This is an essay for toefl integrated writing, I'm looking forward suggestions not about content, but about grammar and means of expression, Thank you in advance!
As can be seen in the reading passage, there are several reasons to believe the invasion of zebra mussel cannot be stopped, however, the lecturer rejects all of reasons.
First of all, the reading passage utilizes the history spread of zebra mussel to conclude that this species will soon colonize all of North America. Yet the lecturer says the unstoppable history invasion can be attribute to lack of knowledge of past people, he points out that zebra mussel spread out by ship in the ballast water, which is important for zebra mussel, and it must be fresh water. So nowadays, people can get rid of zebra mussels by substitute the fresh water with sea water in order to kill the zebra mussels, which cannot be survive in soil water.
In addition, the stand in the listening material casts doubt on the theory about dominating new habitat. The lecturer believes that zebra mussels will dominate the new habitat at beginning, but then there will be new predators, like birds, eat zebra mussels, in other words, this new predator will prevent zebra mussels from dominating.
Finally, with regard to the fish population, it is true that zebra mussels will have impact on some fish population, but not all kinds of fish. The lecturer says the process of zebra mussels eat plankton will provide enough nutrients for the bottom fish, and then lead to a increase of this kind of fish.
As can be seen in the reading passage, there are several reasons to believe the invasion of zebra mussel cannot be stopped, however, the lecturer rejects all of reasons.
First of all, the reading passage utilizes the history spread of zebra mussel to conclude that this species will soon colonize all of North America. Yet the lecturer says the unstoppable history invasion can be attribute to lack of knowledge of past people, he points out that zebra mussel spread out by ship in the ballast water, which is important for zebra mussel, and it must be fresh water. So nowadays, people can get rid of zebra mussels by substitute the fresh water with sea water in order to kill the zebra mussels, which cannot be survive in soil water.
In addition, the stand in the listening material casts doubt on the theory about dominating new habitat. The lecturer believes that zebra mussels will dominate the new habitat at beginning, but then there will be new predators, like birds, eat zebra mussels, in other words, this new predator will prevent zebra mussels from dominating.
Finally, with regard to the fish population, it is true that zebra mussels will have impact on some fish population, but not all kinds of fish. The lecturer says the process of zebra mussels eat plankton will provide enough nutrients for the bottom fish, and then lead to a increase of this kind of fish.