Definitely, a victory 小组第4次作业 Argument207 By3号echo（huohuo0101）

huohuo0101UID: 2760840

207It 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.

提纲：
空气污染物导致臭氧层变薄，因此地表的紫外线辐射增多。作者认为过度的紫外线辐射是火蜥蜴数量减少的原因，因为它破坏了火蜥蜴无保护壳的卵。并且作者推论其它物种的数量也会因为同样原因而减少。
逻辑错误
蜥蜴数量减少是由于过度辐射造成的这个推论有很多漏洞。
1虽然全球臭氧层的平均厚度减少，但是无证据火蜥蜴生存的地区臭氧层变薄
2火蜥蜴数量减少有可能是因为其它原因，比如脆弱的蛋收到了其它东西的侵蚀
就算火蜥蜴数量的减少真的是因为紫外线辐射的增加，对于其它物种也不一定适用

The author believes that over radiation of ultraviolet led by thinning ozone layer causes population of salamander resident in mountain lake area to decline, mainly because ultraviolet damaging the eggs which are without protective shelf. And further predicts that population of other species will also decline due to the same reason. The argument is flawed in several aspects.

First of all, the assumption that ozone layer in the mountain lake area where salamanders’ habitant is located gets thinner is poorly evidenced. Ozone layer thins around the globe, but it may not be the case for a particular area. It’s possible that air pollution there is well controlled so that the pollutant are not dense enough to do harm to the ozone. Or the air pollutant there does not contain certain element such as florin which promotes the ozone layer thinning process.

Second, there is no evidence supporting the conclusion that decline of salamander population is resulted from inability to hatch. The unsolved mystery could be due to emigration, lack of food or sudden climate change. Even if it’s damage of eggs that cause the population to decline, there are alternative reasons to explain except over ultraviolet radiation. For example, the population of species who eat eggs of salamander may be increasing. Without ruling out other possible explanations, the author can not put causal link between the former and the latter.



Even assuming over ultraviolet radiation encroach the eggs thus leads the population to decline, the author can not reasonably infer that other species are as vulnerable as salamander. Perhaps the absence of shell combined with special residence—mountain lake renders salamander vulnerable to ultraviolet. If so, author’s prediction for other species is unsubstantiated.


Finally, the author’s prediction relies on the assumption that ozone-thinning trend will continue advancing in the future. In fact, effective control method against air pollution and self-recovery ability of aerosphere is likely reverse the thinning process. The author can not convince me without accounting for the possibilities.

To sum up, the assertion is based on some unsubstantiated assumptions thus make it unconvincing as it stands. To bolster the assertion, the author has to provide convincing evidence showing that ozone above salamander habitant is thinning, and must rules out other explanations for the population decline. To infer the conclusion to other species, clear evidence that other species are also vulnerable to ultraviolet should be presented and the author need to explain why other species have not experienced the population decline yet. At last, statistics or graphs showing how earth’s ozone layer will develop in the future will make the inference more persuasive.