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Recently biologists have been interested in a [#permalink]

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26 Jul 2012, 20:38
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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.

Q25: The passage suggests which of the following about the accuracy of the commuter diatom’s biological clock?

A: The accuracy of the commuter diatom’s biological clock varies according to changes in the tidal cycle.
B: The unusual accuracy that characterizes the commuter diatom’s biological clock is rare among intertidal species.
C: 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.
D: 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.
E: The accuracy of the commuter diatom’s biological clock tends to fluctuate when the diatom is observed under variable laboratory conditions.
[Reveal] Spoiler:
C

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
[Reveal] Spoiler:
B

Q27: According to the passage, the periodic behavior displayed by commuter diatoms under constant laboratory conditions is characterized by which of the following?

A: Greater unpredictability than the corresponding behavior under natural conditions
B: A consistent periodic schedule in the short term
C: No difference over the long term from the corresponding behavior under natural conditions
D: Initial variability caused by the constant conditions of the laboratory
E: Greater sensitivity to environmental factors than is the case under natural conditions
[Reveal] Spoiler:
B

28: The primary purpose of the passage is to

A: dispute the influence of environmental factors on the tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata
B: describe how certain tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata have changed over time
C: compare tide-associated behavioral rhythms to solar-day behavioral rhythms in the diatom Hantzschia virgata
D: examine how certain biological and environmental influences affect the tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata
E: identify certain environmental factors that limit the effectiveness of the biological clock in the diatom Hantzschia virgata
[Reveal] Spoiler:
D

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

A. It is triggered when the diatoms are inundated by the tide
B.It is correlated with the rise and fall of the tide
C. It adjusts to changes in the tidal cycle
D.It is influenced by the solar-day cycle
E.It is regulated by an innate time-keeping mechanism
[Reveal] Spoiler:
A

Which of the following can be inferred from the passage about the effect of the solar-day cycle on the tide-associated periodic behavior displayed by commuter diatoms?

A The solar-day cycle makes this behavior less advantageous to the commuter diatoms at certain times of the year.
B The solar-day cycle makes this behavior somewhat more erratic.
C The solar-day cycle makes this behavior less important to the survival of the commuter diatoms.
D Because of the solar-day cycle, this behavior is forced to proceed at a more rapid pace at certain times during the 24-hour day.
E Because of the solar-day cycle, this behavior is not expressed at certain times during the 24-hour day.
[Reveal] Spoiler:
E

[Reveal] Spoiler: Question #1 OA
[Reveal] Spoiler: Question #2 OA
[Reveal] Spoiler: Question #3 OA
[Reveal] Spoiler: Question #4 OA
[Reveal] Spoiler: Question #5 OA
[Reveal] Spoiler: Question #6 OA

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Last edited by JarvisR on 24 Jun 2015, 07:36, edited 4 times in total.
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Re: Recently biologists have been interested in a [#permalink]

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26 Jul 2012, 21:36
My Answers are as follows. What are the OAs

25. A
26. B
27. A
28. D
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Re: Recently biologists have been interested in a [#permalink]

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26 Jul 2012, 22:31
I'll go with CBCA here. I may chime in again with reasoning after others have had a chance
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Re: Recently biologists have been interested in a [#permalink]

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27 Jul 2012, 13:59
uledssul wrote:
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.

Q25:
The passage suggests which of the following about the accuracy of the commuter diatom’s biological clock?

The accuracy of the commuter diatom’s biological clock varies according to changes in the tidal cycle. NOT ONLY
The unusual accuracy that characterizes the commuter diatom’s biological clock is rare among intertidal species. NOT MENTIONED
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.
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. NOT MENTIONED
The accuracy of the commuter diatom’s biological clock tends to fluctuate when the diatom is observed under variable laboratory conditions. FALSE IS STABLE

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 OUT OF SCOPE
illustrate the way in which the period of an organism’s biological clock can be altered by environmental factors IS THE PHRASE JUST BEFORE IN SHORT,.....
suggest that there are important similarities between the biological clock in organisms such as the commuter diatom and the biological clock in humans NOT MENTIONED
support an argument regarding the methods used by certain organisms to counteract the influence of the environment on their biological clocks WE COUNTERACT .........NOTHING
question the accuracy of the biological clock in organisms such as the commuter diatom OUT OF SCOPE

Q27:
According to the passage, the periodic behavior displayed by commuter diatoms under constant laboratory conditions is characterized by which of the following?

Greater unpredictability than the corresponding behavior under natural conditions FALSE
A consistent periodic schedule in the short term FALSE (SEVERAL WEEKS)
No difference over the long term from the corresponding behavior under natural conditions
Initial variability caused by the constant conditions of the laboratory FALSE
Greater sensitivity to environmental factors than is the case under natural conditions NOT ONLY IS A SINERGY AND MORE

28:
The primary purpose of the passage is to

dispute the influence of environmental factors on the tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata
describe how certain tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata have changed over time OUT OF SCOPE
compare tide-associated behavioral rhythms to solar-day behavioral rhythms in the diatom Hantzschia virgata NOT ONLY
examine how certain biological and environmental influences affect the tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata TO VAGUE
identify certain environmental factors that limit the effectiveness of the biological clock in the diatom Hantzschia virgata TO SPECIFIC

The OA is CBBD

CBCA
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Re: Recently biologists have been interested in a [#permalink]

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28 Jul 2012, 06:51
CBCA
interesting passage.OA Please?
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Re: Recently biologists have been interested in a [#permalink]

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30 Jul 2012, 17:03
Even though is really strange. I mean: I have ALL the RC pubblication by Aristotle prep: RC99 and RC Practice Set 1 and 2 and I didn't find this passage.
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Re: Recently biologists have been interested in a [#permalink]

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31 Jul 2012, 03:04
My answers are C B B A

my 3rd answer was B because, I considered several weeks as short period as things changed after a while. I took the below
Quote:
This is not to suggest that the period of this biological clock is immutably fixed.

to believe that things changed after some time. I did not bother to go back. this might have made me choose C
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Re: Recently biologists have been interested in a [#permalink]

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26 Nov 2012, 09:16
Can someone please explain why C in Q25?
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Re: Recently biologists have been interested in a [#permalink]

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02 Dec 2013, 21:49
OA are C, n\a, B, D.
Just got it at GMAT Prep 4th Exam.
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Re: Recently biologists have been interested in a [#permalink]

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07 Feb 2014, 22:01
rjacobsMGMAT wrote:
I'll go with CBCA here. I may chime in again with reasoning after others have had a chance

Hi
Please explain.....

My take is "ABCB".
whts the OA and OE????

Rgds
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Re: Recently biologists have been interested in a [#permalink]

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24 Jun 2015, 07:41
Hello from the GMAT Club VerbalBot!

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Re: Recently biologists have been interested in a [#permalink]

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25 Jun 2015, 09:34
Time taken 11mins:
Q2 and 6 got wrong.

Q25: The passage suggests which of the following about the accuracy of the commuter diatom’s biological clock?

A: The accuracy of the commuter diatom’s biological clock varies according to changes in the tidal cycle.
B: The unusual accuracy that characterizes the commuter diatom’s biological clock is rare among intertidal species.
C: 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.
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.

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

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
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

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

Q27: According to the passage, the periodic behavior displayed by commuter diatoms under constant laboratory conditions is characterized by which of the following?

A: Greater unpredictability than the corresponding behavior under natural conditions
B: A consistent periodic schedule in the short term
C: No difference over the long term from the corresponding behavior under natural conditions
D: Initial variability caused by the constant conditions of the laboratory
E: Greater sensitivity to environmental factors than is the case under natural conditions
>> I was inclined towards C. Appreciate inputs on this one.

28: The primary purpose of the passage is to

A: dispute the influence of environmental factors on the tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata
B: describe how certain tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata have changed over time
C: compare tide-associated behavioral rhythms to solar-day behavioral rhythms in the diatom Hantzschia virgata
D: examine how certain biological and environmental influences affect the tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata
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

E: identify certain environmental factors that limit the effectiveness of the biological clock in the diatom Hantzschia virgata

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

A. It is triggered when the diatoms are inundated by the tide
B.It is correlated with the rise and fall of the tide
C. It adjusts to changes in the tidal cycle
D.It is influenced by the solar-day cycle
E.It is regulated by an innate time-keeping mechanism

Which of the following can be inferred from the passage about the effect of the solar-day cycle on the tide-associated periodic behavior displayed by commuter diatoms?

A The solar-day cycle makes this behavior less advantageous to the commuter diatoms at certain times of the year.
B The solar-day cycle makes this behavior somewhat more erratic.
C The solar-day cycle makes this behavior less important to the survival of the commuter diatoms.
D Because of the solar-day cycle, this behavior is forced to proceed at a more rapid pace at certain times during the 24-hour day.
E Because of the solar-day cycle, this behavior is not expressed at certain times during the 24-hour day.
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.
......
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.

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Re: Recently biologists have been interested in a [#permalink]

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05 Aug 2015, 11:33
mikemcgarry
Can you please tell me why the answer to Q27 is B and not C. I chose C and in the posts even carcass has written that it's C explaining in brief but it's also told that the official answer is B. Can you please explain.

Thanks
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Re: Recently biologists have been interested in a [#permalink]

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02 Sep 2015, 05:22
vik09 wrote:
mikemcgarry
Can you please tell me why the answer to Q27 is B and not C. I chose C and in the posts even carcass has written that it's C explaining in brief but it's also told that the official answer is B. Can you please explain.

Thanks

The passage clearly says >>
However, when diatoms are observed under constant conditions in a laboratory, they still display periodic behavior, continuing to burrow on schedule for several weeks.

continuing to burrow on schedule for several weeks >>> This tells us that they will continue the behavior for some limited time after they are are moved from outside to laboratory...
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Re: Recently biologists have been interested in a [#permalink]

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24 Apr 2016, 06:04
This one is a passage of Exam pack 1. (CAT 3)
Is it really a sub-600 passage?
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Re: Recently biologists have been interested in a [#permalink]

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01 Jun 2016, 17:06
JarvisR For #29, why is it not B (with rise and fall of a tide?) We know tidal affects it but not sure the tide rise and fall does?
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Re: Recently biologists have been interested in a [#permalink]

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08 Aug 2016, 01:50
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Good passage with fairly easy answers except for QUESTION 27 which is very iffy.

The answer can be B or C depending upon how the reader perceives period of time.

In evolutionary sense, several weeks are nothing more than a milliseconds because evolution takes place over hundreds of thousands of year. This behaviour of diatoms have evolved over thousands of years.

In real life sense for scientific studies, one can argue that several weeks is a considerable time, given that some experiments such as the generation of Higgs boson in a large particle collider last for one millionth of a second.

IN MY OPINION QUESTION 27 is a bit ambiguous. If the passage has mentioned some terms like evolution or hundred of years or something like that to give an idea about the time then B would have made more sense. But since the passage is talking about every day cycle , 24 hour cycle, low tides and high tides, diurnal cycles (day and night) etc etc, all of which are short term phenomenon's therefore going with option C makes more sense.

SO NOT HAPPY ABOUT QUESTION 27
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Re: Recently biologists have been interested in a [#permalink]

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26 Aug 2016, 20:07
LogicGuru1 wrote:
Good passage with fairly easy answers except for QUESTION 27 which is very iffy.

The answer can be B or C depending upon how the reader perceives period of time.

In evolutionary sense, several weeks are nothing more than a milliseconds because evolution takes place over hundreds of thousands of year. This behaviour of diatoms have evolved over thousands of years.

In real life sense for scientific studies, one can argue that several weeks is a considerable time, given that some experiments such as the generation of Higgs boson in a large particle collider last for one millionth of a second.

IN MY OPINION QUESTION 27 is a bit ambiguous. If the passage has mentioned some terms like evolution or hundred of years or something like that to give an idea about the time then B would have made more sense. But since the passage is talking about every day cycle , 24 hour cycle, low tides and high tides, diurnal cycles (day and night) etc etc, all of which are short term phenomenon's therefore going with option C makes more sense.

SO NOT HAPPY ABOUT QUESTION 27

Hi,
And i'm happy with your reasoning. That's exactly what was in my mind when I solve this question, though not as detail as yours. I got C too.
Any one here can give a reasonable explanation about the "short term" and "long term" in B and C please? Thanks in advance.
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Re: Recently biologists have been interested in a [#permalink]

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27 Aug 2016, 22:35
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The passage states that the diatoms continue to burrow on a periodic schedule for several weeks. This means that either the observation period only lasted a few weeks or the behavior changed after those few weeks. The latter seems more likely, otherwise the author should make it clear that the behavior persisted for the entire observation period. Similarly, if the diatoms all died off after those few weeks, the language used would be deceptive. In the end, what we know is that the behavior was not something that continued for a long time on the scientists' scale. This tells us that we have a short-term and not a long-term observation.

Another problem with C is its extreme nature. It says that there is "no difference" from the behavior that occurs under natural conditions. We have no idea about this. It seems quite plausible that the burrowing could be, for instance, shallower or less thorough. We'd have to know more to conclude that there is no difference in the long term. In any case, if there were never going to be a difference, then B would be correct, too! "Long term" is a higher standard to prove than "short term." There's no indication that there is an adjustment period, so if we have long term, we also have short term.
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Re: Recently biologists have been interested in a   [#permalink] 27 Aug 2016, 22:35
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