What is the term for long-term interactions between two organisms?

The term for long-term interactions between two organisms is symbiosis. Symbiosis encompasses a range of interactions where different species live together for a prolonged period of time. This can include various types of relationships such as mutualism, commensalism, and parasitism, each of which describes specific ways in which the organisms may benefit or impact each other.

In the context of this question, symbiosis is the most comprehensive term because it refers to the overall phenomenon of long-term associations, regardless of whether those relationships are beneficial, neutral, or harmful to either organism involved. Therefore, understanding the concept of symbiosis is crucial when studying ecological relationships and interactions within ecosystems.

Mutualism, while it is a type of symbiotic relationship where both organisms benefit, is just one specific example and does not encompass the entirety of long-term interactions. Commensalism refers to a relationship where one organism benefits while the other is neither helped nor harmed, and competition involves two organisms vying for the same resources, which is not a cooperative interaction. Thus, symbiosis is the term that best captures the essence of long-term interactions between organisms.