Populations of animals exist in cooperative and competitive relationships with each other. For any species to thrive it must find access to food resources and be able to successfully reproduce. Ecologists have identified many methods for survival among the species of animals and have, consequently, described many of the survival techniques. Three fascinating relationships exist that intrigue both the scientist and the layperson. They are mutualism, parasitism, and commensalism.

Mutualism

Mutualistic relationships may be the most fascinating because of the cooperation that exists between species. Competitive relationships in which two or more species compete for the same resource are quite common. However, when two species evolve a pattern of survival from which both benefit, it is an interesting scenario for biologists to consider.

In a mutualistic relationship two organisms from entirely different species behave in a way in which both benefit. Most often, the two organisms...