Animal association and interactions among different species

What is population?

A population in ecological terms can be described as a collection of organism belonging to similar species residing in a particular area. A population consists of individual organisms that have the potential to interbreed.

Population Interactions:

 Interaction among organisms of similar species is called intra-specific relationship and the interaction among organisms of dissimilar species is called inter-specific relationship. Depending on the type of relationship, the interactions can be classified as positive and negative.


  1. Positive interaction – This is the type of interaction in which the organisms involved is not harmed in any way and the relationship proves to be beneficial for them. Positive interaction is classified into following types:
  • Mutualism (Symbiosis) – It is a mutually beneficial relationship among individuals of dissimilar species where the organisms involved do not have the capability to live separately. Symbiosis is a synonym of mutualism. The association in this type of interaction is obligatory because the organisms involved are dependent on each other for their existence. The dependence is for shelter, food and transport. Pollination of flowers via butterflies, bees, and moths is an example of mutualism.
  • Proto-cooperation – It is a mutually beneficial association for the organisms involved but it is non-obligatory because the organisms are not dependent on each other for their existence. The relationship between sea anemone and hermit crab is an example of proto-cooperation.
  • Commensalism – It is the association between several organisms in which the organisms involved are not physiologically dependent on each other. The association is such that only one of the organisms is benefited and it is neither harmful nor beneficial for the other. In this type of association where there is continuous contact, the organisms (called commensals) remain attached to their hosts permanently. Epiphytes such as orchids, some hygroscopics and bromeliads which grow on branches of trees are examples of commensals and their association is known as commensalism.

2. Negative interaction – This is the type of interaction in which the organisms involved are affected. Negative interaction is classified into the following types:

  • Amensalism – In amensalism one of the organisms involved in the interaction restricts the other’s effects. The restricting organism is not much benefited. For restricting the organisms secrete allochemics. The secretion of harmful chemicals is known as antibiosis and they are harmful for other organisms. Antibiotics like streptomycin, penicillin, etc are produced by fungi.
  • Competition – It can be described as the demand for the same resource by many organisms belonging to identical species and at similar trophic level. Competition is divided into 2 types:

a)Interspecific competition – The competition occurs among organisms belonging to different species. The competition is not much severe due to lesser needs and different adaptations.

b)Intraspecific competition – The competition occurs among organisms belonging to same species. The competition is much severe due to same kinds of requirements and adaptations. For example cannibalism in snakes and scorpions.
3.    Parasitism – Parasitism is a beneficial relationship for the parasite and harmful for the host. In parasitism the parasite gains benefits from the host. Parasites are divided into 2 types:

i) Endoparasites – These exist inside the host and are prevalent in nature.

ii) Ectoparasites – These exist on the outside or surface of the host and consume living and dead tissues.

4.    Predation – An organism that captures, kills and feeds on organisms of different species is called a predator. The leaves of the pitcher plant consist of a liquid that is used to trap insects.     

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Srirupa Banerjee is the founder & administrator of DNA2Life, She holds Masters Degree from the University of Calcutta. She is a Gold Medalist from the same University. She scored brilliantly in the National Eligibility Test (NET) jointly conducted by the UGC-CSIR, the two foremost educational bodies in India. Srirupa has remained a National Scholarship Awardee all throughout her school and college days. She had a long experience in college teaching. Later she moved on to the world of Information Technology and had years of experience in working with a renowned multinational company.

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