variation (biology)

In biology, a difference between individuals of the same species, found in any sexually reproducing population. Variations may be almost unnoticeable in some cases, obvious in others, and can concern many aspects of the organism. Typically, variations in size, behaviour, biochemistry, or colouring may be found. The cause of the variation is genetic (that is, inherited), environmental, or more usually a combination of the two. Some variation is the result of the environment modifying inherited characteristics. The origins of variation can be traced to the recombination of the genetic material during the formation of the gametes, and, more rarely, to mutation.

An example of inherited variation is blood groups in humans. An extreme example of variation produced by the environment is the loss of a part of the body from injury. An example of variation that involves the environment modifying inherited characteristics is height. The characteristic of being tall or short is inherited, but the availability of food in the environment determines the actual height of the individual.