Competition Interaction- Definition and Types with Examples

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Competition Definition

Competition is a biological interaction between two or more organisms of the same or different species where the species compete with each other for different resources.

  • Most of the competitive interaction occurs for the need of food sources that occur in a limited supply when compared to demand. However, organisms might compete for other resources like shelter, light, and substrate.
  • The interaction often leads to a change in fitness between the organisms that share the same resources.
  • Competition is one of the most important biological factors that determine the community structure in an environment.
  • Between the two competing organisms, the weaker organism has to either adapt or die out while the stronger organism obtains the resources.
  • One of the major factors that influence the extent and duration of the competition is the density of the individuals or the number of organisms residing in an area. If the number increases rapidly, the available resources begin to deplete, leading to ecological competition.
  • Besides, the degree of competition also depends on the sharing of resources by different organisms. If two different groups of organisms utilize the same resources, the competition for that resource will be more intense.
  • Even though it is believed that competition is often advantageous to the stronger species as the weaker species tend to extinct due to the lack of resources, there are instances when there is a decline even in the population of the stronger species.
  • The process can, however, can be changed due to evolution or other environmental factors that can totally flip the situation.
  • The competition was considered one of the major driving forces for evolution by Darwin. He described evolutionary adaptation influences by competition in one of his most famous examples in Darwin’s finches of the Galapagos Islands.
  • Besides affecting the structure of a community, the competition also puts evolutionary pressure on the development of adaptations in a community.
Competition Interaction
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Types of Competition

Competition can be divided into different types on the basis of different factors. On the basis of the taxonomical relationship, competition is divided into the interspecific and intraspecific competition. On the basis of mechanism, competition is divided into interference, exploitative and apparent competition. On the basis of influence, competition is divided into the direct and indirect competition. Some of the competitive interaction belongs to more than one of these classifications.

1. Intraspecific competition

  • Intraspecific competition is a type of competition between the members of the same species that compete for limited resources.
  • Intraspecific competition can be intense when the population of a species is high as the individuals have virtually identical resource requirements.
  • Intraspecific competition is symmetrical as it involves organisms of similar size competing for the same resources.
  • This type of interaction often leads to the reduction in fitness in both individuals bit the fitter individual usually survives and reproduces.
  • Intraspecific competition can involve both direct and indirect interactions. Direct interactions occur between species occupying the same niche or community, but indirect interactions occur between the same species occupying a different niche.
  • Intraspecific competition is an important regulator of the population size and can also act as a selective factor for evolution.

Example- Plants

  • Different plant species produce various types of chemical substances that discourage other plants of the same species from growing around them.
  • The competition between organisms is usually for space, nutrients, and water around the plants.
  • The plant produces chemical substances like phytotoxins that are harmful even against the organisms of the same species.

2. Interspecific competition

  • Interspecific competition is a type of competition between two individuals of different species competing for the same resources.
  • Interspecific competition is often asymmetric as the individuals are of different sizes with substantial differences in their abilities.
  • Interspecific competition can also be intense if the population of species with similar ecological lifestyles and nutritional requirements increases.
  • This interaction often leads to the reduction in the population of the weaker species, whereas the stronger species survive and continue to reproduce.
  • Interspecific competition is often more fierce than intraspecific competition as two distinct species often differ in fitness which influences the extent of competition.
  • Interspecific competition is an important factor that regulates ecological communities and also acts as an agent of natural selection.

Example- Corals

  • Corals are found at the base of oceans where they line rocks and compete with other species of the ecosystem.
  • These corals filter organic material present in the water as well as various autotrophic bacteria to complete their energy needs.
  • They also compete with other aquatic organisms like fishes for the availability of nutrients and sunlight.
  • They cover large surfaces of the ocean bed in order to obtain enough sunlight for the autotrophic bacteria.

3. Direct and Indirect Competition

  • Direct competition is an interaction where the species living in an ecosystem directly influence each other by affecting the availability of resources in the ecosystem.
  • Indirect competition is a form of competition where the species influence the availability of resources indirectly. The species involved in indirect competition usually exist in different ecological niches.
  • Direct and indirect competition can be observed in both interspecific as well as intraspecific competition.
  • These types of interactions allow studies on the behavior of the species and their lifestyles.

Example of Direct competition- Animals

  • Direct competition in animals can be observed in the case of zebras residing in the same ecological niche.
  • The zebras compete with each other when the grass and leaves in the environment become scarce.

Example of Indirect competition- Animals

  • Indirect competition can also occur between zebras occurring at different but related ecosystems.
  • Zebra present near the pond might affect other zebras that occur away from the pond by decreasing the amount of water in the river. This is a form of indirect competition where the species do not interact with each other but are related by means of a resource.

Read Also: Predation Interaction- Definition and Types with Examples

4. Interference, Exploitation, and Apparent competition

  • Interference competition is a type of competition where the competing individuals directly influence the process of foraging, reproduction of others, or prevent the establishment of the species in an environment. Interference competition involves fighting, stealing, and combat among species to obtain resources.
  • Exploitative competition is a form of indirect competition where the species are connected by a common limiting resource that acts as an intermediate. The common resource can be space, water, or other similar resources.
  • Apparent competition is also a type of indirect competition where both the competing species are preyed upon by the same predator. For example, if species A and B are preyed upon by predator C, the increase in population A might cause a decrease in the population of B as predator C feeds on species A and become more fit which then affects the population of species B.

Example of interference competition- Flamingos

  • Interference competition can be observed in flamingos where the paired flamingos are more aggressive towards single birds for food and survival.
  • The paired flamingos directly interact with a single flamingo and might indulge in fights to protect their mates as well as offspring.

Example of exploitative competition- Spiders

  • Exploitative competition can be observed in the spider population composed of young spiders.
  • When the population density increases and the food resources decrease, it causes a reduction in the growth of new spiders.
  • Even though no direct interaction occurs between young spiders, the number of fewer fit spiders tends to decrease. The fitter species feed on the available nutrients resulting in even less availability to weaker individuals.

Example of apparent competition- Skinks

  • The population of skins in an area decreases after the introduction of rabbits.
  • It is because both the skinks and rabbits are preyed upon by ferrets. The introduction of rabbits to the area causes the immigration of ferrets to the same area.
  • Thus, the ferrets feed on both the skinks and the rabbits for food, reducing the population of both species.

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About Author

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Anupama Sapkota

Anupama Sapkota has a bachelor’s degree (B.Sc.) in Microbiology from St. Xavier's College, Kathmandu, Nepal. She is particularly interested in studies regarding antibiotic resistance with a focus on drug discovery.

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