Despite their close relationship, wolves and dogs show a number of physical and behavioural differences.

Biology of gender is the scientific analysis of the physical basis for behavioural differences between men and women.

A further spreading of hybrids might hasten the process of interbreeding by reducing behavioural differences.

However, the two species are easily distinguished through examination of life history, ovipositor and behavioural differences.

The species has been isolated by a variety of mechanisms including behavioural differences and genic incompatibility but hybridization is not unknown.

Sexual selection is a widespread natural process, and the cause of most behavioural sexual differences.

Nordgreen said that the behavioural differences they found showed that fish feel both reflexive and cognitive pain.

Male colour polymorphism may be indicative of behavioural differences.

During the breeding season in May and June these behavioural differences between the sexes.

Although superficially similar, there are a number of physical and behavioural differences between the American and European bison.