GCSE Biology (CIE)

Topic Summaries

Evolution and natural selection

Variation

  • Differences in the characteristics of individuals in a population are called variation.
  • The phenotype of an organism is determined by the genome and the genome’s interaction with the environment.
    • Some characteristics are determined purely from inherited genes (e.g. biological sex and blood group) and some purely by the environment (e.g. tattoos, scars).
    • Some characteristics are determined by genetics and the environment, where genetics predetermines the potential for a characteristic and the environment determines how much of this potential is reached (e.g. intelligence).
  • There is usually extensive genetic variation within a population of a species.
  • All genetic variation arises from mutations. Most mutations have no effect on the phenotype, and very few mutations determine phenotype. If the new phenotype is better suited to an environmental change, it can lead to a rapid change in the species.

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