BY2 - Evolution & Classification (2)

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  • Evolution & Classification
    • Evidence of Common Ancestry
      • Closely related species are recognised by their similar morphology.
        • E.G. Homologous Structures
          • Structures that have a common origin but serve a different function.
          • Pentadactyl Limb in vertebrates
            • Humans
              • Hand
              • Used for grasping and holding things
            • Cats
              • Legs
              • Used as support for jumping and walking etc.
            • Whales
              • Flipper
              • Used for movement in water - swimming
            • Bats
              • Wing
              • Used for flight
      • Biochemical Methods
        • Measure between the proportion of genes or proteins shared between different species to determine relatedness.
        • Proteins tend to be displayed as bands on an electro-phoresis gel.
        • Biochemical methods can reduce the mistakes made in classification due to convergent evolution.
          • The tendency of unrelated organisms to develop / acquire similar structures.
    • Analogous Structures
      • Structures that have the same function but a different origin.
      • E.G. The wings of a bird and an insect are not an indication that they are related.
    • Convergent Evolution
      • The process by which two lines of evolutionary development brings about superficially similar creatures.
      • When different groups of organisms are subjected to the same environmental selection pressures they tend to evolve similar design features.
    • Biodiversity
      • A measure of the number of species on the planet.
      • Rainforests and coral reefs are the most diverse habitats on the planet.
    • Species
      • A group of organisms that can interbreed and produce fertile offspring.
    • Extinction
      • The loss of a species.
      • Evolutionary history shows that biodiversity has gone through several 'bottlenecks' called mass extinctions.
        • Followed by the radiations of new species.
      • Causes
        • Deforestation
        • Construction
        • Development of industry
    • Evolution
      • The process by which new species are formed from pre-existing ones over very long periods of time.
      • Natural selection drives the evolution of new species .
        • Due to selective advantages developing and being inherited by the offspring and then passed on to new generations.
      • Development of a new species from a common  introduced into the environment
        • Adaptive Radiation


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