GWD4-Q25:

cjyc1

Recently biologists have been

       interested in a tide-associated

       periodic behavior displayed by

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                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.

 

GWD4-Q25:  

According to the passage, each of the following is characteristic of the tide-associated periodic behavior of commuter diatoms EXCEPT:

             

1. It is triggered when the diatoms are inundated by the tide.
2. It is correlated with the rise and fall of the tide.
3. It adjusts to changes in the tidal cycle.
4. It is influenced by the solar-day cycle.
5. It is regulated by an innate time-keeping mechanism.

 

 

答案是A，我的答案是D

cjyc1

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.

这段话的意思是什么，有点看不懂？里面的commuter diatoms跟上文谈到的不是一个种类的吗？

SMcollapse

就是讲影响commuter diatom周期变化的一个大段话
我总结的这种句子，与文章主体没什么关系的句子出现在文中就是为了出题用的
这种句子要着重看
当然往往也是让我们觉得读得很迷茫的句子