Populations of animals are controlled by many factors. Natural selection is a broad term that describes one effect of these controls on population. For example, one form of population control that can result in natural selection is competition.

There are a number of essential resources upon which animals' lives depend. Whenever these resources are limited, animals are forced to compete for survival. Competition can be intraspecific, between the same species, or interspecific, between different species. Since resources are rarely abundant in any given environment, competition can be fierce. Three resources that animals are likely to complete for are space, water, and food.

Competing for Space

The availability of space is a primary consideration in any habitat. The actual territory in which an animal lives is vitally important since an animal's environment must be able to support the needs of each species. All animals must have enough room for...