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stanford007
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发表于 2007-1-25 18:32:11 |只看该作者 |倒序浏览

TOPIC: ARGUMENT207 - It is known that in recent years, industrial pollution has caused the Earth's ozone layer to thin, allowing an increase in the amount of ultraviolet radiation that reaches the Earth's surface. At the same time, scientists have discovered, the population of a species of salamander that lays its eggs in mountain lakes has declined. Since ultraviolet radiation is known to be damaging to delicate tissues and since salamander eggs have no protective shells, it must be the case that the increase in ultraviolet radiation has damaged many salamander eggs and prevented them from hatching. This process will no doubt cause population declines in other species, just as it has in the salamander species.
WORDS: 310       TIME: 0:30:00       DATE: 2007-1-25

Citing the thinning of Earth's ozone layer and population decrease of salamander, the writer concludes that population declines of all other species are caused by the damage of ozone layer in order to justify the harm of the industrial pollution.  However, the argument relies on a series of unproven evidences and flaw reasoning, and thus the conclusion that it stands on is unconvincing.

To begin with, the writer assumes that the thin ozone layer will let increasing arrival of ultraviolet radiation in the over Earth. Yet we don’t know whether the whole ozone layer is growing thinner. Nor we know the difference of ultraviolet absorption for thin ozone layer from that of chick ozone layers. Without more details, the writer cannot conclude that the thinner ozone layer causes the increase ultraviolet radiation in the whole Earth.

Second, the writer assumes that the population decrease of salamander is due to decline of eggs laid on the mountain lake.  However, it is hard to make such conclusion because salamander likes to lay their eggs on downhill, for example, rather than in mountain lake. Also because the number of eggs decline is due to decrease of salamander population which are poisoned by the usage of pesticides. Therefore, without ruling out these or other causes, the writer cannot make the conclusion convincing.

In addition, nor can the writer justify that that ultraviolet radiation (UR) damaging the many salamander eggs can cause the decline of its population. It is very possibly that the eggs in mountain lake will not be damaged by the ultraviolet radiation because of water. It also perhaps that, though some salamander eggs in mountain lakes are damaged, most eggs in other places still are healthy.  Thus, it is unconvincing that the vulnerability of eggs to the radiation is main cause of the decline of population.

Finally, even though the thin ozone layer causes the decline of salamander population, the writer definitly cannot deduce that population decline of other species is the same cause as salamander by reasoning of a poor analogy.

To summarize, the arguments relies on what amounts to confusing cause-and-effect between the thin ozone layer and salamander population decline, the poor analogy of population decrease of salamander with the decline of all other species, and the incomplete details about relation of the number of egg decrease in a specific place and the whole decline of population. To strengthen the argument, the writer should provide more details, including that thin all the ozone layer is thinning allowing for more ultraviolet radiation through to the earth surface, that the mountain lake is the main place for laying egg, that the hatch rate decline is due to the radiation of ultraviolet, and that other species have the similar habitat and biological characteristic of salamander.