What type of relationship is characterized by one organism benefiting while the other is harmed?

The relationship characterized by one organism benefiting while the other is harmed is known as parasitism. In this interaction, the parasite derives advantage at the expense of the host. The parasite typically relies on the host for nutrients and often inflicts some level of damage or harm to the host organism, which can affect its health, reproduction, or survival.

In contrast, the other types of relationships mentioned differ fundamentally in their interactions. Commensalism involves one organism benefiting while the other is neither helped nor harmed. Mutualism is a relationship where both organisms benefit from the interaction. Predation describes the interaction where one organism (the predator) benefits by feeding on and killing another organism (the prey), but it is a different dynamic from parasitism, as it often leads to the death of the prey as opposed to a more sustained interaction like that of parasites and hosts. Thus, parasitism is a distinct relationship focused on the harm experienced by the host organism while the parasite thrives.