Competition is a biological interaction among organisms of the same or different species associated with the need for a common resource that occurs in a limited supply relative to demand. In other words, competition occurs when the capability of the environment to supply resources is smaller than the potential biological requirement so that organisms interfere with each other. Plants, for example, often compete for access to a limited supply of nutrients, water, sunlight, and space.

Intraspecific competition occurs when individuals of the same species vie for access to essential resources, while interspecific competition occurs between different species. Stresses associated with competition are said to be symmetric if they involve organisms of similar size and/or abilities to utilize resources. Competition is asymmetric when there are substantial differences in these abilities, as occurs in the case of large trees interacting with plants of a forest understory.

Individuals of the...