Explain competition in detail.

(N/A) Competition is a potent force in organic evolution.
It is generally believed that competition occurs when closely related species compete for the same resources that are limiting,but this is not entirely true.
Firstly,totally unrelated species could also compete for the same resource.
For instance,in some shallow South American lakes,visiting flamingoes and resident fishes compete for their common food,the zooplankton in the lake.
Secondly,resources need not be limiting for competition to occur; in interference competition,the feeding efficiency of one species might be reduced due to the interfering and inhibitory presence of the other species,even if resources (food and space) are abundant.
Therefore,competition is best defined as a process in which the fitness of one species (measured in terms of its '$r$',the intrinsic rate of increase) is significantly lower in the presence of another species.
It is relatively easy to demonstrate in laboratory experiments,as Gause and other experimental ecologists did,when resources are limited the competitively superior species will eventually eliminate the other species,but evidence for such competitive exclusion occurring in nature is not always conclusive.
Strong and persuasive circumstantial evidence does exist however in some cases.
The Abingdon tortoise in Galapagos Islands became extinct within a decade after goats were introduced on the island,apparently due to the greater browsing efficiency of the goats.
Another evidence for the occurrence of competition in nature comes from what is called competition release.
$A$ species whose distribution is restricted to a small geographical area because of the presence of a competitively superior species,is found to expand its distributional range dramatically when the competing species is experimentally 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 $Chthamalus$ from that zone.
In general,herbivores and plants appear to be more adversely affected by competition than carnivores.