Speciation

• Speciation


  The evolution of new species
• Types of reproductive isolation

  • Behavioral isolation
  • Geographic isolation
  • Temporal isolation
  • Mechanical isolation
  • Genetic isolation
• Allopatric speciation


  Speciation that occurs when a population becomes geographically isolated from the main population
• Sympatric speciation


  Speciation that occurs without geographic isolation
• Process of speciation


  1. Reproductive isolation

  2. Genetic divergence

  3. Reduced gene flow

  4. Formation of new species
• Adaptive radiation


  When a single species has evolved, through natural selection and other processes, into several different species in different ways
• Species


  A population of interbreeding organisms capable of producing fertile offspring
• Example of different species

  • Donkey and horse
  • Produce a mule, which is infertile
• Reproductive isolation


  When something prevents members of two populations from interbreeding and producing fertile offspring
• Speciation occurs when reproductive isolation occurs
• The gene pool of a population becomes separated from one another when reproductive isolation develops</b>
• Geographic Isolation


  Populations are separated by geographic features such as rivers, mountains, volcanic eruptions, deforestation, bodies of water or something man-made
• Temporal Isolation


  Populations have courtship and mating at different times of the day, week, season or year
• Anatomical/Mechanical Isolation


  Two populations are not capable of interbreeding because their reproductive organs don't fit together
• Genetic Isolation


  There are Chromosomal differences between populations due to mutations or errors in cell division
• Reproductive isolation does not always require a physical barrier
• Allopatric


  Geographically separate populations
• Sympatric


  Not geographically separate, isolation could be due to temporal, behavioral, anatomical or mechanical challenges
• Stages of Speciation in Darwin's Finches

  1. Founders arrive

  2. There is reproductive isolation

  3. Interbreeding stops and there are two separate gene pools

  4. Populations become adapted to local environments

  5. Enough genetic changes occur over time that there are now 2 species

  6. Even if they were to mix again, they can no longer interbreed to produce fertile offspring
• There are currently 13 different species of finch in the Galapagos Islands
• Genetic drift has a larger impact on smaller populations