Natural Selection 1- Revision

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  • Natural Selection and Genetic Modification
    • Natural Selection and Evidence for Evolution
      • Natural Selection- "Survival of the Fittest"
      • Bacteria provide Evidence for Evolution
        • 1) Bacteria can create new alleles which can change the bacteria's characteristics
          • eg. a bacterium could be less affected by a specific antibiotic (a drug designed to kill bacteria or prevent them from reproducing)
        • 2) For the bacterium, the ability to resist this antibiotic is a big advantage. In a host who's been treated to get rid of the infection, a resistant bacteria is able to survive than a non- resistant bacterium
          • And so it lives longer and reproduces many more times
        • 3) Leads to the allele for antibiotic resistance being passed on to lots of different offspring- it's just natural selection
          • This is how it spreads and becomes more common in a population of bacteria over time
        • 4) Antibiotic resistance provides evidence for evolution because it makes the bacteria better adapted to an environment in which antibiotics are present
          • As a result, antibiotic resistance becomes more common in the population over time
      • Fossils Provide More Evidence for Evolution
        • Fossil- Trace of any animal or plant that lived a long time ago. The deeper the rock, the older the fossil
        • Provides evidence for evolution as it shows how species have changed and developed over billions of years
    • Fossil Evidence for Human Evolution
      • 'Ardi'-- Fossil Hominid, 4.4 Million Years Old
        • 1) Structure of her feet suggests she climbed trees-- She had an ape-like big toe to grasp branches
        • 2) Long arms + short legs (more like an ape than a human) and her brain size was about the same as a chimpanzee's
        • 3) Structure of her legs suggests she walked upright like a human.
          • The structure of her hand bones also suggests she didn't use her hands to help her walk (like apes do)
      • 'Lucy'-- Fossil; Hominid, 3.2 Million Years Old
        • 4) Structure of leg bones suggests she waled upright but more efficiently than Ardi
        • 1) Had arched feet, more adapted to walking than climbing and no ape- like toe
        • 2) Size of legs and arms was between what you would expect to find in apes and humans
        • 3) Brain was slightly larger than Ardi's but still similar in size to a chimp's brain
      • Leakey and His Team found Fossil Hominids 1.6 Million Years Ago
        • 2) Short arm + legs are much more human than ape and his brain size was much larger than Lucy's-- similar to human brain size
        • 1) One of their finds was Turkana Boy-- 1.6 million year old fossil
          • He had a mixture of human and ape features but was more human- like than Lucy
        • 3) Structure of legs + feet suggests he was even better adapted to walking upright than Lucy


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