Types of Biotic Interactions in a Food Web

Types of Biotic Interactions in a Food Web – UPSC Environment Notes

The Biotic Interactions is the impact that two species residing in the same community exert on each other. These species may belong to the same or different categories. Biotic Interactions encompass five types: mutualism, competition, commensalism, predation, parasitism, neutralism, and ammensalism. This article aims to elucidate the Types of biotic interaction, essential for UPSC Civil Service exam preparation in the Environment syllabus.

Biotic Interaction- Concept

  • Biotic Interaction: Effect of two species coexisting in a community on each other in ecology.
  • Short-term Interactions: Examples include pollination and predation.
  • Long-term Interactions: Impact extends to factors like extinction, influencing species evolution.
  • Symbiosis: Signifies a prolonged relationship, involving shared resources or common opponents.
  • Indirect Interactions: Mediated by intermediaries like shared resources or common opponents.
  • Ecology and Evolution Significance: Emphasizes the crucial role of short-term interactions, such as predation and pollination, in these fields.

Types of Biotic Interaction


  • Mutualism Definition: Reciprocal relationship where both species benefit.
  • Scope of Relationship: Exists within a species or between different species.
  • Wide Range of Organisms: Involves humans, animals, birds, plants, bacteria, viruses, fungi, etc.
  • Mutual Interaction: All living organisms engage in mutual interactions.
  • Partnership Dynamics: Both host and mutualist benefit without harm to either party.
  • Terminology: “Mutualist” refers to the smaller partner, and “host” refers to the larger participant.
  • Duration of Partnership: Can be either long-lasting or short-lived.


Commensalism characterizes a relationship between members of two species, where one gains food or other advantages from the other without causing harm or providing benefits in return.

  • Defining Commensal: The species deriving benefits in the relationship is termed the commensal.
  • Benefit Types: The commensal may obtain nourishment, shelter, support, or movement from the unaffected host species.
  • Size Dynamics: Typically involves a larger host and a smaller commensal in the relationship.
  • Impact on Host: The contact leaves the host organism relatively unaltered.
  • Adaptation: The commensal species may undergo significant morphological adaptation.
  • Example: The remora (family Echineidae), riding on the backs of sharks and other fish, serves as a well-known instance of a commensal relationship.


Competition is the interaction among organisms or species vying for a limited resource. This dynamic reduces the fitness of both organisms, as the presence of one species impacts the resource availability for the other.

  • Limited Resource: Competition arises when organisms require a resource in limited supply.
  • Fitness Impact: Presence of one species affects the accessible resources, diminishing the fitness of both competitors.
  • Intraspecific Competition: Pertains to competition among members of the same species, a crucial aspect in community ecology.
  • Biological Interaction: Competition is a vital element influencing community structure, species diversity, and population dynamics.
  • Ecosystem Role: Ecological competition within ecosystems contributes to sustaining community structure and promoting species variety.

Predation and Parasitism

In an ecosystem, predation and parasitism represent two forms of interspecific interactions, occurring when individuals from different species engage with one another.

  • Interspecific Interactions: Engagements between individuals from different species within an ecosystem.
  • Negative Interactions: Both predation and parasitism are categorized as negative interactions.
  • Predation Dynamics: In predation, the predator is the active creature, and the victim is passive.
  • Parasitism Dynamics: In parasitism, the parasite is active, and the host is passive.
  • Immediate Impact: Predation leads to the immediate death of the prey.
  • Host Impact in Parasitism: Parasitism does not immediately result in the death of the host organism.
  • Exceptional Cases: In rare instances, the parasite may, however, lead to the death of the host organism.


Amensalism defines a negative relationship between two species, where one species harms or restricts the other without suffering negative consequences itself.

  • Negative Relationship: Amensalism involves one species negatively impacting another without reciprocal harm.
  • Examples: Instances include antibiotic-secreting organisms affecting species inhibited by antibiotics.
  • Modes of Amensalism: The concept is manifested in two modes – Competition and Antibiosis.


In ecology, neutralism denotes a biological relationship where the population density of two species seems to have no discernible effect on each other.

  • Neutral Relationship: Neutralism is characterized by an apparent lack of impact on population density between two species.
  • Examples: Instances include pelicans and cormorants feeding in the ocean, spiders and mantis preying on the same bush’s insects, diverse songbirds coexisting in a woodland, and various microorganisms residing in different human body organs.
  • Symbiotic Relationships: These examples represent forms of symbiotic relationships categorized as neutralism.
  • Study Conclusion: Rigorous examination suggests that true neutralism is unlikely to exist and would be challenging, if not impossible, to establish.


Biotic interactions exert influence on diversification patterns, shaping responses to historical extinction events and non-human animals’ reactions to human ecological disturbance, from bottom left to top left. These interactions are pivotal in determining the diverse patterns of organismal diversity.

FAQs on Types of Biotic Interactions in a Food Web

Q1: Why are biotic and abiotic interactions important?

A: Biotic and abiotic interactions are crucial for ecosystem balance. Biotic interactions involve living organisms, while abiotic interactions involve non-living elements. Together, they shape ecological processes, influencing biodiversity, nutrient cycles, and overall ecosystem health.

Q2: How do biotic factors interact?

A: Biotic factors interact through various mechanisms such as competition, predation, mutualism, and commensalism. These interactions play a vital role in species coexistence, population dynamics, and ecosystem stability.

Q3: What organisms benefit from interactions?

A: Numerous organisms benefit from interactions. Mutualistic relationships, for instance, provide advantages to both parties involved. Additionally, symbiotic associations, where organisms share resources or engage in cooperative behaviors, contribute to the well-being of the participating species.

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