9.4 - Types of selection

• What’s directional selection ?

  Selection favours individuals that vary in once direction form the mean
• What’s stabilising selection ?


  Selection favours average individuals
• Example of stabilising selection ?

  Human birth weight , mean is the most advantageous
• Example of directional selection ?

  Antibiotic resistance in bacteria, mutation leads to more resistant bacteria
• What does directional selection result in, in terms of selecting phenotypes ?

  Phenotypes at one extreme of the pop. are selected for and those at the other extreme are selected against
• What kind of phenotypes does stabilising selection tend to eliminate ?


  The extreme phenotypes
• What does natural selection result in ?

  Species that are better adapted to their environment
• What are the 3 adaptations that natural selection can cause ?

  Anatomical, Physiological, Behavioural