托福寫作TPO10綜合寫作詳細解析

1、精選優(yōu)質文檔-傾情為你奉上智課網(wǎng)TOEFL備考資料托福寫作TPO10綜合寫作詳細解析 阿拉斯加州的海獺數(shù)量在減少?是環(huán)境污染?還是天敵捕食? 閱讀材料： The sea otter is a small mammal that lives in waters along the western coast of North America from California to Alaska. When some sea otter populations off the Alaskan coast started rapidly declining a few years ago, it ca

2、used much concern because sea otters play an important ecological role in the coastal ecosystem. Experts started investigating the cause of the decline and quickly realized that there were two possible explanations: environmental pollution or attacks by predators. Initially, the pollution hypothesis

3、 seemed the more likely of the two. 海獺是一種生活在北美西海岸從加州到阿拉斯加沿線的小型海洋哺乳動物。幾年前，阿拉斯加海岸的海獺數(shù)量急劇減少。由于海獺對于維持海岸沿線生態(tài)平衡有非常重要的作用，所以其數(shù)量下降引起了廣泛的關注。專家開始研究海獺數(shù)量下降的原因，并且很快發(fā)現(xiàn)了兩個可能的原因，分別是環(huán)境污染和天敵捕食。最初，環(huán)境污染說看起來更為可信。 The first reason why pollution seemed the more likely cause was that there were known sources of it along the

4、 Alaskan coast, such as oil rings and other sources of industrial chemical pollution. Water samples from the area revealed increased levels of chemicals that could decrease the otters resistance to life-threatening infections and thus could indirectly cause their deaths. 為什么污染說更為可信呢?這是因為阿拉斯加海岸確實有污染源

5、，比如石油帶或者其他的工業(yè)污染物。該地的水樣顯示水中化學物的含量增加，其數(shù)量可以導致海獺對于對于一些致命感染喪失抵抗力，進而間接導致數(shù)量下降。 Second, other sea mammals such as seals and sea lions along the Alaskan coast were also declining; indicating that whatever had endangered the otters was affecting other sea mammals as well. This fact again pointed to environmen

6、tal pollution, since it usually affect the entire ecosystem rather than a single species. Only widely occurring predators, such as the orca (a large predatory whale), could have the same effect, but orcas prefer to hunt much larger prey, such as other whales. 第二，在阿拉斯加海域，包括海豹和海獅在內的其他海洋哺乳動物的數(shù)量也有所下降。這表

7、明造成海獺數(shù)量下降的原因也對其他海洋哺乳動物造成了影響。原因再次指向了環(huán)境污染，這是因為環(huán)境污染問題常常不是僅僅影響某個特定物種，而是影響整個生態(tài)系統(tǒng)。除此之外，只有像逆戟鯨(一種大型肉食鯨)那種食性廣泛的動物才能通過捕食呈現(xiàn)相同的效果。但是，逆戟鯨更喜歡捕食像鯨類這種的大型獵物。 Third, scientists believed that the pollution hypothesis could also explain the uneven pattern of otter decline: at some Alaskan locations the otter populatio

8、ns declined greatly, while at others they remained stable. Some experts explained these observations by suggesting that ocean currents or other environmental factors may have created uneven concentrations of pollutants along the coast. 第三，科學家認為污染說同時可以解釋海獺數(shù)量變化的不均衡性。所謂不均衡性是指在阿拉斯加某些區(qū)域海獺數(shù)量下降明顯，而在其他地方海獺的

9、數(shù)量保持未定。一些專家指出這樣的觀察結果表明洋流和其他環(huán)境因素導致了海岸線上污染物的不均衡聚集。 閱讀部分需要提取的觀點是： - Main point: 海獺數(shù)量下降的原因是環(huán)境污染 - Sub point 1:阿拉斯加海域確有污染源 - Sub point 2:除海獺外，還有其他哺乳動物的數(shù)量下降 - Sub point 3:不同區(qū)域海獺數(shù)量下降情況不同，可以解釋為污染物聚集情況不同導致的。 聽力材料： Well, ongoing investigations have revealed that predation is the most likely cause of sea otter

10、 decline after all. 目前的研究表明天敵捕食是最可能導致海獺數(shù)量減少的原因。 First, the pollution theory is weakened by the fact that no one can really find any Dead Sea otters washing off on Alaskan beaches. Thats not what you would expect if infections caused by pollution started killing a lot of otters. On the other hand, th

11、e fact that its so hard to find dead otters is consistent with the predator hypothesis. If an otter is killed by a predator, its eaten immediately so it cant wash up on shore. 首先，由于沒有人發(fā)現(xiàn)有海獺尸體被沖上阿拉斯加海灘，所以污染理論捕食那么站得住腳的。如果污染造成的疾病感染導致了海獺數(shù)量的劇減，那么情況不該如此。而且，很少發(fā)現(xiàn)海獺尸體也恰恰說明了天敵捕食假說。捕食者殺死了海獺后，會很快地吃掉它，那么我們也就不會再岸

12、上發(fā)現(xiàn)海獺尸體了。 Second, although orcas may prefer to hunt whales, whales have essentially disappeared from the area because of human hunters. That means that orcas have had to change their diet to survive and since only smaller sea mammals are now available, orcas have probably started hunting those. So,

13、it probably is the orcas that are causing the decline of all the smaller sea mammals mentioned in the passage - the seals, the sea lions, and the sea otters. 第二，盡管逆戟鯨喜歡捕食鯨類，但是鯨類的數(shù)量卻由于人類的捕獵活動而劇烈減少。這意味著逆戟鯨不得不為了生存而更改捕食習慣。目前來看只有一些小型海洋哺乳動物還可以捕捉，逆戟鯨很可能開始以它們?yōu)槭沉?。所以，很可能是逆戟鯨的捕食導致了文中提到的諸如海豹、海獅和海獺等小型哺乳動物的數(shù)量減少。

14、And third, the uneven pattern of otter decline is better explained by the orca predation theory than by the pollution theory. What happens to otters seems to depend on whether the location where they live is accessible to orcas or not. In those locations that orcas can access easily, the number of s

15、ea otters has declined greatly. However, because orcas are so large, they cant access shallow or rocky locations. And shallow and rocky locations are precisely the types of locations where sea otter populations have not declined. 第三，海獺數(shù)量變化的不均衡性恰好表明了逆戟鯨捕食理論比污染理論更合理。海獺數(shù)量的增減取決于它們生存的地方逆戟鯨是不是可以進入。在那些逆戟鯨很容易進入的海域，海獺的數(shù)量急劇減少。然而，因為逆戟鯨個頭很大，所以他們不能進入那些過淺或者充滿巖石的海域。而那些過淺和充滿巖石的海域，恰恰是海獺數(shù)量保持穩(wěn)定的地區(qū)。 聽力筆記內容： Main point: 天敵說更為可信 Sub point one: 沒有發(fā)現(xiàn)海獺的尸體 Sub point two: