Speciation

• Any population will contain natural genetic variation. This means it will contain a wide range of alleles controlling its characteristics that result from sexual reproduction and mutation.
• Natural selection


  In each population, the alleles that are selected will control characteristics that help the organism to survive and breed successfully.
• Part of a population becomes isolated because of new environmental conditions


  Alleles for characteristics that enable organisms to survive and breed successfully in the new conditions will be selected
• Alleles selected in new conditions

  Likely to be different from the alleles that gave success in the original environment
• Selection of different alleles


  Genetic variation between the populations will increase
• Speciation


  The characteristics change so much that they can no longer interbreed to produce fertile offspring with the original organisms
• How populations become isolated

  • Geographical isolation
  • Environmental isolation
• Geographical isolation


  • Two populations become physically isolated by a geographical feature, e.g. new mountain range, new river, area of land becoming an island
  • Earthquakes can separate areas of land
  • Volcanoes can produce completely new islands
  • Formation of islands often leads to speciation
• Environmental isolation


  • Climate changes in one area where an organism lives but not in other areas
  • Plants will flower at a different time of year
  • Breeding times of plants and animals linked with them will change
  • New species will emerge
• Speciation is taking place all the time all over the world