第51~65题，每题1分，共15分 1、 A Special Clock Every living thing has whatscientists call a biological clock that controls behavior. The biologicalclock________(51) plants when to form flowers and when the flowers should open.It tells insects when to __________(52) the protective cocoon (防护卵袋) and fly away, and it tells animals and human beings when toeat, sleep and wake.Eventsoutside the plant and animal__________(53) the actions of some biologicalclocks . Scientists recently found, for example, that a tiny animal changes thecolor of its fur because of the __________(54) of hours of daylight. In theshort_________(55) of winter, its fur becomes white. The fur becomes gray brownin _________(56) in the longer hours of daylight in summer.Innersignals control other _________(57) clocks. German scientists found that somekind of internal clock seems to order birds to begin their longmigration_________(58) twice each year. Birds _________(59) from flying becomerestless when it is time for the trip, _________(60) they become calm againwhen the time of the flight has ended.Scientistssay they are beginning to learn which _________(61) of the brain containbiological clocks. An American researcher, Martin Moorhead, said a small groupof cells near the front of the brain__________(62) to control the timing ofsome of our actions. These __________(63) tell a person when to wake, when to_________(64) and when to seek food. Scientists say there probably are otherbiological clock cells that __________(65) other body activities.
