TOEFL Sample essay : integrated essay from TPO 10

In this set of material both the passage and the speaker are talking about two theories that cause the decline of the sea otter. The reading states that, the pollution hypothesis seemed the more likely of the two. Conversely the lecture casts a shadow of doubt on what has been presented on the passage and presents some evidence to refute them.

First, the reading claims that, industrial chemical pollution that could decrease the otters' resistance to life threatening infections and thus could cause their death. But the professor says that, this theory is weakened by that, no one can find any dead of sea otter along the Alaskan coast. And if the infection will threatened sea otter it will affect the predator as well.

Second, the reading argues that, the environmental pollution affects the entire ecosystem rather than a single species. this causes other sea mammals along the Alaskan coast to decline, and not because the orcas animals because those prefer to hunt large prey such as whale. However, the professor says that, if the orcas depend on the whales in his diet, so what's happen if the whales disappear because of the human activity? So the orcas must change their diet by hunting small animals such as seals and sea lions. indeed, this is the cause that lead to decline the small animals populations.

Third , the reading claims that, the environmental factors may have created uneven concentrations of pollutants along the coast, and this could explain the uneven pattern of otter decline. But the professor says that, uneven pattern is better explained by orca predation theory than pollution theory. Orcas' availability in the location depends on if the location is accessible to orcas or not. In addition, the orca is so large and they cannot access the shallow or rocky locations in which see otter had not declined there.