Old and New Species - B2 Unit 6

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  • Old and New Species - B2 Unit 6
    • The Origins of Life
      • Scientists cannot be exact about when life started on Earth
        • There is little repeatable or reproducible evidence
      • Fossil are remains of organisms from many years ago which are found in rocks
        • We can learn how different organisms changed
        • Different ways of formation
          • Hard parts that don't decay easily - bone, teeth, shell
          • Conditions needed for decay not present - lack of oxygen
            • Buried deep underground or in ice
          • Parts of animal mineralise - turn into rock
          • Preserved traces - footprints, feaces, burrows
      • Early life forms mainly sot bodied so left no fossil
      • Approx
        • Earth began 4500 million years ago
        • Life began 3500 million years ago
    • Exploring the Fossil Evidence
      • Fossil record can show how much organisms have changed over time
        • some have evolved then become extinct
      • Extinction
        • A species that once existed has completely died out
        • Causes
          • A new disease kills
          • Environment changes
          • New predator may evolve
          • A new competitor may evolve using all the resources
          • A single catastrophic event
            • Volcanic eruption
            • Metorite
          • Sudden climate change
        • Occurs only when there is a change
    • Isolation and Evolution of New Species
      • New species can evolve from existing
        • Natural cycles linked to environmental change
      • New species arise when two populations become isolated
        • Organisms of the same species are separated by something they cannot cross
          • Geographical isolation
        • Organisms  adapt to the environment they're in
      • Speciation - caused by isolation + geographical change
        • Each population has own set of alleles control characteristics needed for environment
          • natural selection
        • Each environment has different predators, food supply and environment
          • evolve differently
        • speciation has occurred when the two populations that were once the same species can no longer successfully interbreed


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