Competitive exclusion is the interaction between two or more species that compete for a resource that is in limited supply. It is n ecological principle involving competitors with similar requirements for habitat or resources; they utilize a similar niche. The result of the competition is that one or more of the species is ultimately eliminated by the species that is most efficient at utilizing the limiting resource, a driving force of evolution. The competitive exclusion principle or "Gause's principle" states that where resources are limiting, two or more species that have the same requirements for the limiting resources cannot co-exist. The coexisting species must therefore adopt strategies that allow resources to be partitioned so that the competing species utilize the resources differently in different parts of the habitat, at different times, or in different parts of the life cycle.