Paragraph 2：When crayfish are kept continuously in the dark, even for four
to five months, their compound eyes continue to adjust on a daily schedule
for daytime and nighttime vision. Horseshoe crabs kept in the dark
continuously for a year were found to maintain a persistent rhythm of brain
activity that similarly adapts their eyes on a daily schedule for bright or
for weak light. Like almost all daily cycles of animals deprived of
environmental cues, those measured for the horseshoe crabs in these
conditions were not exactly 24 hours. Such a rhythm whose period is
approximately—but not exactly—a day is called circadian. For different
individual horseshoe crabs, the circadian period ranged from 22.2 to 25.5
hours. A particular animal typically maintains its own characteristic cycle
duration with great precision for many days. Indeed, stability of the
biological clock's period is one of its major features, even when the
organism's environment is subjected to considerable changes in factors, such
as temperature, that would be expected to affect biological activity
strongly. Further evidence for persistent internal rhythms appears when the
usual external cycles are shifted—either experimentally or by rapid
east-west travel over great distances. Typically, the animal's daily
internally generated cycle of activity continues without change. As a result,
its activities are shifted relative to the external cycle of the new
environment. The disorienting effects of this mismatch between external time
cues and internal schedules may persist, like our jet lag, for several days
or weeks until certain cues such as the daylight/darkness cycle reset the
organism's clock to synchronize with the daily rhythm of the new environment.
6. According to paragraph 2, which of the following is true about the
circadian periods of animals deprived of environmental cues?
○ They have the same length as the daily activity cycles of animals that are
not deprived of such cues.
○ They can vary significantly from day to day.
○ They are not the same for all members of a single species.
○ They become longer over time.
答案是C，但我想問為什麼A不行? 而且我覺得not the same for all members of a
single species從文中能知道是horseshoe crabs而已....
另外還想問第14題，答案是126，但我不知道為什麼4不行選?
文章中不是有說即使沒有environmental cues，動物還是可以依據自己的生理時鐘作息嗎?
謝謝解答:)
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