Which term describes a close relationship between two species that benefits at least one of them?

The term that describes a close relationship between two species that benefits at least one of them is symbiosis. Symbiosis encompasses various types of relationships between organisms, which can include mutualism, commensalism, and parasitism.

In this context, symbiosis is the overarching concept that refers to the interactions that occur when species live closely together. Mutualism is a specific type of symbiotic relationship where both species benefit, while commensalism refers to a relationship where one species benefits and the other is neither helped nor harmed. Competition, on the other hand, describes a relationship where two species vie for the same resources, which does not typically result in benefits for either organism involved.

Therefore, identifying symbiosis as the correct term provides a broad understanding of the nature of interactions between species, highlighting that at least one party benefits in the relationship.