在托福寫作練習過程中，相信TPO材料中的作文題目都會是大家的首選練習材料。上海新航道托福小編給考生們帶來了托福綜合寫作TPO10，希望可以幫助廣大托福考生輕松備考托福。

  TPO10

  Reading

  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 caused much concern because sea otters play an important ecologicalrole 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 seemed the more likely of the two.

  The first reason why pollution seemed the more likely cause was that there were known sources of it along the Alaskan coast, such as oil rigs 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.

  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 environmental pollution, since it usually affects 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.

  Third, scientists believed that the pollution hypothesis could also explain the uneven pattern of otter decline: at some Alaskan locations the otter populations 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.

  Listening

  Professor:

  Well, ongoing investigations have revealed that predation is the most likely cause of sea otter decline after all. Well, ongoing investigations have revealed that predation is the most likely cause of sea otter decline after all.

  First, the pollution theory is weakened by the fact that no one can really find any dead sea others washing off on Alaskan beaches. That's not what you would expect if infections caused by pollution started killing a lot of otters. On the other hand, the fact that it's so hard to find dead otters is consistent with the predator hypothesis. If an otter is killed by a predator, it's eaten immediately so it can't wash up on shore.

  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 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.

  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 sea otters has declined greatly. However, because orcas are so large, they can't access shallow or rocky locations. And shallow and rocky locations are precisely the types of locations where sea otter populations have not declined.

  以上就是小編為大家?guī)黻P(guān)于托福TPO閱讀資料供大家閱讀參考，新航道托福資料頻道將第一時間為考生發(fā)布最全、最新、最專業(yè)的托福資訊及托福考試資料及機經(jīng).