TOEFL integrated writing: The sea otter

Sea otters are small sea mammals living along the western coast of North America. The passage states that in recent years the number of this animals declined in this area. Seemingly, passage believes environmental pollution is cause and provides three reasons. However, the professor explains that investigations proof pollution is not the reason and predation theory is logical and refutes all of author reasons.

First, the reading states that oil rigs and industries chemical pollution is the reason. On the other hand, the professor states if the pollution was reason they should found corps on the beach. However, any dead body of otters not founded. Thus the reason cannot be sea pollution.

Second, article claims that coincidentally with otters other sea mammals are disappeared. Author believes it cannot happen by Orcas because they hunt big animals like walls. However, the lecturer contends that it could have done by Orcas and mentions due to lack of walls, which was disappeared by humans, Orcas have changed their diet ant hunt small mammals like seals and sea lions.

Third, the reading avers that pollution can be the cause because this event happened just in some places and these places can be the dense of pollution. The lecturer opposes this point by saying that this is the evidence for Orca's theory because some exception places which are not attacked by Orcas are some rocky and shallow locations. She says because Orcas are big they cannot access to such places and for this reason in these locations the number of otters have not declined.
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