Types of Variation (WJEC GCSE Biology): Revision Note

Types of Variation

Higher Tier Only

• Phenotypic variation can be divided into two types depending on how you are able to group the measurements:

  • Continuous Variation is when there are very many small degrees of difference for a particular characteristic between individuals and they are arranged in order and can usually be measured on a scale

    • Examples include height, mass, finger length etc. where there can be many ‘in-between’ groups

  • Discontinuous Variation is when there are distinct differences for a characteristic

    • For example, people are either blood group A, B, AB or O; are either male or female; can either roll their tongue or not - there are no ‘in-betweens’

• When graphs of these data are plotted, continuous variation gives smooth bell curves (a result of all the small degrees of difference), whereas discontinuous gives a ‘step-like’ shape due to the discrete groups

Continuous variation graph

Height is an example of continuous variation which gives rise to a smooth bell-shaped curve when plotted as a graph

Discontinuous variation graph

Blood group is an example of discontinuous variation which gives rise to a step-shaped graph