▶ Your Answer : As for the assertion in the reading passage, the lecturer claims that there are ways to control the zebra mussel, and it does not cause serious threat. This casts doubt on the reading passage's statement that the invasion of it cannot be stopped, and it can be led to serious threat. To begin with, according to the lecture, ships take the fresh watter as the ballast water and empties it, which can be result in flouring of the zebra mussl. However, the ships are not required to empty out the ballast water. Instead, people can refill with sea water to make the zebra mussel die. This strongly rebuts the reading passage's suggestion that the invasion made by human transportation cis unstoppable. The second point of difference in regarding its new habitat. The lecturer argues that the zebra mussels can dominate its new habitat only in the beginning. To be specific, other fishies can find new food sources, and switch from their old food. Furthermore, actually, some bird species eat the zebra mussel. Finally, the lecturer asserts that it can have positive effect on other fishes. Specifically, the zebra mussel produces nutrients for some fishes which find food sources in the botton of the lake. As a result, it can increase the population of bottom feeding fish, whereas it decreases that of plankton eating fishes. In oppose to this arguement, the reading passage contends that zebra mussels are likely to cause a decline in the overall fish population. |