7.10 Speciation

• Speciation

  The creation of new species
• Biological species concept

  A group capable of interbreeding and exchanging genetic information to produce viable, fertile offspring
• Speciation

  Populations become reproductively isolated from each other
• Mechanisms that can separate members of the same population, potentially leading to speciation

  • Habitat isolation
  • Temporal isolation
  • Behavioral isolation
  • Mechanical isolation
  • Gamete isolation
• Pre-zygotic barriers


  Prevent production of a fertilized egg
• Pre-zygotic barriers

  • Habitat isolation
  • Temporal isolation
  • Behavioral isolation
  • Mechanical isolation
  • Gamete isolation
• Post-zygotic barriers

  Prevent a zygote from developing into a viable, fertile offspring
• Post-zygotic barriers

  • Hybrid inviability
  • Hybrid sterility
  • Hybrid breakdown
• Allopatric speciation

  Evolution of new species due to individuals from the same population being geographically isolated over a long period of time
• Sympatric speciation

  Evolution of a new species due to individuals being reproductively isolated from a surviving ancestral population, with no geographical barrier
• Punctuated equilibrium


  Evolution occurs rapidly after a long period of stasis
• Gradualism


  Evolution occurs slowly over hundreds, thousands or millions of years
• Divergent evolution


  The process of two or more related species becoming different through evolution
• Adaptive radiation

  Evolution of new species that allows empty ecological roles or niches to be filled
• Darwin's finches


  • Example of adaptive radiation, with changes in beak size and form enabling different species to utilize different food sources
• Isolation


  The first step in speciation, where a population of organisms becomes separated from the rest of its species.
• Variation


  The accumulation of genetic differences in an isolated population due to mutation, gene flow, genetic drift, and natural selection.
• Reproductive isolation


  The point at which the genetic differences between an isolated population and the original species become so significant that they can no longer interbreed.
• Species


  A group of organisms that can interbreed and produce fertile offspring.
• Temporal isolation :

  A pre-zygotic barrier, reproductive isolation between two populations where they reproduce at different times.
• Habitat Isolation

  
  

  Populations of a species relocate to a new habitat far far away from other populations of that same species
• Behavioral Isolation


  A pre-zygotic barrier, when species are reproductively isolated from other due to difference in behavior, basically the sex appeal of species
• Mechanical Isolation


  A pre-zygotic barrier, Sex organs of the species prevent interbreeding, (ex. snails with different shell orientations have their sex organs in different spots)
• Gamete Isolation


  A pre-zygotic barrier, the sperm and egg meet but no fertilization occurs
• Hybrid Inviability


  A post-zygotic barrier, short life span of the species, basically low hp
• Hybrid Sterility


  A post-zygotic barrier, when the offspring is infertile or unhealthy
• Hybrid Breakdown


  A post-zygotic barrier, the first generation is fertile but the next generation (F2) is infertile