18.5 - Isolation + speciation

• Define speciation

  The evolution of new species from existing ones
• Why are members of different species referred to as reproductively separated ?

  They can’t reproduce to produce fertile offspring
• Describe how speciation occurs

  • a population becomes separated from others and undergoes different mutations
  • also experience different selection pressures due to different environments
  • natural selection leads to changes in allelic frequencies of each population
  • adapt to their environment due to different allele combinations, adaptive radiation
  • can no longer interbreed to produce fertile offspring, different species with different gene pools
• What are the 2 types of speciation ?

  Allopatric and sympatric
• What does allopatric speciation mean ?

  Occurs when two populations become geographically separated
• How does allopatric speciation work ?

  • Populations get separated geographically
  • Different environments and selection pressures
  • Natural selection occurs, populations adapt to their environment
  • Adaptation leads to evolution of a ew species
  • Speciation occurred, can no longer interbreed to produce fertile offspring
• What’s sympatric speciation ?

  When reproductive isolation occurs within a population in the same area
• When can sympatric speciation occur ?

  Different breeding seasons