Discovery Science: Ecology – Populations – Competition

Earth Science: Ecology – Populations – Competition

The intra- and interspecific competition—that is, the contest among organ- isms for limited resources, such as food and living space—are significant biotic environmental factors that often have a large influence on biomass.

With intraspecific competition, the individuals of a species are in direct competition for biotic and abiotic resources, while with interspecific competition there are two or more species that have similar requirements. Within this context one refers to the totality of all biotic and abiotic environmental factors important for a species as the ecological niche of that species.

This term, however, does not describe space but rather respective interactions. The occupation of various ecological niches within the same ecosystem is regulated by interspecific competition: the competitive behavior increases the closer the resemblance between two species. In order to avoid such competitive situations if possible, many species have developed special adaptations to their environments.

An example of this is niche occupancy, which is an effective method to avoid interspecific competition and there- fore facilitates the coexistence of many species within the same biotope. Niche occupancy can occur through several different factors, for instance through the variation of main activity periods (day and night activity), diverse food particle sizes, searching for food at various sites, different temperature optima, distinct times for reproduction and for brood care, and so on.

Occasionally, niche occupancy can occur within a species that lowers intra- specific competition (intra- specific competition widens the niche, inter-specific reduces the scope of competition). According to the competitive exclusion principle, there can never be two species with identical ecological niches in the same environment. However, it is possible that different, geographically separated species can occupy comparable ecological niches.

The development of similar forms, organs, and modes of life in this case is called convergence (for example, the similar body forms of fish and aquatic marine mammals, such as dolphins).


A good example of niche occupancy is food acquisition among ducks.

The gray goose grazes on land for terrestrial plants; the teal searches for tiny plant food along the water surface; mallard ducks, northern pintails, and mute swans dabble for water plants, worms, and small crustaceans; while the Goosander hunts for free-swimming food organisms.

Varying neck lengths allow species to reach different depths.


BIOLOGICAL BALANCE Mutual competition, recruitment and departure of individuals, and the dependency relationship among species leads to the establishment of a dynamic ecological equilibrium.