GWD1-26

cckjenius

The author of the passage compares the relationship between an organism’s biological clock and its environment to the relation between a wristwatch and its owner most probably in order to

A.point out a fundamental difference between the function of biological clocks in organisms and the use of mechanical clocks by humans

B.illustrate the way in which the period of an organism’s biological clock can be altered by environmental factors

C.suggest that there are important similarities between the biological clock in organisms such as the commuter diatom and the biological clock in humans

D.support an argument regarding the methods used by certain organisms to counteract the influence of the environment on their biological clocks

E.question the accuracy of the biological clock in organisms such as the commuter diatom

答案是B，为什么不选D？D哪里错误？没有搜索到这道题的讨论帖，请大家指教~

原文如下:

GWD1-Q25 to Q28:
Recently biologists have been interested in a tide-associated periodic behavior displayed by the diatom Hantzschia virgata, a microscopic golden-brown alga that inhabits that portion of a shoreline washed by tides (the intertidal zone). Diatoms of this species, sometimes called “commuter” diatoms, remain burrowed in the sand during high tide, and emerge on the sand surface during the daytime low tide. Just before the sand is inundated by the rising tide, the diatoms burrow again.Some scientists hypothesize that commuter diatoms know that it is low tide because they sense an environmental change, such as an alteration in temperature or a change in pressure caused by tidal movement.However, when diatoms are observed under constant conditions in a laboratory, they still display periodic behavior, continuing to burrow on schedule for several weeks. This indicates that commuter diatoms, rather than relying on environmental cues to keep time, possess an internal pacemaker or biological clock that enables them to anticipate periodic changes in the environment. A commuter diatom has an unusually accurate biological clock, a consequence of the unrelenting environmental pressures to which it is subjected; any diatoms that do not burrow before the tide arrives are washed away.

This is not to suggest that the period of this biological clock is immutably fixed.Biologists have concluded that even though a diatom does not rely on the environment to keep time, environmental factors—including changes in the tide’s hydrostatic pressure, salinity, mechanical agitation, and temperature—can alter the period of its biological clock according to 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 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 exposed to the solar-day cycle as well as to the tidal cycle, and sometimes display both solar-day and tidal periods in a single behavior. Commuter diatoms, for example, emerge only during those low tides that occur during the day.

logowuyi

第二段一开始作者说生物钟并不是永远不变的，然后说虽然diatom这种藻类不依靠环

境来校准生物钟，环境的变化依然可以改变生物钟的周期。所以这种关系就像人和手表一

样，代表的人不能让手表的运行速度，但是可以改变手表的整体运行情况。所以作者打这

个比方其实是为了解释环境如何影响D海藻的生物钟周期，应该选B~~