genetic diversity & natural selection

• Genetic diversity


  The number of different alleles of genes in a population
• Natural selection


  • Leads to evolution in populations
  • Results in species becoming better adapted to their environment
• Evolution


  The change in allele frequency over many generations
• Types of adaptations


  • Anatomical: structural features (e.g. beak shape of a bird)
  • Physiological : chemical reactions within the body (e.g. snake producing venom)
  • Behavioural : how organisms behave (e.g. penguins huddling together for warmth)
• Directional selection


  • Occurs when there's a change in environment
  • modal trait changes
• Stabilising selection


  • Occurs when there's no change in environment
  • modal trait stays the same
  • over many generations more organisms have desired trait and most of extremes lost (decrease in allele range)
• Gene definition


  A gene is a sequence of DNA bases that codes for polypeptide