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Recently biologists have been interested in a

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

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New post 03 Nov 2017, 00:19
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.

[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



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 [#permalink]

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New post 10 Dec 2017, 01:48
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   [#permalink] 10 Dec 2017, 01:48

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