Commensalism - Definition, Types, Examples and Relationship
Commensalism is a long-term biological interaction where one species benefits while the other is unaffected. Commensalism, definition , types and examples notes are provided below for NEET aspirants.
Krati Saraswat31 May, 2025
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Commensalism: Commensalism is a long-term biological symbiosis in which one species benefits while the other is unaffected. This contrasts with mutualism, in which both species benefit. Amensalism, in which one is harmed while the other is unaffected, and parasitism, in which one benefits at the expense of the other.
In commensal relationships, the benefiting species, also known as the commensal, receives nutrients, shelter, support, or locomotion from the host species, which is largely unaffected. The commensal is smaller than the host, and while the host remains unchanged, the commensal may show significant structural adaptations to suit its lifestyle. For example, remoras attach themselves to sharks and other fish, feeding on their hosts' faeces, whereas pilot fish feed on leftovers from their hosts' meals. Furthermore, many birds perch on large herbivorous mammals or consume insects disturbed by grazing mammals. Commensalim NEET Biology Notes for the NEET exam are provided in the article below.Commensalism Definition
Commensalism is a form of symbiotic relationship in which one organism, known as the commensal, benefits from the association . In contrast, the other organism termed the host, neither gains nor suffers harm. The commensal derives advantages such as food, shelter, or transportation from the host. Although commensalism is a one-way relationship, it significantly impacts ecosystems. For example, remoras, which attach themselves to sharks, help to keep them clean by eating parasites and dead skin.Commensalism Types
Commensalism is a symbiotic relationship in which two species coexist, with one benefiting while the other remaining unaffected. The following are four types of commensalism:Phoresy: In this case, one organism attaches itself to another for transportation. The remora fish is a prime example, as it rides on sharks or other large fish. The remora gains transportation and easy access to food scraps left by the host. Inquilinism: One organism resides in or on another for shelter or protection. A classic example is the hermit crab, which lives in the empty shell of a dead snail. The snail does not change, but the hermit crab is protected.
Metabiosis: This form involves one organism altering the environment to benefit another. The dung beetle, for example, decomposes dung, allowing mites and bacteria to flourish. The beetle benefits from the food source in the dung, while the mites and bacteria benefit from the habitat.
Microbiota: This refers to the collection of microorganisms living on or inside the body of a human or animal. The microbiota can benefit the host by aiding in digestion, protecting against pathogens, and producing vitamins. In turn, the microbiota benefits from the host's provision of food and shelter. It is important to recognize that the distinction between commensalism and other types of symbiotic relationships can be ambiguous at times. Some scientists believe that the relationship between humans and gut bacteria is mutualistic, with both parties benefiting from the association.
Commensalism Examples
Commensalism is a form of symbiosis where one organism benefits while the other remains unaffected. Here are several examples:Sharks and Remora (Suckerfish): Remoras, also known as suckerfish, attach themselves to sharks and other large fish using a suction disc on their heads. This allows them to travel long distances with minimal effort and feed on scraps of food left behind by the shark. The shark is not affected by the presence of the remora.
Hermit Crabs and Shells: Hermit crabs use the empty shells of dead mollusks for protection. The crab benefits from the protection offered by the shell, while the shell itself is not affected.
Cattle Egrets and Cows: Cattle egrets often follow herds of cows or other grazing animals. As the cows graze, they stir up insects from the grass. The egrets then swoop down to catch the insects, benefiting from the cow's activity without causing harm to the cow.
Barnacles and Whales: Barnacles are small crustaceans that attach themselves to whales and other marine animals. The barnacles benefit from the whale's movement, which allows them to filter more food from the water. The whale is largely unaffected by the presence of the barnacles.
Epiphytes and Trees: Epiphytes are plants that grow on other plants, such as orchids that grow on tree branches. The epiphyte benefits from the support and elevation provided by the tree, but the tree is not affected by the presence of the epiphyte. These examples illustrate how commensalistic relationships contribute to the diversity of species in a habitat without causing harm to either species involved.
Commensalism in Plants
Commensalism is a type of symbiotic relationship between two organisms where one organism benefits from the other organism, while the other organism is neither helped nor harmed. In the plant kingdom, there are several fascinating examples of commensalism.- Epiphytes and Host Plants: Epiphytes are air plants that grow on other plants, such as trees, for physical support. They get their nutrients from the air and rain, and they do not harm the host plant in any way. Some well-known epiphytes include orchids, bromeliads, and mosses.
- Vines and Trees: Some vines use trees for support as they grow towards the sunlight, but they do not take any nutrients from the tree. This relationship benefits the vine without harming the tree.
- Seed Dispersal: Seed dispersal can also be an example of commensalism. Certain plants, like burdock, have fruits or seeds that attach themselves to animals' fur. This hitching a ride helps the plant disperse its seeds to new locations, but it doesn't necessarily benefit the animal.
Commensalism in Microbiology
Commensalism is a type of symbiotic relationship between microorganisms in which one organism benefits from its association with another, while the other organism is unaffected, neither harmed nor benefited. This stands in contrast to mutualism, where both organisms benefit, and parasitism, where one organism benefits at the expense of the other. Many examples of commensalism can be found in microbiology, including the following:- Skin microbiota: The human skin hosts various bacteria, some of which are advantageous. These commensal bacteria aid in safeguarding the skin against harmful pathogens by competing for resources and producing antimicrobial substances.
- Gut microbiota: The human gut accommodates trillions of bacteria, many of which are commensal. These commensal bacteria assist in food digestion, vitamin production, and immune system regulation.
- E. coli: Although certain strains of E. coli can cause diseases, many strains coexist commensally in the intestines of humans and animals without causing harm. In fact, these commensal E. coli bacteria help in controlling harmful pathogens.
Commensalism vs Mutualism
Commensalism and mutualism are two types of symbiotic relationships between organisms. While commensalism benefits one organism without affecting the other, mutualism benefits both organisms involved.| Commensalism vs Mutualism | ||
|---|---|---|
| Aspect | Commensalism | Mutualism |
| Benefit Outcome | One organism benefits, other is unaffected | Both organisms benefit from the relationship |
| Impact on Other Organism | Neutral, no harm or benefit | Positive impact, both organisms benefit |
| Example | Barnacles attaching to whales | Bees pollinating flowers |
| NEET Exam Important Links | |
|---|---|
| NEET Syllabus | NEET Biology Diagrams |
| NEET Biology MCQ | NEET Biology Chapter wise Weightage |
| NEET Biology Notes | NEET Previous Year Question papers |
Commensalism FAQs
Q 1. What is commensalism and what are some examples?
Ans. Commensalism is a type of relationship between two organisms where one organism benefits, and the other is neither helped nor harmed. An example of commensalism is the relationship between small birds and large grazing herbivores.
Q 2. What is the difference between commensalism and amensalism?
Ans. Commensalism is a relationship where one organism benefits while the other is unaffected. In contrast, amensalism is a relationship where one organism is harmed, but the other is neither helped nor harmed.
Q 3. What is the difference between commensalism and mutualism?
Ans. Mutualism is a relationship where both organisms benefit. In commensalism, one organism benefits while the other is unaffected. Parasitism, on the other hand, is a relationship where one organism benefits while the other is harmed.
Q 4. Is symbiosis an example of commensalism?
Ans. Symbiosis is a close relationship between two species, and it can include commensalism, mutualism, or parasitism. In commensalism within symbiosis, one species benefits while the other is not affected.
Q 5. What does commensalism mean in biology?
Ans. In biology, commensalism refers to a relationship between two species where one species benefits, usually by obtaining food or other benefits, from the other species without harming or benefiting it.
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