What defines commensalism among organisms?

Commensalism is a type of symbiotic relationship where one organism benefits from the interaction while the other organism is neither helped nor harmed by it. This distinction is key to understanding commensalism; the benefiting organism gains some advantage—such as food, shelter, or transportation—without causing any detriment to the other involved organism.

A classic example of commensalism is barnacles attaching themselves to whales. The barnacles benefit by having a mobile platform that provides them access to nutrient-rich waters, while the whale is not significantly affected by their presence. Thus, in commensalism, the interaction underscores a balance where one organism thrives while the other remains neutral. This understanding clarifies why the correct answer reflects the characteristics of this specific symbiotic relationship distinct from other forms such as mutualism or parasitism.