5.2  Natural Selection

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Essential Idea:

The diversity of life has evolved and

continues to evolve by natural selection


  • Natural selection can only occur if there is variation among members of the same species
  • Mutation, meiosis and sexual reproduction cause variation between individuals in a species
  • Adaptations are characteristics that make an individual suited to its environment and way of life
  • Species tend to produce more offspring than the environment can support
  • Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring
  • Individuals that reproduce pass on characteristics to their offspring
  • Natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species


  • Changes in beaks of finches on Daphne Major
  • Evolution of antibiotic resistance in bacteria