GMAT Critical Reasoning
Biological functions of many plants and animals vary in cycles that are repeated every 24 hours. It is tempting to suppose that alteration in the intensity of incident light is the stimulus that controls these daily biological rhythms. But there is much evidence to contradict this hypothesis.
Which of the following, if known, is evidence that contradicts the hypothesis stated in the lines above?
- A Human body temperature varies throughout the day, with the maximum occurring in the late afternoon and the minimum in the morning.
- B While some animals, such as the robin, are more active during the day, others, such as mice, show greater activity at night.
- C When people move from one time zone to another, their daily biological rhythms adjust in a matter of days to the periods of sunlight and darkness in the new zone.
- D Certain single-cell plants display daily biological rhythms even when the part of the cell containing the nucleus is removed.
- E Even when exposed to constant light intensity around the clock, some algae display rates of photosynthesis that are much greater during daylight hours than at night.
Correct Answer: E