This is not to suggest that the 40 period of this

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This is not to suggest that the (40) period of this biological clock is immutably fixed. Biologists have concluded that even though a diatom does not rely on the envi- ronment to keep time, environmental (45) factors—including changes in the tide’s hydrostatic pressure, salin- ity, mechanical agitation, and temperature—can alter the period of its biological clock according to (50) changes in the tidal cycle. In short, the relation between an organism’s biological clock and its environment is similar to that between a wristwatch and its owner: the owner cannot (55) make the watch run faster or slower, but can reset the hands. However, this relation is complicated in intertidal dwellers such as commuter diatoms by the fact that these organisms are (60) exposed to the solar-day cycle as well as to the tidal cycle, and some- times display both solar-day and tidal periods in a single behavior. Commuter diatoms, for example, (65) emerge only during those low tides that occur during the day. -------------------------------------------------------------------------------- Q23: The passage suggests which of the following about the accuracy of the commuter diatom’s biological clock? A. The accuracy of the commuter diatom’s biological clock varies according to changes in the tidal cycle. 23
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B. The unusual accuracy that characterizes the commuter diatom’s biological clock is rare among intertidal species. C. The commuter diatom’s biological clock is likely to be more accurate than the biological clock of a species that is subject to less intense environmental pressures. D. The commuter diatom’s biological clock tends to be more accurate than the biological clocks of most other species because of the consistency of the tidal cycle. E. The accuracy of the commuter diatom’s biological clock tends to fluctuate when the diatom is observed under variable laboratory conditions. Answer: -------------------------------------------------------------------------------- Q24: According to the passage, the periodic behavior displayed by commuter diatoms under constant laboratory conditions is characterized by which of the following? --------------------------------------------------------------------------------
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