Ecology deals with the interactions between species and the necessary conditions of existence in the environment to which they are adapted. At the level of individual animals, plants and microbes these adaptations comprise webs of perception and action evolved to ensure resources are available to maintain growth and reproduction.

Behavioural interactions are at the heart of ecology where they function to unite individuals into more or less stable social structures. In particular, the structures determine and regulate the relations of individuals to one another. They provide such external adaptation to the physical environment, and such internal adaptation between the component individuals or groups to make possible an ordered social life. Each species has evolved a behaviour structure that is an harmonious whole to maintain the sum of its parts in a steady state biochemical equilibrium with its environment. It survives and flourishes because it successfully maintains external social solidarity among its members, and chemical integrity amongst its internal organs and cells.