Difference Between Mutualism and Commensalism

Main Difference – Mutualism vs Commensalism

Mutualism, commensalism, and parasitism are the three categories of symbiotic relationships, occurring between members of two or more species. The main difference between mutualism and commensalism is that in mutualism, both partners of the relationship are benefitted whereas in commensalism, only one partner of the relationship benefits where the other is unaffected.  In parasitism, one partner of the relationship benefits by obtaining nutrients at the expense of the other partner. The symbiotic relationships are maintained in order to achieve basic life requirements such as food, locomotion, shelter, and defense.

Key Areas Covered

1. What is Mutualism
      – Definition, Features, Examples
2. What is Commensalism
      – Definition, Features, Examples
3. What are the Similarities Between Mutualism and Commensalism
      – Outline of Common Features
4. What is the Difference Between Mutualism and Commensalism
      – Comparison of Key Differences

Key Terms: Commensalism, Inquilinism, Metabiosis, Microbiota, Mutualism, Phoresy, SymbiosisDifference Between Stoma and Stomata - Comparison Summary

What is Mutualism

Mutualism is a category of symbiosis where both partners of the relationship benefit. The two partners in a mutualistic relationship are evolved together. Since each partner is a component of the environment, the other partner makes use of it. In that way, both partners benefit from the relationship. Several types of mutualistic relationships can be identified in the environment based on the function. They are nutritional mutualism, shelter mutualism, transport mutualism, pollination mutualism, and defensive mutualism.

Key Difference - Mutualism vs Commensalism

Figure 01: Nutritional Mutualism
(A bird drinks the nectar of a flower while aiding the pollination)

The bee or bird and flower is a mutualistic relationship, which is based on nutritional requirements. The nectar of the flower feeds the bee or bird and other insects. The bee serves as an external pollination agent for the flower. Bacteria in the digestive tract of humans and other animals help the digestion of food while human provides shelter for that bacteria. The nitrogen-fixing bacteria provide nutrients to plants while obtaining a shelter from the roots of the plants. The ants protect acacia plants from browsing animals while the ants obtain food and shelter from the plant.

What is Commensalism

Commensalism is a symbiotic relationship between two organisms in different species where only one partner benefits and the other is unaffected. The unaffected partner in a commensalistic relationship is referred to as the host organism. The commensalistic relationships are based on obtaining nutrients, locomotion, shelter, and support from the host.

Difference Between Mutualism and Commensalism

Figure 02: Pilot fishes with a shark

Four types of commensalism are found; inquilinism, metabiosis, phoresy, and microbiota. In inquilinsm, one organism obtains permanent shelter from the host organism without harming the host. The epiphytic plants growing on trees are an example for inquilinsm. In metabiosis, one organism forms a habitat on the host organism. Hermit crabs using dead gastropods for their protection is an example for metabiosis. In phoresy, one organism attaches with the host organism for transport. Millipedes traveling on birds is an example for phoresy. In microbiota, one organism forms communities within the host organism. The bacterial flora found on the human skin is an example for microbiota. The pilot fishes riding attached to a shark for obtaining food is shown in figure 02.

Similarities Between Mutualism and Commensalism

  • Both mutualism and commensalism are two types of symbiotic relationships within two or more different species where neither species harm.
  • Both mutualism and commensalism are based on obtaining nutrients, locomotion, shelter, defense or support.

Difference Between Mutualism and Commensalism


Mutualism: Mutualism is a type of symbiotic relationship among two or more different species where both species benefit.

Commensalism: Commensalism is a type of symbiotic relationship where only one species benefits and the other is unaffected.


Mutualism: Both species benefit in mutualism.

Commensalism: Only one species is benefitted in commensalism.


Mutualism: Relationship between bees and flowers, digestive bacteria and humans, oxpeckers and zebras, etc. are examples of mutualism.

Commensalism: Hermit crabs using dead gastropods for their protection, millipedes traveling on birds, etc. are examples of commensalism.


Mutualism and commensalism are two categories of symbiotic relationships among two or more different species. Both types of symbiotic relationships are based on either obtaining food, locomotion, shelter, defense, or support. In mutualism, both species benefit. In commensalism, only one species benefits while the other is unaffected. This is the main difference between mutualism and commensalism.


1.”Mutualism.” Encyclopædia Britannica. Encyclopædia Britannica, inc., n.d. Web. . 05 July 2017. 
2.”Mutualism.” McDanile College. N.p., n.d. Web. 05 July 2017. 
3. Helmenstine, Anne Marie. “Benefit Without Harm: Commensalism Explained.” ThoughtCo. N.p., n.d. Web. 05 July 2017.

Image Courtesy:

1.” Hummingbird hawkmoth a” By Yummifruitbat assumed (based on copyright claims) via
2. “Carcharhinus longimanus 1″ By Peterkoelbl assumed (based on copyright claims).via

About the Author: Lakna

Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things

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