What Are The Types Of Interactions Between Organisms?

Entities live in an assemblage of populations having at least two different species who are in constant interaction with each other either directly or indirectly within a specific geographical region in an ecological community. The interaction between species forms the basis for many biological processes in ecosystems such as the food chain and the nutrient cycle.

The nature of these interactions depends upon the environmental conditions and evolutionary aspects in which they exist. There are several classifications of these interactions which are found in different ecosystems. These interactions can be used as a framework in analyzing the ecological community to describe processes that naturally occur which in turn can be used to predict human modifications that may affect the properties and processes of ecosystems. These interactions can be inter-specific(interactions with different species) or intra-specific(interactions between same species). There are five types of interactions between different species as listed below:

1. Competition & Predation
2. Commensalism
3. Parasitism
4. Mutualism
5. Amensalism

Competition And Predation

When one entity hunts another animal to suffice its nutritional requirements, it is referred to as predation. A predator is an entity that hunts its prey. For example, a snake eats a frog. Here snake is the predator and the frog is its prey. Competition, on the other hand, is when populations or even an individual compete for food resources. It is often referred to as exploitative or consumptive competition. When there is a competition for territory it is interference competition and preemptive competition is when they compete for a new piece of territory and have arrived first.

It is an imbalanced type of interaction wherein one entity benefits while the other is neither harmed nor benefited. There are four types of commensal associations.

• Inquilinism – An entity occupies living habitat of another species(burrow, nest)

• Chemical commensalism – A bacteria produces a chemical which nurtures another bacteria

• Phoresy – An organism tentatively attaches itself to another entity for transportation requirements.

• Metabiosis – One entity is dependant on the other for survival


One entity benefits from other entities and is harmed, but not necessarily killed. The entity that is harmed is the host and the one benefited is the parasite. When the host is killed, this type of behaviour is referred to as parasitoidism. These parasites can be living on the surface of the host, often addressed as ectoparasites (fleas, leeches) while endoparasites live inside the host. Endoparasites can be subdivided into intracellular parasites(live inside cells) and intercellular parasites(live in spaces between cells).

Both species involved in the interaction are benefited. These interactions take place in three patterns:

• Facultative mutualism – Species survive on their own under favourable conditions

• Obligate mutualism – One species is dependent for survival on the other

• Diffusive mutualism – One entity can live with multiple partners

These relationships have three purposes:

• Defensive mutualism

• Trophic mutualism

• Dispersive mutualism


In this type of interaction, when one population finds itself in danger the other population is not majorly affected. For instance, Tall and wide plants hinder the growth of comparatively smaller plants. Some plants even secrete substances that repress the growth of nearby plants in order to remove competition.


1. Which of the following lists has ONLY biotic factors?

a) snail, algae, guppy, sunlight
b) temperature, Daphnia (water flea), snail, guppy (fish)
c) snail, guppy (fish), Daphnia (water flea), algae
d) temperature, pH, conductivity, nitrite concentration


2. Temperature, light, air, water, and soil are all _____ parts of the environment

a) Alive
b) Biotic
c) Abiotic
d) Living


3. Lizards and cacti are biotic factors in a desert ecosystem that would rely on which abiotic factors?

a) insects and sun
b) water and insects
c) snakes and temperature
d) water and soil


4. 20. A collection of organisms that belong to different populations but all live in the same area and interact with one another.

a) Population
b) Ecosystem
c) Community
d) Ecosphere


5. A group of populations of two or more species occupying the same geographical area at the same time is called

a) Ecosystem
b) Commensalism
c) Interaction
d) Community


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