phenotype variation shown in quantitative traits which are distributed from one extreme to another in an overlapping, continuous spectrum; examples of traits that show continuous variation are height, weight, and intelligence.

variation with respect to a certain trait, among phenotypes that cannot be classified into clearly distinct classes, but rather that differ little, one from another controlled by quantitative genes.

Variation showing an unbroken range of phenotypic values.

A gradation of small differences in a particular trait, such as height, within a population; occurs in traits that are controlled by a number of genes.

Occurs when the phenotypes of traits controlled by a single gene cannot be sorted into two distinct phenotypic classes, but rather fall into a series of overlapping classes.