Difference Between Mutualism and Commensalism

Symbiosis is the most crucial biological process required in the ecosystem. It is the prime process that instigates evolution.


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Lactobacillus and Humans are the best examples of a symbiotic relationship. Our human body has thousands of bacteria without which we cannot survive.

The organisms that undergo the process of symbiosis are called Symbionts. If the symbionts are living on the surface of the other organism it is called, ectosymbiosis.

When talking about Symbiosis, there are three major types of Symbiotic Processes. Mutualism, Commensalism and Parasitism.

Mutualism and Commensalism shall sound similar in their interaction but there are differences between the two.

Key Takeaways

  1. Mutualism is a symbiotic relationship between two organisms in which both species benefit from the interaction, such as bees pollinating flowers while gathering nectar.
  2. Commensalism is a symbiotic relationship where one organism benefits without affecting the other organism, such as barnacles attaching to a whale for transportation without harming the whale.
  3. The key difference between mutualism and commensalism is the outcome for each organism involved; in mutualism, both organisms benefit, while in commensalism, one organism benefits without affecting the other.

Mutualism vs Commensalism

The difference between Mutualism and Commensalism is that during the interaction all the organisms or the species involved in Mutualism are benefitted while in Commensalism one organism is benefitted while the other is neither harmed nor benefitted.

Mutualism vs Commensalism

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Comparison Table

Parameter of ComparisonMutualismCommensalism
Meaning/ DefinitionProcess of interaction in which the organisms that are involved in the interaction are benefitted.Process of Interaction in which one organism is benefitted while the other is not benefitted and also not harmed.
BenefitThere is a mutual benefit among all the organisms involved.Only one organism is benefitted in this interaction.
Type of relationshipObligatory RelationshipNon-Obligatory relationship
Major TypesNutritional, Defence, Transport and ShelterTransport, Shelter, Food
ExamplesThe interaction between bee and the flower, Bacteria and Human BeingsRemora and Shark, Aspergillus and Humans


What is Mutualism?

Mutualism is a symbiotic process where two or more organisms interact very closely and have mutual benefits. It is indeed considered as a positive interaction between the organisms.

Mutualism is for many reasons, they may be categorized as

  1. Transportation Mutualism
  2. Nutritional Mutualism
  3. Shelter Mutualism
  4. Defence Mutualism

In all the above processes, whichever the organisms interact will be benefitted. The relationship is considered Obligatory and both the organisms are required for their survival.

This type of ecological interaction is considered common. Examples can be cited as

  1. Animals pollinating flowering plants
  2. Humans and Bacteria

Mutualism is also considered to be the most critical symbiotic process for the terrestrial ecosystem. It is observed 48% of plants rely on Fungi and this happens through Mutualism only.

At the same time, the animal seed-dispersing mutualistic process accounts for up to 90% of the evolution of the world.

Mutualism is categorized based on the interactions the organisms have between them.

  1. Service and Resource Relationship: This is by far the common mutualistic relationship.
  2. Service and Service Relationship: This is rare to find where organisms involved relying on each other’s services.

Mutualism helps in the survival of organisms as well as growth. It is one of the critical processes to induce evolution.


What is Commensalism?

Commensalism is a symbiotic relationship where two or more organisms are involved. Commensalism is a process where one organism is benefitted while the other is unaffected.

That means to say, the organism is neither harmed nor benefitted. Commensalism is common due to a few factors

  1. Transport Commensalism
  2. Shelter Commensalism
  3. Food Commensalism
  4. Defence Commensalism

The organisms that involve in such interactions are called Commensals. It is generally observed that Commensalism takes place between a smaller commensal and a larger one.

As per the process, the host, that is the bigger commensal remains unaffected while the smaller commensal gets benefitted in one way or the other.

Like Mutualism, Commensalism has also different types

  1. Inquilinism: An interaction where the smaller commensal finds a permanent shelter in the host
  2. Metabiosis: It is an interaction where the smaller commensal makes use of the dead animal as host to survive.
  3. Phoresy: It is the interaction where small commensal utilizes the larger one for transportation purposes.

The experts always feel that explaining commensalism is difficult as the process of one organism not affected is practically not true. The host also undergoes morphological adaptation during the interaction.


Main Differences Between Mutualism and Commensalism

  1. The main difference between Mutualism and Commensalism is the process of interaction. The Mutualism is a symbiotic process where both the symbionts are benefitted while commensalism is an interactive process where one organism is completely benefitted while the other is not affected at all.
  2. The process of interaction for Mutualism is considered ‘Obligatory’ for the mutual obligation the organisms have while the Commensalism is called ‘Non-Obligatory’ interaction.
  3. Mutualism establishes benefits for all the organisms involved, while commensalism does not exhibit any such characteristics. It is only one organism that is benefitted.
  4. Nutritional Benefits are gained in the Mutualism process while Commensalism is more for a shelter and transport based interaction.
  5. There may be a complete morphological adaptation of the organisms that might happen or give rise to a whole new organism or a species through Mutualism while Commensalism does not give rise to any new species and their morphological adaptation are also limited.

  1. https://www.srs.fs.usda.gov/pubs/ja/ja_hofstetter002.pdf
  2. https://www.journals.uchicago.edu/doi/abs/10.1086/283384

This Article has been written by: Supriya Kandekar

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