SYMBIOSIS
A relationship in which two species live together closely is called symbiosis. The type of symbiosis in which one species gets benefit while the other species is neither benefited nor harmed is called commensalism. For example lichens and small plants grow on the trunk of big trees. They get nutrients from tree while the tree gets no barm or benefit. A symbiotic relationship in which both species get benefit is called mutualism. An example is the relationship between flowers and the insect that pollinate them. The flower provides food to the insect in the form of nectar. In returns, the insect help in the cross pollination of flower.
Commensalism, Mutualism and Parasitism.
Source
