本帖最后由 maybemore 于 2014-7-9 22:51 编辑 |
Arctic deer live on islands in Canada's arctic regions. They search for food by moving over ice from island to island during the course of the year. Their habitat is limited to areas warm enough to sustain the plants on which they feed and cold enough, at least some of the year, for the ice to cover the sea separating the islands, allowing the deer to travel over it. Unfortunately, according to reports from local hunters, the deer populations are declining. Since these reports coincide with recent global warming trends that have caused the sea ice to melt, we can conclude that the purported decline in deer populations is the result of the deer's being unable to follow their age-old migration patterns across the frozen sea.
Write a response in which you discuss what specific evidence is needed to evaluate the argument and explain how the evidence would weaken or strengthen the argument.
The author concludes that the disability of the deer's age-old migration patterns across the frozen sea leads to the decline in deer populations. To support this conclusion, the author alleges that the information of decline in deer's population came from some local hunters. In addition, the author asserted that the decline conforms with the sea ice's meltion, which hinders the migration, caused by global warming. The argument is unwarranted in several aspects.
First and foremost, the argument shows a flaw of limited sample. The author assumes the decline of deer's population based on some local hunters. However, how many hunters hasn't been mentioned. If only two or there hunters live in the same area, the reports are hardly sufficient to establish a general conclusion. It is absolutly possible that the number of deer found by hunters decreased but the whole population does not. Perhaps the deer move to another colony out of the region which the hunters usually come to. Or even further it is entirely possible that the decline of deer's population is due to undue hunting. And the hunters were afraid of be accused by the administrations, so they told a lie. With such limited evidence, it is fallacious to say that the deer's population are declining.
Additionally, even the population of deer really is declining, there is no evidence that it is caused by the disability of migration across the frozen sea. "Lacking proof is no proof". Perhaps the decline is due to reduced food recently for the deer. Or the deer's enemy is imported intentionally or unintentionally, which limited the deer's population. And still no evidence shows that the deer's population would decrease without their age-old migration. The author's failure to investigate or even consider the extra possible explanations for the decline of deer's population renders the conclusion based on it unconvincible.
In general, the author draws the conclusion unconvincible as it stands. To stengthen it, the author should assure the truth and effectiveness of the deer's population, namely is declining or not. And further the correlation between the deer's population and the age-old migration across the frozen sea should be delved.