Summary
Interaction in which organisms vie for the same limited resource, intraspecific or interspecific.
In depth
Intraspecific competition acts within a species and regulates population size; interspecific competition between species can lead to exclusion or niche shifts. Types: exploitation (consuming shared resources) and interference (direct combat or chemicals).
Resource competition predicts that the species that can use a resource at lowest level (R*) wins. Interference includes allelopathy in plants. Outcomes depend on environment.
Common mistake: competition does not always lead to exclusion; coexistence is possible with niche differences.
Competition can be exploitative (using up shared resources) or interference (fighting, allelopathy, territoriality). Plants compete for light, water and nutrients; the black walnut releases juglone that inhibits neighbours. Competition leads to character displacement, where traits diverge in areas where species overlap, as in Galapagos finch beaks.
Experiments by Connell with barnacles on rocky shores showed that Balanus excludes Chthamalus from the lower zone, but physical stress limits Balanus in the upper zone, so the realised niche is smaller than the fundamental one. Competition between invasive and native species is a major cause of biodiversity loss.
Key idea: intraspecific competition is usually stronger than interspecific competition when species coexist, which promotes stability.
Frequently asked questions
What is Competition?
Interaction in which organisms vie for the same limited resource, intraspecific or interspecific.
Which area of biology covers Competition, and how advanced is it?
Competition is one of the 54 topics in Ecology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Competitive Exclusion, Limiting Factors, Niche Partitioning.
Can you give an example of Competition?
Red squirrels in Britain have been outcompeted by introduced grey squirrels.
What should I learn before Competition?
Work through the Beginner topics in Ecology first, such as Ecology, Ecosystem, Biotic and Abiotic Factors, then return to Competition. Intermediate topics assume the Beginner vocabulary.
What topics are related to Competition?
The closest topics to Competition are Competitive Exclusion, Limiting Factors, Niche Partitioning, Habitat and Niche. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Competition?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Competition. To practise the whole of Ecology, use the Ecology quiz.
How is Competition different from Competitive Exclusion?
Competition: Interaction in which organisms vie for the same limited resource, intraspecific or interspecific. Competitive Exclusion: Two species competing for exactly the same niche cannot coexist indefinitely. Read both side by side and note what each one explains.
What is a common mistake about Competition?
Competition does not always lead to exclusion; coexistence is possible with niche differences.
How should I study Competition step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Competitive Exclusion and explain the difference aloud. Finally, take the Ecology quiz and come back to this page for any question you miss.