Amphibian populations are declining in numbers worldwide. Not coincidentally, the earth's ozone layer has been conti...

Sangwook on December 10, 2014

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Isn't (a) strengthening the argument? I don't understand why (a) fails to strengthen the argument. Thanks,

1 Reply

Melody on December 12, 2014

Okay so this one is a little tricky.

We are told that amphibian populations are declining in numbers worldwide. We also know that throughout the last 50 years, the earth's ozone layer has been continuously depleted. The argument explains that atmospheric ozone blocks UV-B--a type of radiation that is always produced by the sun, which can damage genes. The argument explains that since amphibians and their eggs lack protective covering, they are particularly vulnerable to UV-B radiation. The argument then concludes: "the primary cause of the declining amphibian population is the depletion of the ozone layer."

Answer choice (A) states: "Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes."

Ask yourself, does this help strengthen the argument that the primary cause of the declining amphibian population is the depletion of the ozone layer? No.

We know that the earth's ozone layer has been continuously depleted throughout the last 50 years, and that the ozone blocks UV-B, which can damage genes. But, merely knowing that UV-B is the only radiation that can damage genes doesn't really do anything to our argument that the primary cause of the declining amphibian population is the depletion of the ozone layer. Who cares if there are other harmful types of radiation? Would that not support the fact that the ozone is the primary cause of the declining amphibian population?

Remember, we are not supporting the idea that UV-B radiation is the primary cause of declining amphibian population; rather we are supporting the idea that the depletion of the ozone layer is causing the declining amphibian population.

So, merely knowing that UV-B rays are the only harmful type of radiation does nothing to strengthen the argument. We already knew UV-B rays were harmful. Adding more types of radiation or stating that UV-B rays are the only kind of ray that is harmful does nothing to change the fact that because there are harmful rays (regardless of how many types), the depletion of the ozone is the primary cause of the declining amphibian population.

Don't forget, "not strengthening" does not necessarily mean "weakening." If something does not strengthen, then it can either do nothing or it can weaken.

Hope that clears things up! Please let us know if you have any other questions.