CR:Amphibian populations

[tak2pratik]

Source: Powerscore CR Bible

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.

Please explain why the OA is A. Also,an explanation as to how the other options can be eliminated will prove helpful.

[junaidzaheer]

pratik,
I will take an attempt at answering your question. This is also my first post on MGMAT, so lets hope I can explain it well.

Premise: Ozone is depleting for 50 years. Ozone blocks UV-B which is responsible for gene damage. Also, Amphibian population is declining. Amphibians lack hair, hide etc making them vulnerable to UV.

Conclusion: Ozone depletion caused decline of Amphibian Population

The questions asks for the choice which does NOT strengthen the conclusion. In order to do so, we have to find the option that does not relate to the conclusion

B. says that non-amphibian population which has tissues and eggs are not declining. This means species without tissues will be affected, i.e. Amphibians. This option strengthens out conclusion

C. says Ozone has depleted in all areas where Amphibians are populated. This option is strengthening the link between Ozone depletion and population decline.

D says natural habitat is same, meaning it is not a cause of population decrease. Another straightener

E. says population has declined constantly for 50 years. Ozone has also been depleting for 50 years, which means it is also a strengthener.

A is not tied to the conclusion and says OV-B is the only type that damages the tissues. It does not relate with the conclusion that says depletion of Ozone is causing decline in population. Hence it is our answer.

[tak2pratik]

thank you :).

[tim]

.