Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What type of ecological interaction occurs between remora fish and whales?

1. Mutualism

2. Commensalism

3. Parasitism

4. Predation

The correct answer is: Commensalism

The interaction between remora fish and whales exemplifies commensalism, where one organism benefits while the other is neither helped nor harmed. In this relationship, remora fish attach themselves to whales using a special sucker on their heads. By hitching a ride on the whale, remoras gain access to food scraps that the whale leaves behind while feeding, which provides them with nutrition. The whale, on the other hand, does not benefit from the remora being there, nor is it negatively impacted by the presence of the fish. This lack of effect on the whale characterizes the commensalism dynamic. In contrast, mutualism would involve both parties benefiting, which is not the case here; parasitism would imply that one organism benefits at the expense of the other, leading to harm, and predation involves one organism eating another, which doesn't apply to the remora-whale relationship.