5.5 Variation & Evolution

Types of Variation:

• Most characteristics are controlled by a number of different genes.
• The differences in the characteristics are not always clear.
• Continuous variation means that one characteristic within a population shows a gradient, for example, height. If an individual has inherited a number of alleles for height, they have the potential to grow tall. However, if they do not develop to their true potential it may be due to a poor diet. The differences have to be measured, and then the phenotypes can be told apart.
• Characteristics that are easy to tell apart are controlled by a single gene. This is called discontinuous variation. These genes may have two or more alleles, and will result in a time that can only be one or another, for example, black or white.

Origins of Variation:

• Non-heritable variation. Environmental factors can also determine phenotypic variation. For example, an organism will inherit genes for reaching a theoretical size. However, whether it reaches that size is determined…