evolution leads to speciation

• genetic variation in a population:

  mutation, meiosis (independent segregation & crossing over)

  random fertilisation/ fusion of gametes
• selective advantages

  organisms have phenotypes that give selective advantages more likely to survive and produce more offspring - change in allele frequency (evolution)

  • predation,disease and competition results to selective pressure
• disruptive selection

  change in the environment, individuals have too extreme traits, causing allele frequency to change and more individuals consist of the extreme traits
• speciation

  creating new species

  • original population becomes reproductively isolated
  • 2 populations that cant breed together - classed as 2 different species
• allopatric speciation

  separated geographically

  • as the population separates into 2 populations of the same species
  • random mutation causing variation in different populations
  • accumulate different mutations and advantageous ones are passed onto offsprings - change in allele frequency over time
  • DNA base sequences are genetically different, unable to interbreed and produce fertile offspring
• sympatric speciation

  variation (mutation) in fertilisation or courtship behaviours - different breeding times

  • reproductive isolation not geographical (occurs in the same habitat)
  • selected alleles are passed on causing a change in allele frequency
  • different species are unable to interbreed 
• genetic drift

  change in allele frequency between generations

  • results to evolution

  smaller the population the bigger the impact

  • evolution occurs more rapidly