Speciation

• What is speciation?

  Evolution of new species from existing ones
• What is a species?

  group of individuals that have a common ancestry that share the same genes (but different alleles) and are capable of interbreeding to produce fertile offspring
• members of a species are reproductively separated from other species
• Allopatric speciation 


  -due to geographical isolation e.g barriers such as oceans and deserts

  -this prevents them interbreeding

  -if environmental conditions on both sides vary, different selection pressures occur

  -change in allele frequency occur

  -gene pools are separated and become reproductively isolated (unable to produce fertile offspring)
• Sympatric speciation


  -occurs due to random mutations of species that live in the same area

  -become reproductively separated

  -differences in gene pools

  -unable to interbreed and produce fertile offspring (reproductively seperated)
• behavioural changes


  -group of individuals develop changes in their courtship behaviours

  -no longer attracted to individuals of the opposite sex for mating
• mechanical changes


  -changes in genitalia that prevents successful mating
• seasonal changes


  -individuals from the same population develop different flowering/mating seasons

  -can become sexually active at different times compared to the rest of the population
• Genetic drift


  -chance affects which individuals in the population survive, breed and pass on their alleles not selectional pressures or environmental factors

  -causes a change in the allele frequencies in the gene pool of a population