In this set of materials, the eriter and the lecturer discus the issue of zebra mussels' growing expansion. the reading passage claims that there is no way to control the increasing number of zebra mussels. However, the lecturer brings up several points that contradict this argument.
First of all, the lecturer contends that by using salt water, the population growth of zebra mussels can be stopped. This casts doubt on the writer's assertion that the expansion of zebra mussels trransported in the ballas water has been increased quickly because there is no way to slow down their firtilizion.
Another point the lecturer makes is that as birds are zebra mussels' natural predator, by letting them live around those mussles, they can stop the expansion of its population. He adds that when there is no longer preies left, bird will start to eat them. This point effectively counters the writer's argument that due to no predator existing and easily surviving, they turn out predominet once they are introduced into any water.
Lastly, according to the lecturer, advantages of zebra mussels far outweight disadvantages of them. He states that not only they make bottom dwelling fish more productive but also they make water clean which resuts in offering better habitats. This directly refutes the reading passage's point that as they compete for plankton, they disconstruct the chain.
19분