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  • Variation
    • Interspecific variation
      • When there is a difference between species
    • Intraspecific variation
      • When there is a difference between the same species
    • Measurements
      • Usually measuring aspects of living organisms
        • All living organisms are different
          • Therefore many measurements are required
    • Variation is usually due to DNA
      • Differences between species are due to structure and sequence of genes in each organisms and how genes are expressed
      • A gene can only have an impact if it is switched on
    • Genotype is the genetic makeup which is inherited from parents
    • Pheotype is th collection of observable features that it has
      • Genotype + environment = phenotype
    • Cause of Variation
      • Sexual reproduction involves the production and fusion of gametes
        • Gametes are produced by meiosis
          • Variation occurs during meiosis
            • Cross over of parts of chromosomes
    • Joining gametes during fertilisation  introduces variation
      • Random mating occurs between individuals, 2 different sets of genes brought together
      • Random fertilisation, each event is random and which gamete pairs fuse is random
    • Mutation
      • Change in genetic material of an organism
        • Gene mutation is when the base sequence of a gene changes resulting 9 the change in the amino acid sequence
          • This may affect the overall shape and therefore functioning of the protein
      • Creates new alelle
    • Environmental
      • Expression of genes may be affected by the environment of an organism, characteristics are affected by environment
      • Some variation can be affected by both environmental and genetic factors


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