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Recently biologists have been interested in a tide-associated periodic

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Recently biologists have been interested in a tide-associated periodic  [#permalink]

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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.


1. 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.



2. 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



3. 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



4. 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



5. 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



6. 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.



JOURNAL ARTICLE
Time, Tide and the Living Clocks of Marine Organisms
John D. Palmer
American Scientist
Vol. 84, No. 6 (NOVEMBER-DECEMBER 1996), pp. 570-578
Published by: Sigma Xi, The Scientific Research Honor Society
Stable URL: https://www.jstor.org/stable/29775786
Page Count: 9

SCIENTIFIC AMERICAN
February 1975
Volume 232, Issue 2[/b]

Biological Clocks of the Tidal Zone
Endogenous clocks set to the rhythm of the solar day are known throughout the biological world. Many organisms that live along the shore also have a clock set to the rhythm of the lunar day

By John D. Palmer

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Originally posted by uledssul on 26 Jul 2012, 21:38.
Last edited by SajjadAhmad on 05 Aug 2019, 03:53, edited 9 times in total.
Updated complete topic (79).
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Re: Recently biologists have been interested in a tide-associated periodic  [#permalink]

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New post 25 Jun 2015, 10:34
3
3
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 tide-associated periodic  [#permalink]

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New post 27 Jul 2012, 14:59
1
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



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Re: Recently biologists have been interested in a tide-associated periodic  [#permalink]

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New post 08 Aug 2016, 02:50
1
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 tide-associated periodic  [#permalink]

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New post 27 Aug 2016, 23:35
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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 tide-associated periodic  [#permalink]

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New post 03 Nov 2017, 01:19
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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?


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.



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



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



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



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.




Taking this passage step by step

Question 1
A- be careful because the "accuracy" of the clock is not quite affected by changes in the tidal cycle- rather the time is "set" by the tidal waves. For example, tidal waves in California are what would set the alga's behavior to Western Shore time. False
B- Maybe. But the passage more explicitly supports another answer
C- The passage clearly states that the accuracy of the alga's biological is a result of environmental pressures. If we can negate that we can infer that low environmental pressure would lead to a less accurate clock because of the absence of a necessary precondition or even sufficient condition.
D- No because as in C the passage states a particular reason for by the alga's clock is so accurate
E- This contradicts the passage

Question 2
A The author is trying to explain how alga's clock can be controlled by some external factor- which is not what A states
B Yes
C The point of the analogy is not to draw a parallel between the biological clocks of alga and those of humans. The analogy is trying to explain that the clock is controlled by some external factor as is a clock; the external factor controlling a clock is the person setting it and the person setting it is analogous to the environemtn
D This is counterintuitive to the passage because the passage is saying that the biological clocks of alga are a defense mechanism that has developed as a natural result of environmental pressures; the clock is controlled by environmental factors which work to the alga's advantage
E The issue at point is not the accuracy of the clocks- the point of the analogy is to explain how the controlling mechanism of a clock and the biological clock of an alga are similar

Question 3
A contradicts passage
B correct
C contradicts passage
D contradicts passage
E contradicts passage

Question 4
A The passage is supporting the influence of environmental factors on alga's biological clock rather than disputing it
B Where does the passage say this? There's only sentence that explains the clock is an evolutionary feature but of course that's clearly too narrow
C This only mentioned briefly. Too narow
D Correct
E The passage doesn't even support this generalization

Question 5
A Correct through POE and because it is also simply unsupported
B Stated in passage
C Stated in passage
D Stated in passage
E Stated in passage

Question 6
A Passage doesn't state this
B No. On the contrary the solar-day cycle is responsible for a consistent pattern of behavior in alga
C The passage doesn't mention this
D Passage doesn't mentioned this
E Correct
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Re: Recently biologists have been interested in a tide-associated periodic  [#permalink]

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New post 10 Dec 2017, 02:48
2
Interesting passage. Took 11 mins , including 4 mins to read the passage . All correct .

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

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
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.
B: illustrate the way in which the period of an organism’s biological clock can be altered by environmental factors


Q27: According to the passage, the periodic behavior displayed by commuter diatoms under constant laboratory conditions is characterized by which of the following?
However, when diatoms are observed under constant conditions in a laboratory, they still display periodic behavior, continuing to burrow on schedule for several weeks.

A: Greater unpredictability than the corresponding behavior under natural conditions -- Incorrect
B: A consistent periodic schedule in the short term -- Correct
C: No difference over the long term from the corresponding behavior under natural conditions -- Not sure -- May or may not be true-- but we are told only about several weeks
D: Initial variability caused by the constant conditions of the laboratory -- Incorrect
E: Greater sensitivity to environmental factors than is the case under natural conditions -- Incorrect


28: The primary purpose of the passage is to

D: examine how certain biological and environmental influences affect the tide-associated behavioral rhythms displayed by the diatom Hantzschia virgata -- Correct


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

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.

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

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?

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.

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. - Correct
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Re: Recently biologists have been interested in a tide-associated periodic  [#permalink]

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New post 29 Jan 2018, 19:11
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MSarmah wrote:
Can somebody explain what is wrong with option A in question no. 25 ??


Answer choice A of question 25 is incorrect because it is not the “accuracy of the biological clock” that varies according to the change in the tidal cycle. The biological clock just adapts itself to the new tidal cycle. The ability to adapt to new tidal cycle and to maintain that new cycle is again accurately managed by the biologic clock.

Hope this helps :-)
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Re: Recently biologists have been interested in a tide-associated periodic  [#permalink]

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New post 23 Feb 2019, 18:45
Hi GMATNinja,

I was wondering could you please go over Q6? Though I answered this question correctly, I was only able to reach the correct answer by poe. If you could please run through each of the options, I would greatly appreciate it!
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Re: Recently biologists have been interested in a tide-associated periodic  [#permalink]

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New post 11 Mar 2019, 01:00
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JS1290 wrote:
Hi GMATNinja,

I was wondering could you please go over Q6? Though I answered this question correctly, I was only able to reach the correct answer by poe. If you could please run through each of the options, I would greatly appreciate it!

Using process of elimination is a good thing, so if it worked for you here, awesome. We can run through the whole question anyway, though. Let's get a solid understanding of the relevant piece of the passage and then go through the answer choices.

Take a look at the end of the last paragraph of the passage:
Quote:
Commuter diatoms... 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.

The "single behavior" referenced in the passage is the commuter diatom's emergence onto the surface of the sand. This behavior is influenced by two factors:

  • Tidal period: Diatoms only emerge onto the surface of the sand during low tide.
  • Solar-day cycle: Diatoms only emerge onto the surface of the sand during low tides that occur during the day.

So the tidal period restricts the emergence of diatoms onto the surface of the sand to low tide, and the solar-day cycle further restricts this behavior to only occur during daytime low tides.

Now, apply this understanding to question 6:
Quote:
6. 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?


Quote:
(A) The solar-day cycle makes this behavior less advantageous to the commuter diatoms at certain times of the year.

The passage tells us that diatoms only emerge from the sand during certain times of day, but gives us no information about how this might affect diatoms at different times of the year. We have no way of inferring that the solar-day cycle would make the diatom's behavior less advantageous based on the time of year, so (A) is out.

Quote:
(B) The solar-day cycle makes this behavior somewhat more erratic.

The solar-day cycle certainly affects the tide-associated behavior, but does it make that behavior more erratic? The passage tells us that commuter diatoms only emerge during daytime low tides -- this is a highly predictable pattern, and definitely does not fit the description of a "somewhat more erratic" behavior. Eliminate (B).

Quote:
(C) The solar-day cycle makes this behavior less important to the survival of the commuter diatoms.

The passage tells us that the solar-day cycle restricts diatoms to emerge only during the day. However, there is no information that would allow us to infer that this restriction changes how important emerging onto the sand is for the survival of the diatoms. For this reason, answer choice (C) is out.

Quote:
(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.

According to this answer choice, the diatoms would emerge onto the sand at a more rapid pace at some times of day than at others. However, the passage merely tells us that the diatoms would not emerge at all unless it was daytime. Because we have no information about the actual speed at which the diatoms emerge, we cannot infer that the solar-day cycle forces them to emerge more rapidly at certain times of day. (D) is out.

Quote:
(E) Because of the solar-day cycle, this behavior is not expressed at certain times during the 24-hour day.

This is more like it! The passage tells us that diatoms emerge onto the sand during low tide. However, because diatoms are also influenced by the solar-day cycle, they only emerge onto the sand during low tides that occur during the day time. In is easy to infer from these facts that because of the solar-day cycle, the diatoms do not emerge onto the sand at certain times during the 24-hour day. (E) is the correct answer for question 6.

I hope that helps!
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Re: Recently biologists have been interested in a tide-associated periodic  [#permalink]

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New post 14 Apr 2019, 11:00
Hello GMAT experts GMATNinja Sir, VeritasKarishma ma'am,

Could you please help me with Q1 ( The passage suggests which of the following about the accuracy of the commuter diatom's biological clock)
I chose option A, but looking carefully I see why it is wrong.

Can you please help me with my reasoning ( is it correct or not):
Is option A wrong because it says the accuracy VARIES but as per the option it is the time or mechanism of the BIOLOGICAL CLOCK that varies and accuracy remains same?

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Re: Recently biologists have been interested in a tide-associated periodic  [#permalink]

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New post 15 Apr 2019, 04:49
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rish2708 wrote:
Hello GMAT experts GMATNinja Sir, VeritasKarishma ma'am,

Could you please help me with Q1 ( The passage suggests which of the following about the accuracy of the commuter diatom's biological clock)
I chose option A, but looking carefully I see why it is wrong.

Can you please help me with my reasoning ( is it correct or not):
Is option A wrong because it says the accuracy VARIES but as per the option it is the time or mechanism of the BIOLOGICAL CLOCK that varies and accuracy remains same?

Regards,
Rishav


Question 1:

(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.

We can infer (C) from the last sentence of paragraph 1: "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."

So we can say that commuter diatom's clock is likely to be more accurate than that of another species that is not subject to such intense environment.
Answer (C)


(A) is not correct.

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

"environmental factors -...- can alter the period of its biological clock according to changes in the tidal cycle"

According to changes in tidal cycle, the period of the clock varies, not its accuracy.
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Re: Recently biologists have been interested in a tide-associated periodic   [#permalink] 15 Apr 2019, 04:49
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