Commensalism: Definition, Examples, Facts, Topics, Relationships

Commensalism Definition

Commensalism is a kind of symbiosis where one organism gains or is favoured, and the other is unaffected and has neither advantage nor disadvantage.

• Organism 1: +

• Organism 2: 0

In commensalism, the organism that gains an advantage, often in the form of food, shelter or transportation, has no negative impact on the host organism or may offer some minor service to the host organism. This invites a clear difference from mutualism, where both organisms benefit; parasitism, where the predator benefits and the defended gains nothing; and amensalism, where the defender is harmed, but the defender is unharmed.

Some examples of commensal relationships are the barnacles that stick on the whales for transport, the epiphytes that grow on trees, and some bacteria that just reside on the human skin without being parasitic. Commensalism teaches people that the level of interdependence in the natural world is not rigid and that the influence two species can have on each other can be significantly different.

Examples of Commensalism in Ecosystems

Commensalism examples are found in terrestrial ecosystems, marine ecosystems, and the human body. These relationships show how one organism benefits while the host is unaffected. The examples are listed below:

Terrestrial Ecosystems (Birds & Trees, Epiphytes)

Birds and trees

Some species have the ability to make a tree their home without damaging that tree in the process. They make their nests in trees. It offers a firm base and a source of shelter for the birds and a place where they can lay eggs.

Epiphytes on rainforest trees

The smaller plants do not need to be rooted in the soil. They live in the trees and obtain both support and light. For example, orchids, bromeliads, ferns and others. Epiphytes do not damage the host trees and may be beneficial to the host by helping to retain moisture.

Marine Ecosystems (Barnacles & Whales, Remoras & Sharks)

Barnacles on whales

Barnacles adhere to large animals such as whales, and feed with the help of the host’s activity and water rich in nutrients. Barnacles have very little impact on the bodies of the whales and minor skin irritation may occur only when the whales’ skin is heavily infested.

Clownfish and sea anemones

Clownfish form alliances with sea anemones, as the stinging elements present on the tentacles of the sea anemones provide protection from predators. In return, the sea anemones benefit from feeding on the foods brought to them by the clownfish and cleaning the tentacles.

Human Body (Skin Flora, Gut Microbiota)

Skin flora

Skin microbiota, or skin flora, are the microorganisms that are present on the human skin, which include bacteria, fungi and many more. The favourable type of bacteria also originates on the skin and helps counterbalance pathogenic microorganisms in terms of habitat and nutrition, thus protecting the skin from infections.

Gut microbiota

Gut microbiota refers to the composition of bacteria and other microorganisms that reside in the human gut, and their number approximates trillions. As such, these microorganisms help in digestion, the production of vitamins, and the regulation of the immune system. In turn, they get to support a generally healthy nutrient environment of the gut.

Types of Commensalism

The types of commensalism explain how one organism benefits while the host remains unaffected. Major forms include inquilinism, phoresy, and microbiota. These commensal relationships show ecological adaptations. The types of commensalism is described below-

Inquilinism

Inquilinism, where one organism occupies the home of another organism and does not benefit or harm the host organism, is the third type of parasitism.

Examples: Sessile animals live on other animals. For example, barnacles are crustose animals that attach themselves to a larger animal and derive their nutrition from the surroundings without harming the host. Barnacles are parasites which affix themselves to a whale or other sea creature and rely on it for mobility and feeding rights, but do not harm the host.

Phoresy

Phoresy is one of the types of mutualistic relations where one species utilises the other to get from one place to another.

Examples: Microorganisms change locations by moving from one place to another on insects or small animals or from one food plant to another. Remoras anchor themselves to sharks or large fish and feed off what is attracted by the motion of the host and pieces of food disturbed by the creature.

Microbiota

Microbiota involves microorganisms that are present on or within larger animals but do not harm the animal.

Examples: The stomach and intestinal bacteria are involved in the process of digesting feed and synthesising useful products with the help of available nutrients within the host organism. Skin microbial communities encompass bacteria and fungi that live on the skin, act as anti-pathogens and play a role in skin health.

Case Studies in Commensalism

Commensalism case studies show real-world ecological interactions where one species benefits while the host is mostly unaffected.

Oxpecker and Large Herbivores

Earlier, the interaction remained on the verge of mutualism and commensalism between the two. Oxpeckers benefit from feeding on the skin of large herbivores to remove the ticks and parasites that may be infesting the skin, and at the same time, the oxpecker would peck on the blood oozing from the wounds of the herbivore.

Newer studies have established that the association is complex. Hence, oxpeckers mainly help herbivores by removing ectoparasites but sometimes harm them slightly. Such dynamics clearly illustrate the presence of more positive than negative interactions with the hosts, which are rather reciprocal and depend on the hosts’ and environmental conditions.

Human Gut Microbiota (Balance with Pathogenicity)

The human gut microbiome is trillions of microorganisms which help in digestion, synthesis of vitamins, and immune responses. Imbalances in the composition of the bacterial communities living in the gut, resulting from multiple factors – the diet in particular, or taking antibiotics, can cause diseases like inflammation and metabolic disorders. The field of commensalism and pathogenicity is based on the observation that some microorganisms are capable of living with their host in a mutually non-harmful manner.

Importance of Commensalism in Ecology and Health

Commensalism plays an important role in maintaining balance in the ecosystem. It allows one species to benefit by providing food, shelter or transport without affecting the other host. This interaction increases the coexistence of the different species, showing how species can share resources and habitats.

In human health, microorganisms such as skin flora and gut microbiota provide indirect benefits to the body. They prevent the growth of harmful microbes by occupying space and resources. For example, gut bacteria help in digestion and the production of vitamins. This knowledge is essential in assessing the health hazards, sustaining the control of microbes in environments and in people’s anatomies.

Population Interactions NEET MCQs (With Answers & Explanations)

The high-yield topics from Commensalism that should be focused on for exams are:

• Types of Ecological Interactions

• Types of Commensalism (Inquilinism, Phoresy, Microbiota)

• Examples in Ecosystems

• Ecological Benefit and Importance in health

Practice Questions for NEET

Q1. Which connection is described by an orchid growing as an epiphyte on a tree?

1. Mutualism

2. Commensalism

3. Parasitism

4. Ammensalism

Correct answer: 2) Commensalism

Explanation:

A commensal plant is an orchid that grows on an epiphyte. Epiphytes grow on trees to get air and sunshine while causing no harm to the tree. A fern is another epiphyte that grows on trees.

The term "commensalism" refers to a connection in which one organism benefits while the other is neither benefited nor hurt.

Orchids grow on mango trees to obtain appropriate light and other benefits, but they do not take nutrients from the mango tree. As a result, the tree is neither injured nor benefited.

An epiphyte is a plant that lives on a limb of a mango tree, like an orchid. Epiphytes are plants that grow on other plants but do not rely on them for nourishment.

As a result, the place of blue and red colours mixed and a mango seedling is an instance of commensalism, at which point individual class benefits while the difference is honest.

The orchid benefits from the interaction described above because it receives assistance, whereas the mango tree is unaffected.

Hence, the correct answer is option 2) Commensalism.

Q2. Polyploidy states:

1. Occurrence of haploid set of chromosomes

2. Occurrence of diploid set of chromosomes

3. Occurrence of more than a diploid set of chromosomes

4. None of the above

Correct answer: 3) Occurrence of more than a diploid set of chromosomes

Explanation:

When an organism has more than two sets of chromosomes, it is said to be polyploid. Being diploid means that an organism typically has two sets of chromosomes, one from each parent. Multiple sets, such as triploid (3 sets), tetraploid (4 sets), or even higher numbers, are a feature of polyploidy. This can result in bigger, more active organisms and can occur naturally or be generated in plants. Many polyploid crop plants, such as strawberries and wheat, are examples.

Hence, the correct answer is option 3) Occurrence of more than a diploid set of chromosomes.

Q3. Predation, parasitism, and commensalism have the following things in common:

1. The interacting species coexist close together.

2. The interacting species suffer.

3. One of the interacting species gains.

4. One of the interacting species maintains its neutrality.

Correct answer: 1) The interacting species coexist close together

Explanation:

The interdependent species that engage in predation, parasitism, and commensalism coexist near one another.

The fact that interacting species coexist nearby is a frequent characteristic of predation, parasitism, and commensalism. Commensalism is a kind of interaction where one species benefits and the other is left unaffected.
The epiphyte benefits, while the host is unaffected. The two species continue to interact and associate closely with one another. Predation is a harmful relationship in which the predator gains an advantage over the prey. The two species continue to interact and associate closely with one another. The host is injured and the parasite benefits from parasitism, which is a negative relationship. The two species continue to interact and associate closely with one another.

Hence, the correct answer is option 1) The interacting species coexist close together.

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