托福 tpo26 综合写作范文

In terms whether the zebra mussel will exert negative influence on North American, the passage and lecture are contradictory to each other. The author believes that zebra mussel might do harm the local species as they arrived while the lecturer holds a different opinion.

First of all, the author makes a point that the history events suggest the zebra mussel's invasion is unstoppable. In the past, human transportation makes it possible for zebra mussel spread around the whole Europe and it is likely to happen again in North American. However, the lecturer demonstrates a different idea that a change made in the "ballast water" will prevent the invasion of zebra mussel from continuing. He says that if we refill the "ballast water" with ocean water, the mussel will no longer survive because the saline water might probably kill them all.

Second, contrary to the belief in the passage that zebra mussel is able to conquer the new habitat due to their high reproduction rates and adaptation ability, as well as lacking predator, the lecturer says that the hypothesis made by author is not true. He mentions that there are many local bird will eat the zebra mussel as a major prey. As a result, the zebra mussel is unlikely to dominate the new habitat.

Finally, regarding whether the zebra mussel will cause the decline in the fish population since they may compete for food such as plankton with fish species. The author thinks it is a possible consequence brought by zebra mussel. However, the lecturer refutes it that the mussel can't reduce the fish population because they provide enough nutrient for bottom living fish.