Competition occurs when two or more organisms need the same resource and that resource is in short supply. Each competitor reduces the amount available to the others, so competition lowers the survival, growth or reproduction of all those involved.Resources that organisms compete for include:
- Animals: food, water, space or territory, shelter, nest sites and mates.
- Plants: light, water, mineral ions (such as nitrate and phosphate), space and pollinators.Competition can take two forms. In scramble competition every individual gets some of the resource, but when it is scarce none get enough, as when caterpillars strip a plant bare. In contest competition some individuals win the resource and others get none, for example when a bird defends a territory.Ecologists divide competition into two types, depending on who is competing:
- Intraspecific competition: between individuals of the same species.
- Interspecific competition: between individuals of different species.Competition only happens when a resource is limiting. Two species of bird eating the same seeds do not compete if seeds are so plentiful that both have enough. Because a shortage becomes worse as numbers rise, competition is a density-dependent factor. The next two lessons look at each type of competition in detail.
- Animals: food, water, space or territory, shelter, nest sites and mates.
- Plants: light, water, mineral ions (such as nitrate and phosphate), space and pollinators.Competition can take two forms. In scramble competition every individual gets some of the resource, but when it is scarce none get enough, as when caterpillars strip a plant bare. In contest competition some individuals win the resource and others get none, for example when a bird defends a territory.Ecologists divide competition into two types, depending on who is competing:
- Intraspecific competition: between individuals of the same species.
- Interspecific competition: between individuals of different species.Competition only happens when a resource is limiting. Two species of bird eating the same seeds do not compete if seeds are so plentiful that both have enough. Because a shortage becomes worse as numbers rise, competition is a density-dependent factor. The next two lessons look at each type of competition in detail.