Variation refers to the range of differences in traits/characteristics between individuals of the same species.
These traits can be solely affected by genotype, ie discontinuous variation or a combination of genotypes and environment, ie continuous variation.
7.1 Discontinuous variation
Discontinuous variation is shown when the species show distinct phenotypes for a specific trait. eg ABO blood type in humans. There are only four distinct blood types, A, B, O and AB. This type of variation is only controlled by genotypes which is controlled by few genes.
7.1 Continuous variation
Continuous variation is shown when the species show a large range of phenotypes for a specific trait. eg mass of the males.
This trait is determined by a large number of genes and it is also affected by the environment.