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# Amphibian populations are declining in numbers worldwide.

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Amphibian populations are declining in numbers worldwide. [#permalink]  12 Jul 2008, 03:53
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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
UV-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.
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  12 Jul 2008, 04:33
another tough one ...

i'll go with E ....

suppose 50 years back the strength of Ozone layer was 100 unit and every year is going down by 1 unit .... then the polpulation decrease rate should have been less 49 years back (ozone layer = 99) than it ins now (ozone layer = 50)...

E says that the decrease has been continous .... means teher are also other factors ... this does not strength the argument....
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  12 Jul 2008, 04:50
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
UV-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 go with A. E talks about continuity and has no relevance with rates of decline so I guess the argument supporting E is not absolute.
A seems more likely because this does not actually strengthen the argumnet in real sense as the conclusion is depletion of Ozone is the reason for decline irrespective of whether it is onlu UV B or something else.

What is OA?
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  12 Jul 2008, 05:13
A.

Conclusion: The primary cause of the declining amphibian population is the depletion of the ozone layer.
Premise : Atmospheric ozone blocks UV-B, a type of ultraviolet radiation that is continuously produced by the sun, and which can damage genes.

The only additional information in option A is that UV-B ray is the only type that can damage genes. Lets say we did not know this then there are two possibilities
1. there was another ray that affected the amphibian population
2. No other ray affected the amphibian population .
In both the cases the existence of UV-B ray will still affect the amphibian population.
Thus i feel option A does not strengthen the argument.

On the other hand option E does strengthen.
Because lets say the Amphibian populations declined continuously for the last 60 years instead of 50 years. This makes a difference. Because for the extra 10 years that the amphibian population has been declining the ozone layer cannot be the reason(As the passgae says : the earth’s ozone layer has been continuously depleted throughout the last 50 years.)
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  12 Jul 2008, 23:50
OA A
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  05 Aug 2010, 23:08
Some more explanation please:

D) Answer choice D -> What does over the past century mean ? Doesn't it include the last 50 years?

If it includes, then it says the change in ozone layer hasnt affected the amphibian population.

I understand from the conclusion that, the ozone whole is linked to amphibian reduciton and not the UV rays. Therefore it is perfectly fine to say that choice A doesnt add any value to support the argument. But please provide explanations for the answer choice D
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  06 Aug 2010, 04:01
Love this argument. Yes the answer should be A. Because its attributing the cause of X - decline in ambhibian population to Y - ozone depletion. An alternate explanation can weaken the argument.

Ozone depletion is the NOT the primary cause of the decline in amphibian population because -
(A) Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes. ----> This means there is a THIRD factor which is the culprit. Since UV-B are blocked.

B and C strengthen the argument.
(D) The natural habitat of amphibians has not become smaller over the past century. ---> Scope shift.
(E) Amphibian populations have declined continuously for the last 50 years. -----> Strengthen the argument.
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  11 Aug 2010, 08:42
Good one....GO with A
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  11 Aug 2010, 09:59
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Can someone explain how D stregthens the argument?

D..The natural habitat of amphibians has not become smaller over the past century....that means the amphibians is not declining and no ozone layer effecting the population.
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  11 Aug 2010, 11:13
Even I agree with seekmba
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  11 Aug 2010, 15:54
IMO...A
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  12 Aug 2010, 17:47
Agree with A ....

Last edited by Bhuvanamani on 23 Aug 2010, 17:40, edited 1 time in total.
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  12 Aug 2010, 18:55
A it is.
A does not make sense.

The rest all strenghten the argument.
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  12 Aug 2010, 23:03
To me A strengthens the argument.
need more explanation as why OA is a.!
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  18 Aug 2010, 01:49
A IT IS
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  30 Aug 2010, 04:17
IMO D does not strengthen the argument. Could anyone please explain why OA is A as it clearly strengthens the argument? What is the source of the question?
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  30 Aug 2010, 11:39
my first reaction was D as D does not strengthen the conclusion.
Why the OA is A?
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  30 Aug 2010, 17:28
D eliminates another possible explanation for the population decrease, therefore strenghtens the argument. If the habitat got smaller, may be that's the reason why the population got smaller then.
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  01 Sep 2010, 15:49
IMO as well D .
A : UVB is the only rays that damages genes .Depletion of ozone is resulting in UVB not getting blocked (Ozone blocks UVB) and hence affecting the amphibian population .How can this not strengthen the argument .Please explain,
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Re: CR : Amphibian populations are declining in numbers worldwid [#permalink]  02 Sep 2010, 01:18
D as well
Re: CR : Amphibian populations are declining in numbers worldwid   [#permalink] 02 Sep 2010, 01:18
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