Allele frequency - species and speciation

Breif revision notes on allele frequency, species and speciation

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  • Allele Frequency
    • Affected by mutation
      • harmful allele frequency decreases
      • change in base sequence and resulting in change in protein structure
      • neutral maintains frequency
      • beneficial allele frequency increases
        • higher chance of survival or reproduction so they pass genes down
        • causes selection pressure
    • Species and speciation
      • relies on isolation
        • stops gene flow
        • allopatric speciation is mainly geographical isolation
          • barriers
          • oceans
          • mountains
          • motorways
        • sympatric speciation
          • behavioural isolation
            • feeding times/courtship
          • temporal isolation
            • mating seasons
          • mechanical isolation
            • reproductive organs
          • habitat isolation
            • within same area occupying different levels
          • gametic isolation
            • gametes fail to "recognise" each other so don't reproduce
          • pre-zygotic mechanisms
            • allopatric speciation is mainly geographical isolation
              • barriers
              • oceans
              • mountains
              • motorways
            • prevent fertilisation
        • post-zygotic isolating mechanisms
          • low hybrid zygote vigour
            • fail to develop properly
          • low hybrid adult viability
            • offspring don't develop properly
          • hybrid infertility
            • offspring infertile
      • natural selection and evolution
      • species = animals which can successfully reproduce to produce fertile offspring
        • results in gene flow between organisms
    • relative frequency of an allele within population

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