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. GWD1-Q26:
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
The ANS is B. But why d is incorrect? is there no argument in the passage?
thanks for your explaination in advance.
GWD1-Q26:
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
The ANS is B. But why d is incorrect? is there no argument in the passage?
thanks for your explaination in advance. 作者: chipmunk 时间: 2011-9-16 06:29
IN GMAT , I usually go to the front content ,namely front sentence ,to find out the correct answer. GMAC has a tendency to make the correct answer just closely come before the very question .In this question, B perfectly explain the question , B option is a simplified sentence of the first sentence of the phase.while in D , it claims that that behavior is a act to counteract the influence of the environment , I wanna say , in passage the author did not mention the "counteract things " at all . The D goes too far to illustrate the question from its perspective. the author just try to describe how these plant adapt to the change of surroundings .
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