What type of interaction is characterized by a close and long-term biological relationship between two different species?

The interaction characterized by a close and long-term biological relationship between two different species is known as symbiosis. This term encompasses various types of relationships, including mutualism, commensalism, and parasitism, where at least one of the species benefits from the interaction. In a symbiotic relationship, the species involved often evolve together, leading to dependence for survival, resource acquisition, or other benefits.

Symbiosis highlights the importance of how different species can co-exist and influence one another, shaping ecosystems and contributing to biodiversity. For example, in a mutualistic symbiotic relationship, both species involved benefit, such as bees pollinating flowers while obtaining nectar for themselves. Conversely, in a parasitic relationship, one species benefits at the expense of the other, which does not characterize symbiosis as a mutual exchange.

Commensalism is another form of symbiosis but specifically involves one organism benefiting while the other is neither helped nor harmed, which doesn't fully encapsulate the broader definition of symbiotic relationships. Competition, on the other hand, involves two species vying for the same resources without a close biological relationship, setting it apart from the concept of symbiosis.