Topic Summaries

Variation

IGCSE > Biology > Pearson IGCSE > IGCSE Biology Topic Summaries > Evolution and natural selection > Variation
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Stem cells, microscopy, and microorganisms

Pathogens and non-specific immunity

Plant disease and monoclonal antibodies

Resource cycles and environmental change

Science skills: Measuring results

  • 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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