Old and New Species

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  • Old and New Species
    • Origins of life on Earth
      • the earth is about 4500 million years old and life began about 3500 million years ago
      • fossils may be formed in various ways:
        • from hard parts of animals that don't decay easily (bones, teeth, shells, claws etc)
        • from parts of organisms that have not decayed because some of the conditions for decay are absent
        • when parts of the organism are replaced by other materials, such as minerals, as they decay
        • as preserved traces of organisms (footprints, burrows etc)
      • most organisms that died did not leave a fossil because the conditions for fossil formation were absent
        • many early life forms had soft bodies so few traces were left
        • some traces that were left behind could of been destroyed by geological activity (earthquakes)
    • Fossil evidence
      • extinction means that a species which once existed has completely died out, it can be caused by:
        • a new disease killing all members of a species
        • the environment changing
          • a geological event may occur and destroy a habitat (volcanic eruption)
          • climate change
          • following a collision of giant asteroid and Earth
        • a new predator may evolve and kill/eat all of a species
        • a new competitor may evolve, the original species may be left with little to eat
        • natural changes in species occur over time
    • Isolation and Evolution of New Species
      • New species can arise from existing species if a group becomes isolated from the rest
      • Geographical isolation could occur if an island separates from the mainland etc
        • organisms left on the island may be exposed to different environmental conditions, food availability or predators
        • Natrual selection will occur in both areas


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