5.2 Natural Selection

5.2 Natural Selection

1. Nature of Science

   • The theory of evolution by natural selection
     • TOK
       • How much evidence is required to support a theory?
       • What sort of counter evidence is required to refute it?
     • Adaptations are characteristics that make an individual suited to its environment and way of life
       • Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring
         • Species tend to produce more offspring than the environment can support
           • 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
     • Characteristics acquired during the lifetime of an individual are not heritable
     • Examples
       • Antibiotic resistance
       • Beaks in the finches on Daphne Major

2. Variation

   • Natural selection can only occur if there is variation among members of the same species
     • Sexual reproduction
     • Mutations
     • Meiosis