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Amphibian populations are declining in numbers worldwide.

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Amphibian populations are declining in numbers worldwide. [#permalink]  02 Sep 2004, 03:00
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Amphibian populations are declining in numbers worldwide. Not coincidentally, the earthâ€™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: CR39 [#permalink]  02 Sep 2004, 04:08
chunjuwu wrote:
Amphibian populations are declining in numbers worldwide. Not coincidentally, the earthâ€™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.

I believe it's A

B shows that UV-B is indeed the factor - those who have protection from UV-B are doing better than those who do not

C establishes a correlation by territory between the depletion of the ozone layer and the decline in amphibian population - those who leave in dangerous zones suffer more than those who do not

D rules out an alternative reason why amphibian population could decline

E establishes a correlation by time between the depletion of the ozone layer and the decline in amphibian population - the decline began at the same time as the depletion

A is rather neutral for the argument
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cR39 [#permalink]  02 Sep 2004, 04:13
Yes you are right. Thinking again, I tend to agree with A.
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Agree with A although D was a good catch.
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I pick D though I see no reason to dismiss A.
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I forgot about the 50 years in the passage and so choose E as my answer. I think it should be A.
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bigtooth81 wrote:
I pick D though I see no reason to dismiss A.

If amphibians' natural habitat shrunk, then the decline in their number could be attributed to that particular reason instead of the UVB. Since their natural habitat's size remained intact, it strengthens the argument that some other reason, possibly UVB, must be the cause of amphibians' extinction
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My answer is D. The reason is as under stated.
Conclusion: Ambhibian population is declining due to Decrease in Ozone Layer
Evidence/Support: UV rays damage the genes, Ozone blocks UV rays
Evidence/Support: Ambhibian lack hair and other covering on their body and eggs and therefore more prone to UV rays.

Now
(A) Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes.
....damage genes and therefore decline in polulation. It strenghtens

(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.
....By 2nd evidence strengthens

(C) Atmospheric ozone has been significantly depleted above all the areas of the world in which amphibian populations are declining.
.... strenghtens

(D) The natural habitat of amphibians has not become smaller over the past century.
... This provides nothing to the conclusion that
Ambhibian population is declining due to Decrease in Ozone Layer

(E) Amphibian populations have declined continuously for the last 50 years.
...Ozone has been depleting for last 50 years therefore strenghtens.

Hence D
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(A) Of the various types of radiation blocked by atmospheric ozone,
UV-B is the only type that can damage genes.
- If that is the case, all speicies would be affected.

(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.
- Strengthens the claim UV-B affects amphibians more than nonamphibian species

(C) Atmospheric ozone has been significantly depleted above all the
areas of the world in which amphibian populations are declining.
- If the ozone layer is more deleted above areas where amphibian populatio is declining, then UV-B may be killing them

(D) The natural habitat of amphibians has not become smaller over the
past century.
- then they are not driven. Something else is causing a decline. Might be UV-B, migth be increase in population of their natural predators.

(E) Amphibian populations have declined continuously for the last
50 years.
- same timeline as ozone depletion
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i get how b, c, d, e strenghten but can someone please explain why A is nuetral or does not strengthen. to me it looks good as it says uvb is bad
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(A) Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes.

A is not very good as the radiation could be equally damaging to all species.
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Thank you, all

As ywilfred said, the OA is (D).

D is the least strengthened answer.

In choice A, can we said that there were indeed a radition called UV-B which had been blocked by atmospheric ozone and now it endangered the amphibilian because of the depletion of the ozone layer?

Last edited by chunjuwu on 04 Sep 2004, 08:36, edited 1 time in total.
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Nice catch ywilfred!
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chunjuwu, are you sure the OA is D?

My GMAT material says that the OA is A.

The reason is exaplained by OlegC and Pall.
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Amphibian populations are declining in numbers worldwide. Not coincidentally, the earthâ€™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.

A strengthens the argument becasue it establishes the point that is UV-B that causes the depletion and not any other chemicals otherwise blocked by the atmospheric ozone.

D is the odd one out and it shd be the answer.
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