TPO26

Both the reading passage and the professor's lecture discuss the zebra mussel. The reading passage implies that the intrusion of zebra mussel is unstoppable and it threatens the freshwater fish population that dwell in North America. However, the professor strongly disagrees with the reading passage. According, he presents three refutations.

First of all, the reading passage mentions that invasion cannot be stopped. Yet, the lecturer severely challenges the theory by arguing that people have limited knowledge. Furthermore, he states that there are ways to prevent ship spreading this creature to new locations by replacing the ballast water to ocean water. Consequently, salt water kills zebra mussel and it cannot spread out. Therefore, the invasion of zebra mussels can be successfully avoided actually.

Secondly, the reading suggests that as long as zebra mussels arrives a new habitat, they will be able to dominate the new environment. Nevertheless, the scholar contradicts the hypothesis by asserting that domination is only in beginning. Moreover, the predators of zebra mussel finally may switch the major food from other creatures to zebra mussels. Also, the professor proposes that the predators eat a lot of zebra mussels. As a result, it is unlikely for mussels to dominate their habitats.

Last but not least, the reading article indicates that zebra mussels may bring about declination of population of fish in habitats. Once again, the speaker opposes the evidence revealed in the article by assuming that zebra mussels not only destroy the certain species that eat plankton, but also benefit others that get nutrient from mussels. Apparently, the third explanation is also unconvincing.