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2012-01-20 02:04:51
Bio 113

Bio113 unit one, chapter 22 the origin and history of life
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  1. Timeline leading to beginning of LIFE
    • 13.7 BYA: Universe began with the Big Bang
    • 4.6 BYA: Our solar system began
    • 4.55 BYA: The earth formed
    • 4 BYA: Earth Cooled (enough for the outer layers to solidify and Oceans to form)
    • 4 - 3.5 BYA: Life emerged
  2. Earth formation
    • Earth formed 4.55 BYA
    • For the first 1/2 billion years after earth formation it was too hot to allow water to accumulate on its surface.
    • By 4 BYA the Earth had cooled down enough for the outer layers of the planet o solidify and for oceans to begin to form.
  3. Condition on early Earth?
    Little or no Oxygen in the atmosphere

    • Atmosphere full of H-rich Gases
    • SH2, NH3, and CH4 etc.

    Also carbon dioxide, carbon monoxide, & gaseous nitrogen

    Subject to Meteor bombardments because early solar system full of debris

    Lots of Volcanic activity & intense Electrical storms

    No Ozone = lots of UV radiation exposure
  4. Name the four overlapping stages for the beginning of life. (in order)
    • 1. Origin of organic molecules were produced prior to the existence of cells
    • 2. Organic polymers may have formed on the surface of clay
    • 3. Cell-like structures may have originated when polymers were enclosed by a boundary.
    • 4. Cellular characteristics may have evolved via chemical selecion, beginnning with an RNA world
  5. Define "Chemical Selction"
    occurs when a chemical within a mixture has special properties or advantages that cause it to increase in number compared to other chemicals in the mixture
  6. Define "Fossils"
    preserved remains of past life on earth
  7. Facts about "Fossils"
    Many rocks with fossils are sedimentary

    Sediments pile up and become rock

    Organisms buried quickly, hard parts replaced by minerals

    Older rock is deeper, older organisms are deeper in rock bed
  8. Radioisotope Dating
    Fossils dated using elemental isotopes in rock

    Half-life – length of time required for exactly one-half of original isotope to decay

    Measure amount of a given isotope as well as the amount of the decay product

    Usually nearby igeneous rock dated
  9. Why move from an RNA world to DNA/RNA/protein?
    • DNA is less likely to suffer mutations
    • Relieve RNA of the info storage role so that it can do other functions
    • Proteins have greater catalytic potential, are more efficiency, provide structure & transport