What type of species interaction occurs when one species benefits while the other is unaffected?

Commensalism is the type of species interaction where one species benefits and the other is neither helped nor harmed. This relationship allows one organism to gain resources or benefits without impacting the other species involved.

For example, certain barnacles attach themselves to the shells of turtles or the bodies of whales. The barnacles benefit from being moved to different feeding areas as the host moves about, while the turtle or whale is not affected by their presence. This illustrates how commensalism works, as the barnacles derive nourishment from the water that flows over the host without harming it in any way.

In contrast, mutualism involves both species benefiting from the interaction, parasitism involves one species benefiting at the expense of the other, and predation indicates one species (the predator) benefiting by consuming another (the prey). Each of these relationships differs fundamentally from commensalism, which is characterized specifically by the lack of impact on one of the involved species.