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[x1] : 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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Q28:
The primary purpose of the passage is to
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gwd里,答案是d,在新东方阅读教程里答案是a,求助各位大侠,究竟该选哪个??
MY 2 cents, key is D
GWD-1-Q28:
The primary purpose of the passage is to
我还是觉得这题应该选A,因为原文第一段说有这么一种现象,科学家假设这是因为环境造成的,所以做了一个实验,但实验结果表明不是环境造成了这个现象;第二段说虽然如此,但环境因素也还是有一定作用的。
所以文章整体都是围绕环境因素展开论述的,dispute不是反对,而是争论的意思,
C选项中的certain biological influences 感觉与原文中的biological clock有差别,而且原文中只提到了生物钟这一种,没有其他的,怎么可以用复数呢??我认为A和C最大的不对是文章讲了两个方面,一个是生物钟的作用,一个是环境因素对生物钟的影响。而A和C只讲了其中的一个方面。primary purpose应该把两个方面都放在上面才对。
清NN指教
MY 2 cents, key is D
GWD-1-Q28:
The primary purpose of the passage is to
同意!
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