Competition in biology is an event where organisms require resources that are in limited supply. This interaction always results in lower fitness for both parties involved because one organism's existence directly cuts into the resource pool of the other.
Interference competition involves physical fighting or aggression between individuals to claim territory or resources. Exploitation competition occurs when organisms indirectly deplete a shared resource without ever meeting face-to-face, often favoring those who claim resources first.
Robert MacArthur and E. O. Wilson published The Theory of Island Biogeography on the 2nd of May 1967. Their work laid the foundation for r/K selection theory which relates to traits promoting success in particular environments.
Georgy Gause proposed the Competitive exclusion principle in 1934 within his book The struggle for existence. He observed that species cannot coexist if they have identical ecological niches requiring the same resources.
Character displacement describes the observation that traits become more different when species live in the same area. When Geospiza fortis and Geospiza fuliginosa live on the same island, individuals with intermediate-sized beaks face intense competition while those with small or large beaks have greater survival rates because they specialize in particular seed sizes.