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# Amphibian populations are declining in numbers worldwide.

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Amphibian populations are declining in numbers worldwide. [#permalink]

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13 Feb 2011, 15:48
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Amphibian populations are declining in numbers worldwide. Not coincidentally, the earth’s ozone layer has been continuously depleted throughout the last 50 years. Atmospheric ozone blocks UV-B, a type of ultraviolet radiation that is continuously produced by the sun, and which can damage genes. Because amphibians lack hair, hide, or feathers to shield them, they are particularly vulnerable to UV-B radiation. In addition, their gelatinous eggs lack the protection of leathery or hard shells. Thus, the primary cause of the declining amphibian population is the depletion of the ozone layer.

Each of the following, if true, would strengthen the argument EXCEPT:

(A) Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes.
(B) Amphibian populations are declining far more rapidly than are the populations of nonamphibian species whose tissues and eggs have more natural protection from V-B.
(C) Atmospheric ozone has been significantly depleted above all the areas of the world in which amphibian populations are declining.
(D) The natural habitat of amphibians has not become smaller over the past century.
(E) Amphibian populations have declined continuously for the last 50 years.

I don't agree with the OE:
[Reveal] Spoiler:
OE: A is the correct answer. "The answer fails to shed any light -positive or negative- on the connection between the ozone depletion and the amphibian population decline. Because the argument is concerned with the damage done by UV-B radiation, the fact that UV-B is the only damaging type of radiation blocked by ozone is irrelevant".
What would happen if there were other rays which are killing the amphibian populations? If other rays were the culprit, I think that the argument would be hurted in certain way. What do you think?

Source:CR Powerscore
[Reveal] Spoiler: OA

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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13 Feb 2011, 23:22
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Its A Vs D. Since rest strengthen the conclusion. I will try to answer why D is not the answer. For any causal argument X->Y any alt cause will weaken the argument. D says that the alt cause does not exist and laso that the effect does not exist before the cause. If the natural habitat were not endangered before. D is OUT, Which makes A as the answer. Under pressure just don't think why answer is an answer - mark the answer and move on. Over-analysis is a trap of gmat.

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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14 Feb 2011, 02:57
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IMO the choice is between A and B. others obviously help strengthen the argument.

If we look at B, we'll see B says other animals which are safer from UV-B rays don't have any decline. which, when paraphrased means UV-B rays are the factor behind the decline(which is another way of saying "Because amphibians lack hair, hide, or feathers to shield them, they are particularly vulnerable to UV-B radiation" as stated in the premise). we know "Atmospheric ozone blocks UV-B, a type of ultraviolet radiation that is continuously produced by the sun, and which can damage genes." so if UV-B rays are a factor, then indirectly, the depletion of ozone layer, which allowed the UV-B rays to enter is the cause. So it is STRENGTHENING.

Take A. "Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes" . if this is strengthening the argument then the opposite of this should weaken the argument. what is the opposite?? other type of radiations blocked by atmospheric ozone also cause damage. Now, what is the conclusion of the argument?? "Thus, the primary cause of the declining amphibian population is the depletion of the ozone layer." Is this conclusion weakened in any way by the previous statement?? no. the key here is "blocked by the atmospheric ozone". even if other radiation are the cause of decline, ozone layer depletion will allow those rays to enter and will therefore become an indirect cause. Either way ozone layer depletion is the cause of decline. this does not affect the conclusion. So A is clearly irrelevant, whether it is true or false, doesn't affect the conclusion.

Hence IMO A
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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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14 Feb 2011, 04:17
I agree with vinzycoolfire. B didnt caught me since its still heading south. I want a answer heading North. If someone says X is a better killer than Y - X and Y are both killers they are not saints. In any case life of the client will be endangered - still the arg is heading in one direction. Same here. Depletion of O layer is the culprit - which radiations in O layer is irrelevant hence A is OUT

Negation - that is awesome way. +1 to vinzycoolfire. The opposite of "only one" is some. Some of raditions besides X are causes of the population erosion. So what ? The arg is still on and says ozone is the real culprit. The arg is not negated when assum is. Hence it cannot be the real assumption / strengthener.

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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14 Feb 2011, 07:35
gmat1220 wrote:
Under pressure just don't think why answer is an answer - mark the answer and move on. Over-analysis is a trap of gmat.

Totally agree with you. Do that during the real exam or a practice CAT. However, during your routine preparation, you have to be sure why you are choosing an option.
That will increase your effectiveness. Otherwise, the chances will decide your score.
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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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15 Feb 2011, 02:27
IMO D
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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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07 Mar 2011, 10:37
What OE says about D? Why does it strengthen?

D) The natural habitat of amphibians has not become smaller over the past century.

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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30 Jan 2014, 17:53
magnolia wrote:
What OE says about D? Why does it strengthen?

D) The natural habitat of amphibians has not become smaller over the past century.

I am wondering the same thing. Bump.

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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01 Feb 2014, 02:44
I go with D,can someone explain why it's not correct?...OA says A

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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01 Feb 2014, 03:22
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karanwalia wrote:
I go with D,can someone explain why it's not correct?...OA says A

D is actually strengthening. It says that the natural habitat has not shrunk. If natural habitat had shrunk then we can attribute the reduction in population of amphibians to that and not to depleting Ozone.

A is correct, since it does not have any impact on the conclusion. This is very important difference between a weakener and strengthen except question. A weakener has to essentially attack the conclusion whereas 'strengthen except' or 'weaken except' does not have to do so necessarily. Even if it does not have any impact the answer is perfectly fine.

Hope its clear!
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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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24 Feb 2014, 10:37
ankur1901 wrote:
karanwalia wrote:
I go with D,can someone explain why it's not correct?...OA says A

D is actually strengthening. It says that the natural habitat has not shrunk. If natural habitat had shrunk then we can attribute the reduction in population of amphibians to that and not to depleting Ozone.

A is correct, since it does not have any impact on the conclusion. This is very important difference between a weakener and strengthen except question. A weakener has to essentially attack the conclusion whereas 'strengthen except' or 'weaken except' does not have to do so necessarily. Even if it does not have any impact the answer is perfectly fine.

Hope its clear!

I am still not able to understand why D is not the answer...since the natural inhabitat has not shrunk it means the ozone layer is not affecting the amphibians....thus weakening our conclusion and so it should be the answer

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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17 Mar 2014, 07:00
ankur1901 wrote:
karanwalia wrote:
I go with D,can someone explain why it's not correct?...OA says A

D is actually strengthening. It says that the natural habitat has not shrunk. If natural habitat had shrunk then we can attribute the reduction in population of amphibians to that and not to depleting Ozone.

A is correct, since it does not have any impact on the conclusion. This is very important difference between a weakener and strengthen except question. A weakener has to essentially attack the conclusion whereas 'strengthen except' or 'weaken except' does not have to do so necessarily. Even if it does not have any impact the answer is perfectly fine.

Hope its clear!

Chose A but not convinced with D.

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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10 Aug 2014, 03:44
AnmolKukreja wrote:
ankur1901 wrote:
karanwalia wrote:
I go with D,can someone explain why it's not correct?...OA says A

D is actually strengthening. It says that the natural habitat has not shrunk. If natural habitat had shrunk then we can attribute the reduction in population of amphibians to that and not to depleting Ozone.

A is correct, since it does not have any impact on the conclusion. This is very important difference between a weakener and strengthen except question. A weakener has to essentially attack the conclusion whereas 'strengthen except' or 'weaken except' does not have to do so necessarily. Even if it does not have any impact the answer is perfectly fine.

Hope its clear!

I am still not able to understand why D is not the answer...since the natural inhabitat has not shrunk it means the ozone layer is not affecting the amphibians....thus weakening our conclusion and so it should be the answer

Answer D says the natural habitat has not become smaller over the past century --> this implies that this is not an alternate cause for the decline in the numbers of the amphibians hence it can imply that the actual cause for declining numbers is in fact the depletion in the ozone.

This is one of the ways of eliminating an answer choice that is eliminating an alternate cause(here shrinkage of habitat) implying that the stated cause(the depletion of ozone) is in fact the only cause of the effect(decline in amphibian numbers)

Hope this helps!!

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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10 Sep 2014, 13:52
I have a question about option C.
It seems as if option C may also weaken the argument.
If there has been significant reduction in the ozone especially where amphibians are living, maybe it's not that the ozone is affecting the amphibians? Maybe it's the amphibians affecting the ozone? perhaps they release some kind of gas that depletes the ozone?
Does anyone see it that way?

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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21 Oct 2015, 12:41
How about option E ? It just says that the amphibian population is decreasing ? Okay. So what is the reason behind the decline ? It can be ozone or it cannot be ozone.

How have you guys eliminated E?

manishkhare - Can you explain A,D and E here.

Thanks

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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24 Nov 2015, 01:40
So, the best response we get so far is:the answer choice A fails to weaken after making it opposite. So, A can't strengthen the causation.
Since negation technique is time-consuming , I have an alternative way to prove A is the answer, though my way is skeptical.
We know that answer choices allow new information to be true. so, only the stimulas (more specifically, the conclusion)here deserves to be challanged. The answer choice A is nothing new desrving attention to challenge or affect the conclusion. Look at the third sentence of the stimulas. The answer choice A just adds 'only' here, otherwose restates what already given to stimulas and adding 'only' is just makes more clear the third statement/premise, but infact, nothing noteworthy to affect the ultimate conclusion. Assume, the sentence of the option A is added to the main syimulas, still, the main point/conclusion becomes unaffected.
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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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26 Nov 2015, 18:08
Steinbeck wrote:
How about option E ? It just says that the amphibian population is decreasing ? Okay. So what is the reason behind the decline ? It can be ozone or it cannot be ozone.

How have you guys eliminated E?

manishkhare - Can you explain A,D and E here.

Thanks

E -> you cannot choose this one because in the text says: "the earth’s ozone layer has been continuously depleted throughout the last 50 years"

D-> Negate this one.
If the natural habitat is smaller than before, then we would have less place for the amphibians to place the eggs. Therefore we would reduce the number of the frogs because of the space. If the space is not reduced then the main cause of the reduction of the species is because of the UV.

A-> It's not because it doesn't weaken, that it is not the correct.
Remember you are being asked about what is the choice that DOESNT strengthen the argument.
Therefore, this is the correct choice.

Remember one more thing, in question that says EXCEPT, the best possible way is to solve it through elimination.

I hope its clear.

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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17 Feb 2016, 04:10

I letter A: suppose that Z-ray do harm the amphibian. Also, the Z-ray passes through the ozone layer. So, if this is true then the conclusion does not hold (the reason for the declining is not the depletion of the ozone layer but the Z-ray). Now letter A guarantees that the only ray tha harm the amphibian is the UVB and the UVB is blocked by the ozone layer. This makes A a strengthener.

Many Thanks.

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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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17 Feb 2016, 07:52
metallicafan wrote:
Amphibian populations are declining in numbers worldwide. Not coincidentally, the earth’s ozone layer has been continuously depleted throughout the last 50 years. Atmospheric ozone blocks UV-B, a type of ultraviolet radiation that is continuously produced by the sun, and which can damage genes. Because amphibians lack hair, hide, or feathers to shield them, they are particularly vulnerable to UV-B radiation. In addition, their gelatinous eggs lack the protection of leathery or hard shells. Thus, the primary cause of the declining amphibian population is the depletion of the ozone layer.

Each of the following, if true, would strengthen the argument EXCEPT:

(A) Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes.
(B) Amphibian populations are declining far more rapidly than are the populations of nonamphibian species whose tissues and eggs have more natural protection from V-B.
(C) Atmospheric ozone has been significantly depleted above all the areas of the world in which amphibian populations are declining.
(D) The natural habitat of amphibians has not become smaller over the past century.
(E) Amphibian populations have declined continuously for the last 50 years.

Respoding to a PM..

Hi,

the para can be rephrased as:-
Quote:
the amphibians have declined in last 50 years. The ozone layer blocks the UV-B rays, which can damage genes. there fore the primary cause of the declining amphibian population is the depletion of the ozone layer.

we have to strengthen it...

lets see the choices..
(A) Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes.
We already know that UV-B can damage genes.. NOTHING NEW to strengthen..
1) the amphibians have been found to have suffered from damaged genes.
2) ONLY UV-B is capable of damaging genes...Here it is just not speaking of rays being blocked but it makes UV-B the only possibility
SO A strong contender unless we find a worse choice

(B) Amphibian populations are declining far more rapidly than are the populations of nonamphibian species whose tissues and eggs have more natural protection from UV-B.
This gives us reason to believe that UV-B is responsible-- a sureshot strengthener

(C) Atmospheric ozone has been significantly depleted above all the areas of the world in which amphibian populations are declining.
Here again, it is correlating decline to ozone deplition--surely a strengthener

(D) The natural habitat of amphibians has not become smaller over the past century.
For a moment, one can be inclined to it.. But, this eliminates a possibility/ reason for this decline-- so in a way strengthens by removing a contender for the decline

(E) Amphibian populations have declined continuously for the last 50 years.
relating the period of decline with the period of ozone deplition, it strengthens the conclusion..

Only A seems to be doing nothing, apart from repeating something which is already known..

Hope it helps..
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Re: Amphibian populations are declining in numbers worldwide. [#permalink]

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14 Nov 2016, 16:56
chetan2u wrote:
metallicafan wrote:
Amphibian populations are declining in numbers worldwide. Not coincidentally, the earth’s ozone layer has been continuously depleted throughout the last 50 years. Atmospheric ozone blocks UV-B, a type of ultraviolet radiation that is continuously produced by the sun, and which can damage genes. Because amphibians lack hair, hide, or feathers to shield them, they are particularly vulnerable to UV-B radiation. In addition, their gelatinous eggs lack the protection of leathery or hard shells. Thus, the primary cause of the declining amphibian population is the depletion of the ozone layer.

Each of the following, if true, would strengthen the argument EXCEPT:

(A) Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes.
(B) Amphibian populations are declining far more rapidly than are the populations of nonamphibian species whose tissues and eggs have more natural protection from V-B.
(C) Atmospheric ozone has been significantly depleted above all the areas of the world in which amphibian populations are declining.
(D) The natural habitat of amphibians has not become smaller over the past century.
(E) Amphibian populations have declined continuously for the last 50 years.

Respoding to a PM..

Hi,

the para can be rephrased as:-
Quote:
the amphibians have declined in last 50 years. The ozone layer blocks the UV-B rays, which can damage genes. there fore the primary cause of the declining amphibian population is the depletion of the ozone layer.

we have to strengthen it...

lets see the choices..
(A) Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes.
We already know that UV-B can damage genes.. NOTHING NEW to strengthen..
1) the amphibians have been found to have suffered from damaged genes.
2) ONLY UV-B is capable of damaging genes...Here it is just not speaking of rays being blocked but it makes UV-B the only possibility
SO A strong contender unless we find a worse choice

(B) Amphibian populations are declining far more rapidly than are the populations of nonamphibian species whose tissues and eggs have more natural protection from UV-B.
This gives us reason to believe that UV-B is responsible-- a sureshot strengthener

(C) Atmospheric ozone has been significantly depleted above all the areas of the world in which amphibian populations are declining.
Here again, it is correlating decline to ozone deplition--surely a strengthener

(D) The natural habitat of amphibians has not become smaller over the past century.
For a moment, one can be inclined to it.. But, this eliminates a possibility/ reason for this decline-- so in a way strengthens by removing a contender for the decline

(E) Amphibian populations have declined continuously for the last 50 years.
relating the period of decline with the period of ozone deplition, it strengthens the conclusion..

Only A seems to be doing nothing, apart from repeating something which is already known..

Hope it helps..

You are right. However, with the same reasoning as D you could eliminate choice A: It eliminates an alternate cause for the decline (other types of radiation).
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Re: Amphibian populations are declining in numbers worldwide.   [#permalink] 14 Nov 2016, 16:56

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