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The complete guide to the toefl test part 7

The Complete Guide to the TOEFL® Test, iBT Edition is the most complete, accurate, and up-to-date preparation book available. It is based on years of experi-ence teaching preparation classes in the United States and abroad. It is simply written and clearly organized and is suitable for any intermediate to advanced English language student. | Reading Preview Test 19 are familiar with accidentals which are birds that appear in places far from their native areas. Sometimes they may find a habitat with favorable conditions and colonize it. Gardeners are familiar with volunteers cultivated plants that grow in their gardens although they never planted the seeds for these plants. Besides birds and plants insects fish and mammals also colonize new areas. Sweepstakes routes are unlike either corridors or filter routes in that organisms that travel these routes would not be able to spend their entire lives in the habitats that they pass through. Some organisms cross barriers with the intentional or unintentional help of humans a process called invasion. An example is the New Zealand mud snail which was accidentally brought to North America when trout from New Zealand were imported to a fish hatchery in the United States. It has caused extensive environmental damage in streams and rivers. In the invasive species native environments there are typically predators parasites and competitors that keep their numbers down but in their new habitat natural checks are left behind giving the invaders an advantage over native species. Invasive species may spread so quickly that they threaten commercial agricultural or recreational activities. Glossary salamander a type of amphibian animal resembling a lizard sweepstakes a game of chance a lottery 1 of 26 The word cosmopolitan in the passage is closest in meaning to O worldwide O useful O well-known O ancient 2 of 26 How does the author explain the concept of biological barriers in paragraph 1 O By providing several examples of biological barriers O By describing the process by which barriers are formed O By comparing biological barriers with a familiar man-made barrier O By explaining how houseflies have been affected by biological barriers 3 of 26 What does the author suggest about American bison in paragraph 2 O They spread to North America from South America. O A body of