Chapter 19 - Variation and natural selection

VARIATION

• 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. 

ADAPTIVE FEATURES

• 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…