Competition Among Animals
In the theory of survival of fittest, competition was a major reason for evolution and extinction. Here from several examples from natural or artificial breeding, effect and theory of competition has been explained.
When Darwin spoke of the struggle for existence and survival of the fittest in nature, he was convinced that competition is a potent force in evolution. It is believed that competition occurs among related species for the same limited resource. But totally unrelated species can also compete for the same resource. Example In some shallow South American lakes visiting Flamingos and resident fishes compete for zooplankton in the lake.
Competition is a process in which the fitness of one species is significantly lowered in presence of another species. The Abingdon tortoise in Galapagos Islands became extinct within a decade after goats were introduced on the island, apparently due to greater browsing efficiency of the goats. Another evidence for occurrence of competition comes from in nature what is called competition release. A species whose distribution is restricted to a small geographical area because of the presence of competitively superior species is found to expand its range dramatically when competing species is removed. Connell’s elegant field experiments showed that on the rocky sea coasts of Scotland, the larger and competitively superior barnacle Balanus dominates the intertidal area, and excludes the smaller barnacle Chathamalus from that zone. In general, herbivores and plants appear to be more adversely affected by competition than carnivores.
Competitive Exclusion Principle
Gause’s ‘’Competitive Exclusion Principle’’ states that two closely related species competing for the same resources cannot co-exist indefinitely and competitively inferior one will be eliminated eventually. This may be true if resources are limiting, but not otherwise. The species facing competition might evolve mechanisms that promote co-existence rather than exclusion. One such mechanism is resource partitioning. If two species compete for the same resource, they could avoid competition by choosing, for instance., different times for feeding or different foraging patterns. MacArthur showed that five closely related species of warblers living on the same tree were able to avoid competition and co-exist due to behavorial differences in there foraging activities.