The term for a symbiotic relationship in which both species benefit is mutualism. In a mutualistic interaction, each participant gains a net advantage, such as food, protection, nutrients, or help with reproduction.
One classic example is the partnership between flowering plants and pollinators. The plant receives pollen transfer between flowers, while the insect, bird, or other pollinator obtains nectar or pollen as food. Another important example involves plant roots and mycorrhizal fungi: plants provide carbohydrates, while fungi improve the plant’s access to minerals such as phosphate.
The word mutualism was introduced by Belgian zoologist Pierre-Joseph van Beneden in 1876. Mutualism can be obligate, meaning one or both species depend on the relationship, or facultative, meaning both can survive without it.
Mutualism is often confused with symbiosis. Symbiosis describes a close, long-term relationship and includes mutualism, parasitism, and commensalism. In parasitism, one species benefits while the other is harmed; in commensalism, one benefits and the other is largely unaffected.