Every living thing has what scientists call a biological clock that controls behaviors. The biological clock tells plants when to form flowers and when the flowers should open. It tells insects when to leave the protective cocoons and fly away, and it tells animals and human beings when to eat, sleep and wake.
Events outside the plants and animals affect the actions of some biological clocks. Scientists recently found, for example, that a tiny animal changes the color of its fur because the number of hours of daylight. In the short days of winter, its fur becomes white. The fur becomes gray brown in color in the longer hours of daylight in summer.
Inner signals control other biological clocks. German scientists found that some kind of internal clock seems to order birds to begin their long migration flight twice each year. Birds prevented from flying become restless when it is time for the trip, but they become calm again when the time of the flight has ended.
Scientists say they are beginning to learn which part of brain contains biological clocks. An American researcher, Martin Moorhead, said a small group of cells near the front of the brain seems to control the timing of some of our actions. These cells tell a person when to awaken,when to sleep and when to seek food. Scientists say there probably are other biological clock cells that control other body activities.
Dr. Moorhead is studying how our biological clocks affect the way we do our work. For example, most of us have great difficulty if we must change to different work hours.
It can take many days for a human body to accept the major change in work hours. Dr. Moorhead said industrial officials should have a better understanding of biological clocks and how many affect workers. He said such understanding could cut sickness and accidents at work and would increase a factory's production.
1. Which of the following is NOT only controlled by the biological clock itself?
A. Some animals change the color of its fur when season changes.
B. Insects break through cocoons and fly away.
C. Human beings know when to seek food.
D. Birds start their yearly migration flight.
2. Which of the following statements is true about the biological clocks?
A. Human hearts and brains contain biological clocks.
B. The biological clocks only tell a person when to sleep and when to seek food.
C. Events outside living things can sometimes affect the actions of some biological clocks.
D. Biological clocks control all the behaviors of living things.
3. A tiny animal changes the color of its fur because of _______.
A. the outside temperature B. sunshine hours
C. the lack of food D. the sudden fright
4. Birds prevented from flying become restless when it is time for the trip. The word "restless" can be best replaced by _______.
A. relaxed B. uneasy C. excited D. angry
5. The best title for this passage is _______.
A. Biological Signals B. Biological Changes
C. Biological Benefits D. Biological Clocks