Kinds of Relationships between Organisms

What is Mutualism, Commensalism, Parasitism, Predation, Competition, Cooperation or symbiotic relationship?



  • Mutualism is a biological interaction between two organisms.
  • Most mutualisms are facultative, meaning the partners can successfully live apart. However, some mutualisms are so intimate that the interacting species can no longer live without each other; they have a mutually obligate interdependence.
  • Examples:
    • As the bee or butterfly sips nectar from the flower, pollen gains sticks to their hairy legs and other parts of their body. When the insects goes to another flower to get nectar, it drops some of the pollen gains into the flower.
    • The heron at the back of the carabao feeds on the ticks that suck the blood of the carabao.  The heron gets food by eating the ticks.  At the same time, the carabao gets cleaning of its parasites.  Both heron and the carabao benefit from this kind of relationship.




  • Commensalism is a relationship wherein one participating organisms is benifited while the other is neigther helped nor harmed.
  • The term derives from the English word commensal, meaning "sharing of food" in human social interaction, which in turn derives from the Latin com mensa, meaning "sharing a table".

  • Examples:

    • Orchids and some kinds of fern are aerial plants.  They usually grow on trunks or branches of trees.  These plants get moisture and nutrients from the bark of the tree.  They also use the tree for support because they do not have stems.  The orchids or ferns do not seem to harm or help the tree.

    • The barnacles are shelled animals that cannot move on their own.  They attached themselves to other animals like crabs or whales.  The barnacles get transportation and a steady supply of food as the whale moves through the ocean.  The whale on the other hand, is generally not affected by this kind of interaction.




  • Parasitism is a relationship wherein an organism gets the benefit and the other is harmed.
  • In this relationship, the host may become weak but does not usually die.  If the host dies, the parasites may also die.
    • Parasites are organisms that live inside or outside the body of another organisms and feed on it.
    • Host is the provider of food and shelter for the parasite.
    • Ectoparasites are parasites that live outside the body of the host.
    • Endoparasites are parasites that live inside the body of the host.
  • Example:
    • Fleas and dog – fleas are insects that suck blood from the body of the dog.  They also live on the body of the dog.
    • Mosquito bites human to suck blood.
    • Hook worms or round worms on human digestive tract.




  • Predation is a relationship wherein a smaller animal is killed and eaten by a bigger animal.

    • Predator – the animal that feeds on another animal.

    • Prey – the animal that is eaten.

  • Example:

    • The hawk catches the fish for food.

    • Frogs feed on insects.

    • Lion hunt deer for food.




  • Competition is a relationship wherein two or more organisms need the same thing in order to survive.  It may exist among organisms of the same kind or of different kinds.

  • In this kind of interaction, the organisms fight for a common resources in order to survive.

  • The common resources could be food, water, sunlight, shelter or space, and other things.

  • Example:

    • In a rice field, rice plants compete with each other for water, minerals, space, and sunlight.  At the same time, the rice plants compete for the same resources with the weeds that grow among them.
    • Both vegetable plants and the weeds need sunlight, water, and minerals in order to survive.
    • Dogs and cats need same kind of food and may fight over it.




  • Cooperation/Symbiotic relationships are relationships where two organisms of different species live and work together, each one of them benefiting from mutual cooperation.
  • The relationship between two entities that need each other to survive and prosper.
  • Example:
    • Both the human as well as the animal kingdom is dependent on the oxygen produced by the plant kingdom. Conversely, plants depend on animals and humans for carbon dioxide to prepare their food.
    • The bee and the flower. Bees get nectar from flowers. Pollination also takes place when the bee flies from one flower to another.


25 Responses to Kinds of Relationships between Organisms

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