Commensalism: This is the interaction in which one species benefits and
the other is neither harmed nor benefitted. An orchid growing as an
epiphyte on a mango branch, and barnacles growing on the back of a whale
benefit while neither the mango tree nor the whale derives any apparent
benefit.
Mutualism: This interaction confers benefits on both the
interacting species. Lichens represent an intimate mutualistic
relationship between a fungus and photosynthesising algae or
cyanobacteria. Similarly, the mycorrhizae are associations between fungi
and the roots of higher plants. The fungi help the plant in the
absorption of essential nutrients from the soil while the plant in turn
provides the fungi with energy-yielding carbohydrates.