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What is Commensalism?

Commensalism, in biology, is a relationship between individuals of two species during which one species obtains food or other benefits from the opposite without either harming or benefiting the latter. The commensal, which is regarded as a species, benefits from the association and gets benefits in the form of shelter, support, nutrients or locomotion from the host species which is unaffected.  

The commensal relation is usually between a bigger host and a smaller commensal. The host organism is really unchanged by the interaction, whereas the commensal species may show great morphological adaptation. This relationship is often contrasted with mutualism, during which both species benefit.

One of the best-known samples of a commensal is the remora (family Echineidae) that rides attached to sharks and other fishes. Remoras have evolved on the very best of their heads a flat oval sucking disk structure that adheres to the bodies of their hosts. Both remoras and pilots fish prey on the leftovers of their hosts’ meals. Other samples of commensals include bird species, like the good egret (Ardea alba), that prey on insects turned up by grazing mammals or on soil organisms stimulated by ploughing. Various biting lice, fleas, and louse flies are commensals therein they feed harmlessly on the feathers of birds and on sloughed-off flakes of skin from mammals.

Population Interaction in the Ecosystem

In an environment, both biotic and abiotic factors are present which are also known as being the biological and physical factors respectively. CO2, water, temperature, air pressure, wind and osmotic balances are the nutrients that are required for a living being. The population can be very well affected by the interactions of the abiotic factors present in the ecosystem. 

Below mentioned are the main modes of interaction between populations;


Competition can be defined as the relationship that takes place when two or more species compete for the same resources that are limited. The resources for which they compete might be food, water, light or any prey. Therefore, here the name is justified, i.e Competition. All these factors are very important for the growth and survival of the organisms. 


This is a relationship where one species depends entirely on the opposite for its food and survival. The species which feeds on other species is named predator whereas the one that's fed upon is named the prey. This complete relationship is named Predation.

Predator is typically stronger than the prey, and hence it consumes prey during its entire life cycle. In some food chains and food webs, a predator can also fall prey as all living organisms develop a kind of defence mechanisms after a certain period of time.

The words ‘predator’ and ‘prey’ aren't always limited to animals. They are implied in the connection between animals and plants also. for instance – rabbit feeding on carrots, bear eating berry and grasshopper and leaf.


Camouflage literally means ‘to disguise’. it's the phenomena where an organism or a species develops structural adaptation that helps them to blend with their surroundings is understood as camouflage. This helps them avoid getting detected by predators.


Symbiosis is a Greek term that means living together. In many relationships, the two or more species or organisms stay dependent on each other for their food and survival for life. This kind of relationship in which one organism lives on another with a mutual but stereotypic behaviour is called symbiosis. 

There are three types of Symbiosis:

  1. Mutualism – where both species are benefitted.

  2. Commensalism – where one species benefits without harming the opposite.

  3. Parasitism – when one species is benefitted by harming the other species. 

Difference Between Mutualism, Commensalism and Parasitism

Basis for comparison





Mutualism is the relationship where both the organisms of distinct species are benefitted.

Commensalism is the relationship where one organism of the two different species gains benefits while the other is unaffected.

Parasitism is the relationship where only one organism receives benefits, while the other is harmed in return.

Kind of relationship



They can be Obligatory or Facultative

Kind of interaction

Mutualism is a positive interaction

Commensalism is a positive interaction

Parasitism is a negative interaction


There is a dependency of the species on each other for food, survival and other mutual benefits

Here, only one species gets benefits, while the other has no effects.

In this relationship, only species get the benefits, while others are harmed.


1. A Sea Anemone and a Clownfish.

2. Pollination by insects or other pollinators.

1. Barnacles growing on whales.

2. Climbers take the support of trees to grow.

1. Salps and Phronima.

2. Cuscuta and the host plant.

FAQ (Frequently Asked Questions)

1. What is Commensalism?

Ans - Commensalism is a relationship between individuals of two species. In this type of relationship, one species obtains food or benefits from the other species without either harming or benefiting the latter. The commensal benefits from the association such as shelter, nutrients, support or locomotion. The host species is unaffected. 

2. What is Camouflage?

Ans - Camouflage is a phenomenon in which a species mimics the environment which helps them avoid getting detected by predators.