In which scenario do two organisms live close together and at least one benefits?

The situation where two organisms live in close proximity and at least one benefits from the relationship is referred to as symbiosis. This term encompasses various types of interactions between species, including mutualism (where both species benefit), commensalism (where one species benefits while the other is neither helped nor harmed), and parasitism (where one benefits at the expense of the other). However, the common characteristic that defines symbiosis is the close living arrangement and the potential for at least one organism to benefit.

In contrast, competition involves two organisms vying for the same resources, which typically does not lead to any benefits for either party involved. Predation describes a relationship where one organism (the predator) feeds on another organism (the prey), which does not align with the idea of both organisms living closely together with at least one benefiting. Parasitism, while it does involve one organism benefiting at the cost of another, is a more specific type of symbiotic relationship where the parasite usually harms the host. Thus, symbiosis is the broadest term that accurately captures the scenario described in the question.