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Biological functions of many plants and animals vary in cycles that

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Biological functions of many plants and animals vary in cycles that  [#permalink]

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New post 18 Jul 2008, 01:33
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A
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E

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Biological functions of many plants and animals vary in cycles that are repeated every 24 hours. It is tempting to suppose that alteration in the intensity of incident light is the stimulus that controls these daily biological rhythms. But there is much evidence to contradict this hypothesis.

Which of the following, if known, is evidence that contradicts the hypothesis stated in lines 2-5 above? (Bolded)


(A) Human body temperature varies throughout the day, with the maximum occurring in the late afternoon and the minimum in the morning.

(B) While some animals, such as the robin, are more active during the day, others, such as mice, show greater activity at night.

(C) When people move from one time zone to another,their biological rhythms adjust in a matter of days to the periods of sunlight and darkness in the new zone.

(D) Certain single-cell plants display daily biological rhythms even when the part of the cell containing the nucleus is removed.

(E) Even when exposed to constant light intensity around the clock, some algae display rates of photosynthesis that are much greater during daylight hours than at night.



The Official Guide for GMAT Review, 11th Edition, 2005

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Question No.: CR 72
Page: 488

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Re: Biological functions of many plants and animals vary in cycles that  [#permalink]

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New post 18 Jul 2008, 06:41
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Doesn't it explain that the livings actions' change is related with light therefore related with timing?

The official answer is E, yet about the logic I did not get anything. In E it explains algea is effected by sunlight so it does show many reactions in daylight than night. So if the question asks us to undermine not support the conclusion. There has to lie another logic.

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Re: Biological functions of many plants and animals vary in cycles that  [#permalink]

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New post 23 Jul 2008, 17:34
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Stated Hypothesis: Intensity of Incident light has direct relation to the biological rhythms.

The answer choice that weakens the hypothesis will introduce facts that varying intensity also produces the same rhythms effect or same light intensity produces varying rhythms.


(A) Human body temperature varies throughout the day, with the maximum occurring in the late afternoon and the minimum in the morning. [ Yes, supports the hypothesis – eliminate it]

(B) While some animals, such as the robin, are more active during the day, others, such as mice, show greater activity at night [ Direct or inverse relation – no effect]

(C) When people move from one time zone to another, their biological rhythms adjust in a matter of days to the periods of sunlight and darkness in the new zone. [Irrelevant – When biological rhythms get adjusted – eliminate it]

(D) Certain single-cell plants display daily biological rhythms even when the part of the cell containing the nucleus is removed. [irrelevant – eliminate it]

(E) Even when exposed to constant light intensity around the clock, some algae display rates of photosynthesis that are much greater during daylight hours than at night. [Hold it]

Answer: E
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Re: Biological functions of many plants and animals vary in cycles that  [#permalink]

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New post 18 Feb 2013, 03:53
Can we see the Reasoning behind the OA?
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Re: Biological functions of many plants and animals vary in cycles that  [#permalink]

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New post 18 Feb 2013, 04:06
plumber250 wrote:
Can we see the Reasoning behind the OA?


Situation:
Biological rhythms of many plans and animals work in 24 hr cycles. The alteration of the intensity of light is thought to control these cycles.

Reasoning:
What evidence the hypothesis that light is the controlling stimulus?
Look for an example demonstrating that the intensity of light cannot be the controlling stimulus of the 24 hr cycle. Algae exposed to a constant intensity of light throughout the 24 hr cycle nevertheless exhibit a far greater activity of biological functions during daylight hours than at night. The ex. of algae thus contradicts the hypothesis.
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Re: Biological functions of many plants and animals vary in cycles that  [#permalink]

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New post 21 Jul 2016, 13:45
shonakshi wrote:
Biological functions of many plants and animals vary in cycles that are repeated every 24 hours.It is tempting to suppose that alteration in the intensity of incident light is the stimulus that controls these biological rythms. But there is much evidence to contradict this hypothesis.

Which of the following is evidence that contradicts the hypothesis stated in line 2-5 above ?

A) Human body temperature varies throughout the day,with the maximum occurring in the late afternoon and the minimum in the morning.

B) While some animals,such as the robin,are more active during the day ,others,such as mice ,show greater activity at night.

C)When people move from one timezone to another,their daily biological rythms adjust in a matter of days to the periods of sunlight and darkness in the new zone.

D) Certain single-cell plants display daily biological rythms even when the part of the cell containing the nucleus is removed.

E) Even when exposed to constant light intensity around the clock,some algae display rates of photosynthesis that are much greater during daylight hours than at night


It is not clear what is meant by line 2-5. However I would presume (because the OA is E) that the hypothesis is: "alteration in the intensity of incident light is the stimulus that controls these biological rhythms."

Option E states the even under constant light intensity the biological rhythm follows the day-night cycle (and NOT the light intensity, if the rhythm followed light intensity the rate of photosynthesis would not change).

Following is a frequently used logic chain in GMAT:
Hypothesis: X causes Y.
Evidence: Z causes Y.
Therefore the evidence weakens / contradicts the Hypothesis.

Here,
X = alteration of light intensity
Y = biological rhythm
Z = day-night cycle
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Re: Biological functions of many plants and animals vary in cycles that  [#permalink]

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New post 21 Jul 2016, 14:48
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In simple terms you need an option that would show that biological functions are not dependent on sun light as told in the arguememt. If you see carefully, option E states that even on giving light for 24 hours .. algae were active during the day and not at night time.. hence it shows that sunlight is not the factor. Hence answer E.

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Re: Biological functions of many plants and animals vary in cycles that  [#permalink]

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New post 20 Apr 2017, 13:07
Biological functions of many plants and animals
vary in cycles that are repeated every 24 hours. It is
tempting to suppose that alteration in the intensity
of incident light is the stimulus that controls
these daily biological rhythms. But there is much
evidence to contradict this hypothesis.

Which of the following, if known, is evidence that contradicts the hypothesis stated in lines 2-5 above?

(A) Human body temperature varies throughout the day, with the maximum occurring in the late afternoon and the minimum in the morning.

- This option talks about the temperature impact on human body and nowhere mentions the impact of the light, hence this option is irrelevant.

(B) While some animals, such as the robin, are more active during the day, others, such as mice, show greater activity at night

- Once again, this option talk about day and night but we cannot conclude that light is playing a role in this behaviour. Hence, B is irrelevant too.


(C) When people move from one time zone to another, their biological rhythms adjust in a matter of days to the periods of sunlight and darkness in the new zone.
- Time zones is completely out of Scope.


(D) Certain single-cell plants display daily biological rhythms even when the part of the cell containing the nucleus is removed.
- Talks about biological rhythms but does not mention anything about light, once again out.


(E) Even when exposed to constant light intensity around the clock, some algae display rates of photosynthesis that are much greater during daylight hours than at night.

- This option is clearly taking into consideration the impact of light. It definitely weakens the argument.

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Re: Biological functions of many plants and animals vary in cycles that  [#permalink]

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New post 12 Nov 2017, 07:30
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Read the second part of the question carefully, "alteration" in the intensity...reason for the change in biological rhythms.
so we are concerned with the change in light intensity, be it any light.

option E clearly states that, even after providing "constant light intensity" exposure to algae, rates of photosynthesis (biological rhythms)...greater during daylight hours( we are speaking only of hours, the light intensity is still constant) than at NIGHT( whoa!! there is a variation in biological rhythms!!...who the hell did it, definitely not light intensity coz that was kept constant throughout!)
whoa!! again hypothesis overruled

hope you understood it.

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Re: Biological functions of many plants and animals vary in cycles that  [#permalink]

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Re: Biological functions of many plants and animals vary in cycles that   [#permalink] 08 Apr 2019, 04:02
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