Commensalism is best defined as?

• A. Both species harmed
• B. One benefits, the other harmed
• C. One benefits, the other unaffected
• D. Both benefit

Answer: (C)

In commensalism, one species gains a benefit while the other is largely unaffected. An example is a remora hitching a ride on a shark to access scraps and transportation, with the shark not gaining or losing significantly from the association. This stands in contrast to parasitism, where the host is harmed, and mutualism, where both partners benefit. Another marine example is barnacles attached to a whale, where the barnacle benefits from access to water flow and food particles and the whale is mostly unaffected.