Variation refers to the differences in characteristics between individuals within a single species. There are two types of variation that we can observe:
Continuous variation refers to a characteristic that can have many different values and take on any value within that range. An example of this is human height. There is no fixed point at which someone becomes short or tall. Instead, height can range from very short to very tall and everything in between. It is continuous because a person’s height can fall within a wide range of values (e.g. 1.7m, 1.71m, 1.72m, 1.725…).
Continuous variation is also known as quantitative variation.
Some other examples of continuous variation are:
You can record data with a continuous range of values and plot it as a histogram. If you draw a line of best fit, the graph will look similar to the graph below. The graph shows a smooth bell-shaped curve of normal distribution.
The more data you collect and the more categories you use, the closer your results will be to the bell curve and a normal distribution
With continuous variation, the characteristics:
Discontinuous variation refers to the variation in a characteristic within a population that has a limited number of possible values, or categories. Individuals can only belong to one category. These characteristics are usually controlled by alleles of one gene or a small number of genes, and are not strongly influenced by the environment.
An example of discontinuous variation is blood type in humans. There are four categories (A, B, AB or O), and humans can only belong to one of these categories.
Some other examples of discontinuous variation:
When plotting discontinuous variation on a graph, the data is called discrete or categorical data. For example, with human blood types:
Features of discontinuous variation graphs: