GWD1-26

endless1990

  Recently biologists have been

         interested in a tide-associated

         periodic behavior displayed by

Line         the diatom Hantzschia virgata, a

  (5)       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

(10)       burrowed in the sand during high

tide, and emerge on the sand sur-

face during the daytime low tide.

Just before the sand is inundated by

the rising tide, the diatoms burrow

(15)       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

(20)       in pressure caused by tidal move-

         ment.  However, when diatoms are

         observed under constant conditions

in a laboratory, they still display

periodic behavior, continuing to bur-

(25)       row on schedule for several weeks.

This indicates that commuter diatoms,

rather than relying on environmental

cues to keep time, possess an inter-

nal pacemaker or biological clock

(30)       that enables them to anticipate peri-

odic changes in the environment.

A commuter diatom has an unusu-

         ally accurate biological clock, a

consequence of the unrelenting

(35)     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

(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.

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



point out a fundamental difference between the function of biological clocks in organisms and the use of mechanical clocks by humans
illustrate the way in which the period of an organism’s biological clock can be altered by environmental factors
suggest that there are important similarities between the biological clock in organisms such as the commuter diatom and the biological clock in humans
support an argument regarding the methods used by certain organisms to counteract the influence of the environment on their biological clocks
question the accuracy of the biological clock in organisms such as the commuter diatom

答案选B, 从文章中哪里可以看出？

xiexiang

楼主把这句话读一下看能解决不

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.  

另外再比较下几个选项也能排除一些了.呵呵

sumerlaws

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.

sumerlaws

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

hazardous

我选择了D.
能理解B的正确，但是想请高人指点D的错误之处。谢谢

endless1990

many  thanks z!!