Understandings

• 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. [Students should be clear that characteristics acquired during the lifetime of an individual are not heritable. The term Lamarckism is not required.]
• 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.