TOEFL Speaking Task 3

In biology, the concept of 'commensalism' refers to a symbiotic relationship between two species in which one species benefits while the other is neither helped nor harmed. The benefiting species often gains food, shelter, or transportation, while the host species remains unaffected in its survival or reproduction. Commensalism is one of three main types of symbiosis, alongside mutualism, where both species benefit, and parasitism, where one benefits at the expense of the other. This relationship is common in nature, though it can be subtle and sometimes difficult to observe without careful study.

Professor: Let me give you a classic example of commensalism. Consider the remora, also known as the suckerfish. Remoras have a specialized suction cup on top of their heads. They attach themselves to larger marine animals, like sharks or manta rays. When the shark feeds and scraps of food fall away, the remora quickly detaches to eat those leftovers. The remora clearly benefits because it gets an easy meal without expending energy to hunt. Now, what about the shark? Does it suffer? Not really. The shark doesn't lose food that it would have eaten anyway—these scraps are just waste. The shark also doesn't seem to be harmed by the remora's presence. In fact, the remora is so small and light that it doesn't slow the shark down or cause physical damage. The shark simply goes about its day, completely unaffected. So, the shark is neither helped nor hurt. This perfectly illustrates commensalism: one species gains a benefit, the other is neutral.