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  3. In matters biological, whether large or small, it is a good bet that what Charles Darwin said back in the 19th century is correc

In matters biological, whether large or small, it is a good bet that what Charles Darwin said back in the 19th century is correc

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问题     In matters biological, whether large or small, it is a good bet that what Charles Darwin said back in the 19th century is correct. One idea he had, which has not hitherto been put to the test, is that waterborne invertebrates frequently spread by hitching lifts on birds. On this, it turns out, he was right as well.
    Darwin noticed that when he suspended a duck’s foot in an aquarium, invertebrate larvae attached themselves to it and held on tight for many hours, even if he removed it from the water. Sadly, he died before he could explore this phenomenon in the wild. But Joseph Simonis and Julie Ellis just have.
    Dr. Simonis, who works at Lincoln Park Zoo in Chicago, and Dr. Ellis, of Tufts University in Massachusetts, put Darwin’s idea to the test on Appledore Island in Maine, where thousands of rain-filled rock pools sit. These pools host such animals as water fleas, rotifers and seed shrimps. Since these creatures are incapable of cross dry land by themselves, the two researchers thought they might be making use of birds to hop between pools, as Darwin suggested.
    Dr. Simonis and Dr. Ellis therefore collected 25 young gulls that had been dabbling in the pools(juveniles are easier to catch because they cannot yet fly)and 25 others that they had followed for at least 20 minutes, and had not seen go into a pool in that time. They gave every bird a bath in a tub of water for five minutes and sieved the water afterwards to see what had floated off.
    They report in Ecology that 16 of the gulls which had been dabbling carried larvae or viable eggs when they were given their enforced bath. One, indeed, had 18 such creatures attached to it. Of those gulls that had been away from the water, only two carried hitchhiking invertebrates. Gulls, then, certainly are picking up passengers when they bathe. But are they dropping them at suitable destinations?
    The answer to that seems to be "yes" , too. Pools in areas with lots of gulls shared 80% of their species. That dropped to 50% in places where the birds were few and far between. It therefore looks as though gulls are homogenising the local ecosystems by carrying invertebrates around. Chalk another one up to Charles.
Water fleas, rotifers and seed shrimps are ______.
选项 A、food of the birds
B、enemies of the birds
C、different kinds of fish
D、waterborne invertebrates
答案D
解析 根据题干的water fleas，rotifers and seed shrimps定位到第三段第二句，下一句以these creatures来指代这些生物，而接下来两个段落也在描写有关这些生物的实验，第五段第二句指出：One，indeed，had 18 such creatures attached to it．故可以得知such creatures=these creatures=water fleas…而第五段第三句明确指出：Of those…only two carried hitchhik—ing invertebrates．由此可见such creatures=hitchhiking invertebrates，故[D]为本题答案。
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