gwd1-25&27&28

这两题完全没概念的说！

Q25 to Q28:

      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.

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Q25:

The passage suggests which of the following about the accuracy of the commuter diatom’s biological clock?

1. The accuracy of the commuter diatom’s biological clock varies according to changes in the tidal cycle.


2. The unusual accuracy that characterizes the commuter diatom’s biological clock is rare among intertidal species.


3. 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.


4. 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.


5. The accuracy of the commuter diatom’s biological clock tends to fluctuate when the diatom is observed under variable laboratory conditions.
   

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Q27:

According to the passage, the periodic behavior displayed by commuter diatoms under constant laboratory conditions is characterized by which of the following?

1. Greater unpredictability than the corresponding behavior under natural conditions


2. A consistent periodic schedule in the short term


3. No difference over the long term from the corresponding behavior under natural conditions


4. Initial variability caused by the constant conditions of the laboratory


5. Greater sensitivity to environmental factors than is the case under natural conditions

25. c,  27. C (underlined information)

27 选B，L25 for several week

此外：

GWD-1-Q28:

The primary purpose of the passage is to

1. dispute the influence of environmental factors on the tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata

2. describe how certain tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata have changed over time

3. compare tide-associated behavioral rhythms to solar-day behavioral rhythms in the diatom Hantzschia virgata

4. examine how certain biological and environmental influences affect the tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata

5. identify certain environmental factors that limit the effectiveness of the biological clock in the diatom Hantzschia virgata

答案E，本帅不敢苟同！E生物钟的effectiveness 受到environmental factors 限制，显然不是。effectiveness 是说发挥的正常不正常。

我选D。你的意见呢？

A commuter diatom has an unusu-

       ally accurate biological clock, a

consequence of the unrelenting

(35)       environmental pressures to which

it is subjected。

27，b。 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

Q28:

The primary purpose of the passage is to

1. dispute the influence of environmental factors on the tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata
2. describe how certain tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata have changed over time
3. compare tide-associated behavioral rhythms to solar-day behavioral rhythms in the diatom Hantzschia virgata
4. examine how certain biological and environmental influences affect the tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata
5. identify certain environmental factors that limit the effectiveness of the biological clock in the diatom Hantzschia virgata

28题答案是D， 但我选A， 关于生物钟， 我在文中只找到biological infulences， 实在没看到关于environmental influences 。 郁闷中， 请赐教。

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.

Could someone post the question 26 and the answer? I do not have it.

Thanks a lot!!!谢谢谢谢谢