In which type of relationship does one animal benefit while the other is harmed?

The type of relationship in which one animal benefits while the other is harmed is known as parasitism. In this interaction, the parasite derives some benefits, such as nourishment or shelter, from its host, which is negatively affected by the presence of the parasite. The host may experience a range of detrimental effects, including illness, reduced fitness, or even death depending on the severity of the parasitic relationship.

This concept is crucial in understanding ecological interactions and the balance of ecosystems, as parasitism can regulate host populations and impact community dynamics. The other options describe different types of interactions: mutualism is beneficial to both organisms, commensalism benefits one while the other is unaffected, and symbiosis encompasses various interactions including both positive and negative relationships but does not specifically denote the harmful aspect to one party as seen in parasitism.