TPO 10

The lecture states that environmental pollution is the main reason that declined the population of small mammals (the sea otter) and provides three reasons. The professor, however, specifies that investigations about the problem show that the predation theory is more accurate and refutes them all.

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

Second, the article explains that other sea mammals such as seals and sea lions' population has been declined on the coast and affects the entire ecosystem. Also, the orca one of the predators prefers to hunt much larger 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 has been hunted by humans. Therefore, the orca is the main reason that the mammal population is declined.

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