托福口语 Task 3

In biology, the concept of 'commensalism' describes a relationship between two species where one benefits and the other is neither helped nor harmed. The benefiting species often gains food, shelter, or transport, while the host species remains unaffected. This interaction is distinct from mutualism, where both species benefit, and parasitism, where one species harms the other. Commensalism is common in nature, such as when smaller organisms attach to larger animals for movement without impacting the host's survival.

Professor: So, let me give you a clear example of commensalism from a recent study. Researchers observed barnacles attaching themselves to the skin of humpback whales. The barnacles get a free ride across oceans, which allows them to reach new feeding areas and filter plankton from the water. They also gain protection from predators because the whale's size deters most threats. Now, what about the whale? The scientists tracked several whales over months and found no signs of injury, increased energy expenditure, or reduced feeding efficiency due to the barnacles. The whales continued their normal migration and feeding patterns. So, the barnacles clearly benefit—they get transportation and food access—but the whale seems completely unaffected. This perfectly illustrates commensalism.