Mutualism
In Biology, Mutualism is a interaction between species in which both organisms in a close relationship derive some degree of benefit. Mutualism can involve brief or long-term interactions (pollination versus lichen symbiosis between fungus and alga) and may or may not be obligatory for one or both partners. For example, rhizobium bacteria can reproduce either in the soil or in (usually) mutualistic symbiosis with legume plants. Mycorrhizal fungi, on the other hand, can be totally dependent on their plant hosts.See also: Parasitism, Symbiosis, Rusticle
Mutualism is the form of Anarchism described by Pierre-Joseph Proudhon.