Endosymbiosis is a mutually beneficial relationship between a host organism and an internal associate organism. The term is derived from the prefix "endo," meaning within, and the word symbiosis, which refers to a mutually beneficial relationship between two closely associated organisms. Another term for symbiosis is mutualism, which highlights the fact that both organisms are benefiting from the relationship.

Examples of Endosymbiosis

A well-known example of endosymbiosis is the relationship between a termite and the microorganisms in its gut. The termite consumes wood, but it cannot digest it without the help of protozoans in the termite's gut that break down the cellulose to a form that the termite can metabolize. Thus, the termite supplies food for the protozoan, and the protozoan provides food for the termite. In this example, the protozoan is the endosymbiont, or the internal organism in the endosymbiotic relationship.

There are a variety of levels...