Chapter 19 - Variation and natural selection

  • Created by: E456
  • Created on: 29-03-17 13:21


  • Differences between the features of different individuals are called phenotypic variation. 
  • Reasons for variations:
    • differences of individuals' genotypes (e.g. hair colour)
    • differences between the environments of individuals (e.g. a pine tree cannot grow in a small pot)
    • mutations.
  • In general, discontinuous variation is caused by genes alone.
  • Continuous variation is often influenced by both genes and the environment. 


  • An animal or plant that is well adapted to its environmnet is much more likely to survive than one that is not.
  • Xerophyte adaptations that help them to survive in their difficult environments:
    • closing stomata
    • waxy cuticle
    • hairy leaves
    • stomata on underside…


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