Definitely, a victory 小组第5次作业 argument207 By6号骰子

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207. 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.

In this argument, the arguer claims that the increase in the amount of ultraviolet radiation that reaches the surface of the Earth will cause the population declines in animal species. To justify this claim, the arguer provides the evidence that the population of a species of salamander lays its eggs in mountain lakes has declined while the Earth' ozone layer get thinner so that allow more ultraviolet radiation reaches the Earth. A major assumption underlying this argument is that the ultraviolet radiation has damaged the salamander eggs and prevents them from hatching. This line of reasoning is flaw in several aspects.

In the first place, the speaker assert that population of salamander has declined by investigating one species of salamander. It could not exclude any evidence that population of other species of salamander have not declined or even has increased. Also at the later part of argument, speaker subjectively assumes that other species would decline because of same reason of salamander’s decreasing. By ignoring the diversity which exists pervasively in all species, the speaker tends to taking part for the whole. However, even same environment could effect dramatically variously on different species, besides, the amount of ultraviolet might be distributed discrepantly in different geographical areas.

In the second place, the speaker assumes that the ultraviolet radiation leads to salamanders’ declination. Nevertheless, there is no guarantee that the increasing ultraviolet radiation and decreasing population of salamander are cause and effect, even though these two are correlated. It is quite possible that other events, such as air pollution, global warming, and unlimited hunting happen coincidently and then arouse damage to salamanders. To reach the cited conclusion, the speaker must take these alternatives in consideration.

The last but not the least, even if the speaker could proof that ultraviolet is harmful to other species as it is to salamanders, and also could exclude any other possibilities to cause the decline in population, it is still reasonable to doubt that what the arguer assumes will not happen, namely, ultraviolet might not cause the decline in population. For that although mutations and damages may occur by exposing under the ultraviolet, the creatures may not die until these changes are accumulated in some degree.

To sun up, the speaker’s argument mentioned above is not based on sound reasoning and gives no entire consideration, only by grasping a few phenomenon and by relying on inconvincible reducing, the claim is unpersuasive. In order to draw a better conclusion, the speaker should investigate more species in larger scale, also the correlated data is not enough, and he also needs concrete mechanism of ultraviolet-hurt in order to conceal the relationship between population decline and increasing amount of ultraviolet radiation.