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  3. Every living thing has an inner biological clock that controls behavior. The clock works all the time; even when there are no ou

Every living thing has an inner biological clock that controls behavior. The clock works all the time; even when there are no ou

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问题     Every living thing has an inner biological clock that controls behavior. The clock works all the time; even when there are no outside signs to mark the passing of time. The biological clock tells plants when to form flowers and when the flowers should open. It tells insects when to leave the protective cocoon and fly away. And it tells animals when to eat, sleep and wake. It controls body temperature, the release of some hormones(荷尔蒙)and even dreams. These natural daily events are circadian(生理节奏的)rhythms.
    Man has known about them for thousands of years. But the first scientific observation of circadian rhythms was not made until 1729. In that year French astronomer, Jean-Jacques d’Ortous de Mariran, noted that one of his plants opened its leaves at the same time every morning, and closed them at the same time every night. The plant did this even when he kept it in a dark place all the time. Later scientists wondered about circadian rhythms in humans. They learned that man’s biological clock actually keeps time with a day of a little less than 25 hours instead of the 24 hours hours on a man-made clock.
    About four years ago, an American doctor, Eliot Weitzman, established a laboratory to study how our biological clock works. The people in his experiments are shut off from the outside world. They are free to listen to and live by their circadian rhythms. Dr. Weitzman hopes his research will lead to effective treatments for common sleep problems and sleep disorders caused by ageing and mental illness. In the first four years of research, Dr. Weitzman and his assistant have observed 16 men between the ages of 21 and 80. The men remained in the laboratory for as long as six months. Dava Sobol became the first woman to take part in the experiment. She entered the laboratory on June 13th and stayed for 25 days. Miss Sobol wrote reports about the experiment during that time, which was published in the newspaper.
The biological clock is believed to play an essential role in______.
选项 A、the regulation of body temperature
B、the secretion of hormones
C、animal reproductions
D、many aspects of plant and animal physiology
答案D
解析 概括题。答案在第一段。生物钟能告诉植物何时结花蕾、何时开花；能告诉昆虫何时离开虫茧、展翅飞翔；能告诉动物何时觅食、何时睡觉和起来。除此之外，生物钟还能控制体温和荷尔蒙的释放，甚至是做梦。综上所述，可知生物钟在动植物的生理方面扮演了不可或缺的角色，故D是正确答案。
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