TPO10

The lecture states that the enviromental pollution is the main reason that declined the population of small mammal (the sea otter) and provides three reasons. The professor, however, specifies that investigations about the problem shows that the predation theory are more accurate and refute them all.

First, based on the reading, water samples from the western coast shows that the chemical levels is highten and because of that the otters' resistance is declined. In contrast, the lecturer asserts that, the pollution are not the main reasons since the dead body of otters are not find in waters. Since water could not wash up the body of others, the predators theory are more plausible.

Second, the article explains that other sea mammals such as seals and sea lions population has been declined in the coast and affects the entire ecosystem. Also, the orca one of predator prefer to hunt muchlarger prey, therefore, the predator assumption is wrong. On the contrary, according to the professor, the orca has changed its diet because its source of feed have been hunted by humans. Therefore, the orca are the main reason than the mamals population is declined.

Third, the reading states that only the environmental pollution explains the uneven pattern of otter decline. Nevertheless, the speaker says that the predators theory better explain this pattern. Because the predators have larger body size and could not reach shallow places that the sea other live. Hence, places that are not accessable for whales, have more popullation.