It is a type of interaction between two organisms where both the interacting species are benefited mutually. It is also known as symbiosis.

Examples of Mutualism

(i) Mycorrhiza living in roots of higher plants: in this interaction the root provides food and shelter to the fungus and the fungus help in absorption of minerals, water uptake and also provide protection against pathogenic fungi.

(ii) Rhizobium in root nodules of legumes: plant root provide food and shelter to the bacteria and the bacteria help is fixing of nitrogen and absorption of nitrogen

(iii) Algae and fungi in lichens: the fungus provide water, mineral and shelter to the algae. Algae manufacture food not only for itself but also for the fungi.

(iv) Orchid Orphreys and bee for pollination: orchid is pollinated by the plant and in return they get rewards in the form of nectar.