Parasitism is the biology term used to describe the relation between two different kinds of organisms in which one receives benefits from the other by causing damage to it.
Eg. Mosquitoes, and Plasmodium—the parasite that causes malaria. This is an excellent example of how multiple species can be tied together in complex ecological interactions.
For example, one organism (called a parasite) lives off another (called a host). It may live on or inside the host. A parasite does not help the host. Sometimes it hurts the host, sometimes it does not.
“Cymothoa exigua is a parasitic crustacean of the family Cymothoidae. This parasite attaches itself at the base of the tongue of the Spotted rose snapper, Lutjanus guttatus, with the claws on its front three pairs of legs, and extracts blood. As the parasite grows, less and less blood is able to reach the tongue, and eventually the organ atrophies from lack of blood. The parasite then replaces the fish’s tongue with its own body, by attaching to the muscles of the tongue stub.”
- Without any harm being done, or in the case where some hosts may benefit from the presence of a parasite, in which case we normally speak of:
- mutualism: a situation where two organisms live in some contact and benefit from each others presence. They exchange food or provide shelter or protection, but may still be able to live an independent life.
- symbiosis: a situation where two organisms live in close contact and benefit from each others presence. They have become dependent upon each others presence and are unable to survive independently.
- endosymbiosis: bacteria have invaded the cytoplasm of a eukaryotic host cell. Host cell and bacterium have become dependent upon each other.
- With harm being done.
When one organism lives at the expense of its host we can distinct several situations:- viral infections
- bacterial infections
- parasitic diseases