Which type of relationship benefits one organism while the other is neither helped nor harmed?

The type of relationship that benefits one organism while the other is neither helped nor harmed is known as commensalism. In this interaction, one species gains advantages, such as food, shelter, or transportation, without causing any significant impact on the other species involved.

A classic example of commensalism is the relationship between barnacles and whales. Barnacles attach themselves to the skin of whales, benefiting from the nutrient-rich water that flows over the whale as it swims. The whale, meanwhile, is generally unaffected by the presence of barnacles, illustrating the essence of commensalism as one organism benefits while the other remains neutral in its experience.

In contrast, mutualism refers to a symbiotic relationship where both organisms benefit, parasitism involves one organism benefiting at the expense of another, and synergism relates to interactions where two or more organisms enhance each other's functionality or growth, which is more collaborative rather than exploitative like parasitism. These distinctions clarify why commensalism is the correct answer in this context.