7.3.7 Types of Speciation

• Speciation - the creation of new species due to reproductive isolation
• Allopatric Speciation - the creation of new species due to geographical isolation
• Steps of Allopatric Speciation:

  1. Original population geographically separated leading to reproductive isolation because geographical barrier prevents reproduction
  2. Both populations accumulate different beneficial mutations (this will vary in populations)
  3. DNA differences overtime will cause the species to be too genetically different
  4. This leads to both species being unable to interbreed to reproduce a fertile offspring
  5. Therefore they become classified as two different species
• Sympatric Speciation = when a population splits into two separate species, but they are still in the same geographical area
• Ecological separation: Populations are separated because they live in different environments within the same area
• Ecological separation: Populations are separated because they live in different environments within the same area
• Evolution can also occur via genetic drift

  • This is when chance (instead of environmental selection pressures) affects which individuals in a population survive, breed and pass on their alleles
  • Over time, some alleles can be lost or favoured purely by chance
• Genetic drift = When there is a gradual change in allele frequencies in a small population due to chance and not natural selection
• In large populations, genetic drift is less likely to have an effect because any chance variations in allele frequencies usually even out across the whole population
• Founder Effect = A genetic bottleneck that occurs when only a few members of one population migrate or move away from another population.
• Bottleneck = a small population of a species that is isolated from the rest of the population