• Speciation: When a species splits into more species
  • Adaptive radiation: 1 species becomes many
  • Divergent evolution: 1 species becomes 2

Ways for separation to occur

Pre-zygotic

  • Habitat (ecological) isolation
  • temporal (time/seasonal)
  • behavioral
  • mechanical
  • gametic (broadcast spawners: external fertilization (usually aquatic))
    • Sex cells

Post-zygotic

  • reduced hybrid fertility
    • Horse and donkey together can only make mules, but mules cannot mate mules, only horse and donkey together
    • hybrid can live but cannot reproduce
  • reduced hybrid viability
    • Gets to a certain point in development, but most likely will die before reproductive age
    • hybrid can live but next generation will be very weak
    • breakdown in ability to sustain
  • hybrid breakdown

Basically organism is formed but cannot live because of one of these three things

Allopatric

  • pop is split into two and isolated (by a barrier)

Sympatric

  • together
  • plants
  • polyploid
  • (many)(chromosome set #)