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Species that belong to an area are said to be native species. Typically, they have been part of a given biological landscape for a long period, and they are well adapted to the local environment and to the presence of other native species in the same general habitat. Exotic species are interlopers, foreign elements introduced intentionally or accidentally into new settings through human activities. In one context an introduced species may cause no obvious problems and may, over time, be regarded as being just as "natural" as any native species in the same habitat. In another context, exotics may seriously disrupt delicate ecological balances and create a cascade of unintended consequences. The worst of these unintended consequences arise when introduced species put native species in destruction by preying on them, altering their habitats, or out-competing them in the struggle for food resources. Although biological introductions have affected environments the world over, the most destructive, effects have occurred on islands, where introduced insects, cats, pigs, rats, mongooses, and other nonnative species have caused the grave endangerment or outright extinction of literally hundreds of species during the past 500 years. One of other reason to cause species extinction is overexploitation. This word refers to the utilization of a species at a rate that is likely to cause its extreme endangerment or outright extinction. Among many examples of severe overexploitation, the case of the great whales stands out in special relief. By the middle of the 20th century, unrestricted whaling had brought many species of whales to incredibly low population sizes. In response to public pressure, in 1982 a number of nations, including the USA, agreed to an international moratorium on whaling. As a direct result, some whale species which are thought to have been on extinction's doorstep 25 years ago have made amazing comebacks, such as grey whales in the western Pacific. Others remain at great risk. Many other species, however, continue to suffer high rates of exploitation because of the trade in animal parts. Currently, the demand for animal parts is centered in several parts of Asia where there is a strong market for traditional medicines made from items like tiger bone and rhino horn.
Read the following passage and mark the letter A. B. C or D your answer sheet to indicate the correct answer to each of the questions.
CAN ANIMALS TALK?
In 1977, a young Harvard graduate named Irene Pepperberg brought a one-year-old African gray parrot into her lab, and attempted something very unusual. At a time when her fellow scientists thought that animals could only communicate on a very basic level, Irene set out to discover what was on a creature's mind by talking to it. The bird, named Alex, proved to be a very good pupil.
Scientists at the time believed that animals were incapable of any thought. They believed that animals only reacted to things because they were programmed by nature to react that way, not because they had the ability to think or feel. Any pet owner would probably disagree. Pepperberg disagreed, too, and started her work with Alex to prove them wrong.
Pepperberg bought Alex in a pet store. She let the store's assistant pick him out because she didn't want other scientists saying later that she'd deliberately chosen an especially smart bird for her work. Most researchers thought that Pepperberg's attempt to communicate with Alex would end in failure.
However, Pepperberg's experiment did not fail. In fact, over the next few years, Alex learned to imitate almost one hundred and fifty English words, and was even able to reason and use those words on a basic level to communicate. For example, when Alex was shown an object and was asked about its shape, color, or material, he could label it correctly. He could understand that a key was a key no matter what its size or color, and could figure out how the key was different from others.
Pepperberg was careful not to exaggerate Alex's success and abilities. She did not claim that Alex could actually “use” language. Instead, she said that Alex had learned to use a two-way communication code. Alex seemed to understand the turn-taking pattern of communication.