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托福official75综合写作生态学类Integrated Writing范文+题目解析

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Directions: You have 20 minutes to plan and write your response. Your response will be judged on the basis of the quality of your writing and on how well your response presents the points in the lecture and their relationship to the reading passage. Typically, an effective response will be 150 to 225 words.

Summarize the points made in the lecture, being sure to explain how they challenge the specific theories presented in the reading passage.

题目原文：

The Northern Pacific sea star, which is native to the coasts of Japan, Korea, and China, has recently appeared thousands of kilometers away. Because this sea star now threatens to harm marine ecosystems in new and distant areas, scientists are currently investigating ways of controlling the spread of invasive Northern Pacific sea stars. Quicklime One method of reducing Northern Pacific sea star populations is by administering a poison called quicklime. Quicklime in its powdered form can be spread over large areas of the seafloor invaded by the sea stars. While quicklime destroys sea stars, it does not harm commercially important mollusks, such as oysters, scallops, and mussels, which are cultivated on the seafloor in many waters. Introducing Parasites A second strategy is to introduce parasites that naturally control the spread of Northern Pacific sea stars in their native habitat. One major reason why Northern Pacific sea star populations are flourishing in distant waters is the absence of natural enemies, such as parasites. In their native environment, male sea stars are infected by parasites that specifically attack their reproductive system. If these parasites became established in distant waters, invasive Northern Pacific sea star populations could be significantly decreased. Treating Ballast Water A third measure involves sterilizing ballast water. Ships that have unloaded their cargo take aboard some amount of sea water as a weight and balance stabilizer. This sea water is referred to as ballast water. Sea star larvae (immature sea stars) float freely in the sea and are often taken up in ballast pumps. After taking aboard ballast water with numerous larvae in Northern Pacific waters, ships dump this water in ports thousands of kilometers away and thus contribute to the spread of these sea stars. If ships treated their ballast water with chemicals before releasing it in a different location, Northern Pacific sea stars could be prevented from spreading to new areas.

题目音频：

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听力原文

Now listen to part of a lecture on the topic you just read about.

Unfortunately, while the measures described in the reading will help, none will really stop invasive Northern Pacific sea stars from spreading.

First, quicklime doesn't hurt commercially important mollusks, but that doesn't mean it's safe for the entire marine ecosystem. You see, this poison destroys not only invasive Northern Pacific sea stars but also native ones. And native sea stars are critical to maintaining their local ecosystems. Once quicklime is spread over the sea floor, it remains active there for a long time, and that'll be a problem for native sea stars. Soon after the quicklime kills the invasive sea stars, native sea stars will move into the sea floor areas where the invasive sea stars used to live, and when that happens, they'll die too.

Second, the idea of importing some of the Northern Pacific sea stars’ natural enemies is unlikely to work as well as the reading would have you believe. The problem with parasites is that they do not completely destroy male northern pacific sea stars’ reproductive system. This means that male sea stars infected with the parasite will still be able to fertilize the eggs of females. And given that a single female can produce up to 20 million eggs, it seems unlikely that introducing these parasites into habitats that the Northern Pacific sea star has invaded will have much impact on the population of these sea stars.

Finally, sterilizing the ballast water of ships is unlikely to prevent Northern Pacific sea star larvae from spreading to new locations. Unfortunately, ballast water isn't the only way that sea star larvae are transported from place to place. While floating in the sea, Northern Pacific sea star larvae stick to objects around them. For example, to the bottom of small boats or to equipment used for fishing. because of their ability to stick to objects around them. Invasive northern pacific sea stars will likely continue to spread to new areas regardless of whether ships sterilize their ballast water or not

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