The three major types of symbiosis are mutualism, where both species benefit, commensalism, where one species benefits and the other is unaffected, and parasitism, where one species benefits and the other is harmed. Symbiotic relationships can occur within an organism's body or outside of it.Continue Reading
Examples of mutualism include the relationship between single-celled organisms or animals that incorporate algae into their bodies. They give the algae necessary nutrients, and in return receive chemical energy from the photosynthetic algae. Animals that have this sort of relationship include some sponges, sea anemones and clams.
Examples of commensalism include remora fish attaching to the bodies of sharks and eating scraps of food that escape their jaws, and barnacles living on the jaws of whales with a similar feeding strategy. Plants have commensal relationships as well, such as many orchids that grow on taller plants and benefit from the additional sunlight they obtain, without actually stealing nutrients from the host plant.
Parasitic relationships are many, and parasites include all disease-causing organisms. This category also includes insects such as fleas that suck the blood of hosts externally. Parasitism is a very efficient strategy for organisms, and parasites often lose many of the features of non-parasitic life forms, instead relying on their hosts for many of the functions of life.Learn more about Biology