Competition is the interaction between two organisms when both are trying to gain access to the same limited resource. When both organisms are members of the same species, such interaction is said to be "intraspecific competition." When the organisms are from different species, the interaction is "interspecific competition."

Intraspecific competition arises because two members of the same species have nearly identical needs for food, water, sunlight, nesting space, and other aspects of the environment. As long as these resources are available in abundance, every member of the community can survive without competition. When those resources are in limited supply, however, competition is inevitable. For example, a single nesting pair of bald eagles requires a minimum of 620 acres (250 ha) that they can claim as their own territory. If two pairs of eagles try to survive on 620 acres, competition will develop, and the stronger or more aggressive pair will drive...