Fossils, Extiction and Speciation

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  • Fossils, Extinction and Speciation
    • Animals and Plants
      • Fossils are the remains of organisms and provide the evidence that organisms lived ages ago
      • Fossils form in rocks from 3 ways:
        • 1) Gradual Replacement by minerals- teeth, shells, bones
        • 2) Casts and Impressions- sometimes buried in a soft material, hardens round it and organism decays leaving a cast of itself
        • 3) Preservation- in amber and tar pits where ther's no oxygen, moisture, so decay microbes can't survive
    • How did life begin?
      • Various hypotheses, but no-one
      • Hypotheses can't be supported or disapproved- lack of valid and reliable evidence
      • Fossils that formed millions of years ago have been destroyed by ecological activity
    • Extinction
      • Environmental Changes
      • New predators
      • New diseases
      • Can't compete
      • Catastrophic event
      • New species develops
    • Speciation
      • The develop of a new speicies
      • Occurs when populations of the same species becomes so different that they can no longer breed together
    • Isolation
      • Speciation
        • The develop of a new speicies
        • Occurs when populations of the same species becomes so different that they can no longer breed together
      • Where populations of a species are separated
        • Due to a physical barrier that geographically isolate some individuals from the main population
          • Conditions on either side of the barrier will be slightly different, different characteristics will become more common- natural selection
    • Natural Selection
      • Each population shows variation- wide range of alleles
      • Conditions on either side of the barrier will be slightly different, different characteristics will become more common- natural selection
      • In each population, indibviduals with charcteristics make them better adapted- better chance of survival- breed successfully
      • Alleles that control beneficial characteristics, more likely to be passed on

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