• Speciation is when a new species forms from an existing species
    • This is due to reproductive isolation which can be allopatric or sympatric
  • Allopatric speciation occurs due to geographical isolation
    • Eg a population of the species gets trapped in an isolated area with a different climate
    • Over time, the population will adapt to the new climate leading to changes in allele frequency and therefore changes in phenotype
    • This results in individuals from the two populations being unable to breed to form fertile offspring, which means that they are different species.
  • Sympatric speciation is similar to allopatric speciation but doesn’t require geographical isolation
    • This can be due to:
      • polyploidy (different chromosome numbers)
      • seasonal isolation (different individuals have different flowering or mating seasons)
      • mechanical isolation ( prevent mating)
      • behavioral isolation (incorrect or different courtship rituals prevent mating)
  • Genetic drift is when a change in allele frequency occurs by chance
    • This can lead to evolution but often has a greater effect in smaller populations
  • The diversity of life on earth today results from millions of years of evolutionary change

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