are living creatures which works with another creature, and depends on that creature for its life.

are species living with a cooperating host species in a relationship that is mutually beneficial. References Campbell, R.D. 1987. A new species of Hydra (Cnidaria: Hydrozoa) from North America with comments on species clusters within the genus. Zoological Journal of the Linnean Society 91. Lenhoff, H.M., 1983. Hydra: Research Methods. Plenum Press, New York. Thorp, J.T. and Kovich, A.P. 1991. Ecology and Classification of North American Freshwater Invertebrates. Academic Press, San Diego.

organisms of two different species that exist in a close interrelationship that is benfical to both.

Two dissimilar organisms that each benefit from the presence of the other, for example, rhizobium and the members of the Fabaceae (Leguminosae).

An organism which lives together in more or less intimate association with another, dissimilar organism in a mutually beneficial relationship. An organism which maintained a similar, but non-beneficial relationship would be called a parasite.

Usually refers to at least two organisms that need each other to survive, with one organism living within the other organism.

organisms that live together to mutual benefit [e.g., nitrogen-fixing bacteria that live with a plant (legume)

Organisms that are living in a mutually beneficial association with organisms from another species.

species that live together closely