This is a gradual change in a characteristic across a population, it could be human height, mass and shoe size.

Continuous variation is represented as a histogram.

A histogram should show normal distribution, with most individuals around the average value and a few at the extremes.

Discontinuous variation

A characteristic of any species with only a limited number of possible values shows discontinuous variation. For example:

• gender (male or female)
• eye colour
• blood group

Human beings have one of four blood groups, A, B, AB or O.

There are no values in between (intermediate values), so this shows discontinuous variation.

Discontinuous variation is represented as a bar chart.