BY5.5 Isolation and Speciation

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Isolation and Speciation

  • breeding subunits become isolated from one another and evolve along separate lines
  • if reunited the sub units would be incapable of breeding successfully as they are separate species
  • factors leading to the formation of new species:
    • geographical isoaltion
    • habitat changes
    • changes in body form
    • changes in breeding mechanisms


  • within a population breeding subunits are called demes
  • individuals within a deme are more likely to breed with one another more often than with individuals of another deme
  • new species arise when barriers to reproduction occur
  • the gene pool is divided
  • the flow of genes between separate demes stops
  • this is known as an isolating mechanism
  • long term speciation will lead to 2 new species that are incapable of interbreeding
  • seperate species will have their own gene pool

Isolation leading to speciation:

  • for a new species to develop from a population an isolating mechanism is needed
  • 2 main forms of isolating mechanisms
    • geographical…


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