Which relationship describes one organism benefiting at the cost of another organism?

The relationship that describes one organism benefiting at the cost of another organism is parasitism. In parasitism, one organism, the parasite, derives benefits such as nutrients and shelter from another organism, known as the host, which is harmed in the process. This harm can manifest in various ways, including the depletion of resources, disease, or overall weakening of the host.

Parasitism is a specific type of interaction that differs from other ecological relationships. For instance, mutualism involves both organisms benefiting from the interaction, whereas commensalism describes a scenario where one organism benefits while the other is neither helped nor harmed. Competition refers to the struggle between organisms for limited resources, which does not fit the description of one benefiting at the expense of another. Therefore, understanding parasitism is crucial in ecology as it highlights the complex interdependencies within ecosystems and the impact of these interactions on both individual species and the community as a whole.