[Biology Class Notes] on Commensalism Pdf

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

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. 

Predation

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

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

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