Origins of Life to Cambrian Explosion

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Origins of Life to Cambrian Explosion
2010-06-20 19:25:54
evolution cambrian

Questions covering material from Lecture 09: Origins of Life from second year evolution course at UWO.
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  1. What are ribozymes?
    RNA capable of enzymatic function.
  2. What predictions arise from the RNA World Hypothesis?
    • Predicts that RNA is very ancient (more than DNA)
    • Predicts that RNA populations can evolve
    • Predicts that RNA can self-replicate (or replicate other RNA molecules)
  3. What evidence from ribosomes is there that supports the idea that RNA is very ancient?
    Ribosomes are found in ALL life and are highly conserved. They are also composed of protein but the protein is built around a framework of RNA.
  4. What was likely the first storage molecule, and why?
    RNA. Only RNA has enzymatic and data storage capabilities (though they are limited). Life could start out in an RNA world, and then evolve to use DNA as the more capable data storage system in order to make more complex proteins.
  5. What other evidence besides ribosomes is there that supports the idea that RNA is very ancient?
    Ribonucleoside triphosphates support the idea because they are essential components in the ATP, GTP formation in all organisms.
  6. What is an extant species?
    A species that is not extinct.
  7. What is the most recent common ancestor of all extant taxa known as?
    LUCA (last universal common ancestor)
  8. What is the Oparin-Haldane model?
    The idea that if you put together the right ingredients (water, methan, ammonium, hydrogen, etc), that these things would have a natural tendency to get together and randomly form organic molecules and perhaps even self replicating forms. It was tested out by Miller but the conditions they assumed of early Earth may not have been accurate.
  9. What are the alternatives to the Oparin-Haldane model?
    • Meteorite Model (organic molecules originate outside of Earth orbit, and assemble into living things once they arrive)
    • Panspermia (life originated somewhere outside of Earth, but would have to survive LONG term deep space travel)
  10. When did the first living things appear?
    Oldest fossil of cells 3.2-3.4 bya, and oldest chemical evidence of life (C12:C13) ratio 3.7 bya.
  11. What is endosymbiosis?
    An extreme form of lateral-gene-transfer involving the capturing of one organism by another, with the result being that both organisms form a mutualistic relationship. Think mitochondria and chloroplasts, with double membranes and their own DNA.
  12. What is the Universal Gene Pool Hypothesis?
    The theory that gene transfer occurred between species rather than between generations. Seems to be something that happens only with unicellular organisms. May have played an important role in early life on Earth (perhaps the ancestor of life is a pool of organisms that transferred DNA rather than just one species).
  13. What is the Ring of Life hypothesis?
    The idea that Eukaryotes are the result of a fusion of archaea and bacteria. Evidenced by the fact that Eukaryotes have some core cellular functions that resemble both groups, not either separately.
  14. What are some problems with the Ring of Life Hypothesis?
    Many proteins and genes are only found in Eukarya. Also, Archaea and Bacteria don’t have cytoskeletons, making fusion between them difficult.
  15. What are the three great eons?
    • Hadeon (earth formation until first life)
    • Archaean (first life until Cambrian explosion)
    • Phanerozoic (Cambrian explosion until now)
  16. What are the three great eras of our current eon?
    • Paleozoic
    • Mesozoic
    • Cenozoic

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