emerge from uni-cells ~ 700 mya • First terrestrials- 450 mya

  13. Mass Extinction • Permian (250 million years ago): 90% of marine animals; Pangea merge • Cretaceous (65 million years ago): death of dinosaurs, 50% of marine species; low angle comet or meteor ( ~10 km across)

  14. Snowball Earth (latest ~650 mya) • Severe ice ages covered the entire planet • Multicellular organisms survived deep in oceanic thermal vents and clustered together for protection • Meteor impact could cause another

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