写作:重复2015-11-14真题
阅读主要观点:
北美西海岸的海星得了一种消耗病(wasting disease), 针对海星得病的原因,研究人员有几种不同的猜测。
第一种猜测是寄生虫使海星生病。寄生虫依附在海星身上,并且可以在水中快速传播。所以寄生虫与海星大规模的死亡有关联。
第二种猜测是细菌使海星生病。海星吃的贝类中含有大量有害细菌。研究人员做了一个实验来验证这个猜测。将海星放置到一个容器中,并在容器中放置附近海域的贝类来喂食海星。最终,容器中的海星都生病了。
第三者猜测是水温的变化使海星生病。近年来,全球大部分水域的温度上升了,水温的上升会降低海星的免疫系统。
听力主要观点:
阅读中每个猜测都有缺陷,海星究竟为什么会得消耗病仍是个谜。
首先,海星只会在繁殖的时候被寄生虫感染,因为寄生虫是通过依附到海星的生殖器官上来传染海星。然后,海星在一年中都患有消耗病,并不只是在繁殖期患病。所以,不可能是寄生虫使海星患病。
第二,研究人员对实验中贝类携带的细菌进行仔细分析时发现,这些细菌对海星是没有危害的,海星从来没有因为这一类细菌得过病。所以,海星得病的原因仍是个谜。
第三,研究人员发现那些患有消耗病的海星所在的海域的水温并没有上升,所以不可能是水温的原因使海星生病。科学家们发现在风平浪静的海域,海星常常生病;在波涛汹涌的海域,海星反而不生病。至于为什么在风平浪静的海域海星容易生病仍然是个谜。
学生满分范文:
In the passage, the writer talks about several theories that cause sea star to get wasting disease. However, the professor thinks that each of the theories has a serious weakness and the reason is still a mysterious.
First, the author claims that the sea star wasting disease is caused by small parasites, whereas the professor argues that there is time contradict between the parasites and wasting disease. Small parasites only appear in reproduction seasons because they attach to the sea star reproductive organs. But sea star wasting disease spreads whole year round. So it is impossible for parasite causing the disease.
Second, according to the professor, the theory about bacterial carried by shellfish has some problems. The researchers analyze the shellfish in the experiment and find that the bacteria carried by the shellfish is harmless to sea stars. What’s more, this kind of bacterial never make the sea star sick before. So the reason of the wasting disease may be caused by some unknown factor.
Finally, the professor refutes that the rising temperature makes sea stars get wasting disease. Scientists find that the wasting disease occurs in the area where water temperature has remained constant and has not risen at all. Furthermore, they find that the disease occurs in the calm water area and the sea stars often get sick in the strong waves areas.