Fossils, Extinction and Speciation

Fossils
1. Remains of plants and aniamals
2. From million of years ago
3. Found in rocks
4. How they're formed
  1. Gradual replacement by minerals
    1. Teeth, shell, bone decay slowly
      1. Replaced by minerals as they decay
        Rock-like substance formed
        Shaped like original part
        Surrounding sediments turn to rock
        Fossils remain distinct
  2. Casts and Impressions
    1. Organism buried in soft material
      1. Clay hardens around organism
        Organism decays
        Cast created
        Include burrows and roots
        Footprints can also leave impressions
  3. Preservation
    1. In amber and tar pits
      1. No O2 or H20
        Decay microbes can't survive
        Glaciers are too cold
        Peat bogs are too acidic
Speciation
1. Development of a new species
  1. When populations become too different
    1. Can't breed to produce fetile offspring
2. Isolation
  1. Physically divides a population
    1. eg. floods, earthquakes
      1. Conditions either side of divide different
        Natural selection occurs
        Different characteristics for each population
        Eventually two populations change too much
        So can't produce fertile offspring
        Become two separate species
        Population shows variation - Wide range of alleles
        Individuals in each population have better characteristics to survive
        Better adapted individuals more likely to successfully breed
        Alleles controlling beneficial characteristics passed on to offspring
        Eventually beneficially characteristic are passed on to an entire new generation
Extinction
1. Organisms can't evolve quickly enough
  1. Sudden environmental change
  2. New predator
    1. Humans
  3. New disease
  4. Can't compete with new species
2. Natural Diaster
  1. Volcanic eruption
  2. Collision with asteroid
3. New species develops
  1. Speciation

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Fossils, Extinction and Speciation

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