Variation

Students should be able to describe simply how the genome and its interaction with the environment influence the development of the phenotype of an organism.

Differences in the characteristics of individuals in a population is called variation and may be due to differences in:

• the genes they have inherited (genetic causes)
• the conditions in which they have developed (environmental causes)
• a combination of genes and the environment.

Students should be able to:

• state that there is usually extensive genetic variation within a population of a species
• recall that all variants arise from mutations and that: most have no effect on the phenotype; some influence phenotype; very few determine phenotype.

Mutations occur continuously. Very rarely a mutation will lead to a new phenotype. If the new phenotype is suited to an environmental change it can lead to a relatively rapid change in the species.