2. 外语
  3. Arctic deer live on islands in Canada’s arctic regions. They search for food by moving over ice from island to island during the

Arctic deer live on islands in Canada’s arctic regions. They search for food by moving over ice from island to island during the

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问题 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.
选项
答案 In this argument, the author cites reports from local hunters as evidence for the decline of the arctic deer populations, and subsequently attributes this decline to global warming, which allegedly makes deer unable to follow their migration patterns across the frozen sea. Although the argument seems plausible at first glance, a close scrutiny will reveal that additional evidence is necessary for an effective evaluation of its validity. Firstly, the author asserts a decrease in the deer populations merely based on reports from local hunters. However, such reports may not serve as a convincing indicator, since the deer might have intentionally avoided direct contact with hunters in order to survive the hunting. Therefore, more persuasive evidence must be presented for a better evaluation of the populations. For example, a scientific study surveying the entire area could offer much stronger evidence for the change in deer populations. If the results of the study show that the overall populations are indeed on the decline, it will be justifiable for the argument to further discuss the reasons for it. On the other hand, if the results evidence constant or even increasing populations, the discussion of reasons for the decline in populations in the argument will be rendered groundless. Secondly, specific evidence regarding the change of temperature in the arctic regions is also needed to evaluate the author’s reference of global warming. This is because the earth’s climate is an intricate system and the trend of global warming does not necessarily result in an increase in temperature and cause sea ice to melt in the local arctic regions of interest. If local temperature data illustrate a non-varying or even colder climate, the adoption of global warming to account for phenomena in these regions will be highly suspicious. On the contrary, local temperatures that manifest a climate change consistent with the general trend of global warming will help strengthen this point of reasoning in the argument. Furthermore, even if we corroborate the decline in deer populations and acknowledge a warmer climate in the arctic regions, further evidence is still necessary for an evaluation of the author’s causal association of the decline in deer populations with the increased local temperatures. As a matter of fact, the populations of deer depend on more factors than climate alone, such as the quantity of their predators and epidemics. Consequently, it is of great significance to examine all the possible causes for population changes, and find out evidence for the roles they are playing. If evidence demonstrates that reasons other than increased temperatures are primarily responsible for the observed population decline, the purported link between this decline and climate change will be greatly weakened. Nevertheless, on condition that evidence is found to be able to testify the negligibility of all the other influences and rule out all the alternative explanations for the population decline, the causal relationship between the decrease and warmer climate, claimed in the argument, will be considerably strengthened. Finally, granted that the deer populations do decline due to increased local temperatures associated with the global warming, concrete evidence still remains desirable to evaluate the author’s assertion that it is via disturbing the deer’s migration patterns that the warmer climate reduces the populations. As mentioned above, the survival of deer relies on numerous factors, many of which are likely to be affected by temperature, and hence evidence from investigation into all these temperature dependent factors has to be obtained. Provided that such evidence reveals, for instance, that the higher temperatures endanger plants the deer mainly feed on and that the population drop is a result of food shortage caused by increased temperatures but not inability to migrate, the conclusion of the argument will prove untenable. Conversely, evidence undoubtedly exhibiting that the warmer climate melts the sea ice and leads to the deer’s failure to follow the old-aged migration pattern and ultimately their massive death will be in strong support of the proposed reason for the drop of deer populations in the argument. To sum up, evidence beyond what has been brought forward by the author is required for a legitimate evaluation of the reasoning and conclusion of the argument. Specifically, detailed and reliable evidence concerning the deer populations, the climate change in the arctic regions, as well as all the factors that are capable of affecting the deer populations, whether temperature dependent or not, will be helpful with evaluating the credibility of the argument. (735 words)
解析     本题围绕着几个独立的线索得出一个总的结论：鹿的数量下降(根据猎人的汇报)是源自于全球变暖导致的海冰减少，进而引起鹿群无法迁徙。其逻辑导图如下所示：
    鹿需要海冰完成迁徙+猎人报告鹿的数量下降+全球变暖导致海冰减少→解释：这是因为鹿无法找到海冰迁徙
    和之前所看到的单线程递进推导不同，本文的题干是纯粹的并联，也即基础的信息之间彼此不相关，因此在论证过程中我们可以各个击破。
    本文第一段我们选择了猎人的报告，这里本质上是一个调查——调查数据能否真实反映客观世界的情况?对于本题来说，就是猎人的感觉是不是客观且真实的?显然这是不一定的，因为猎人的观测本质上是一种主观的感受，可能与客观世界的情况存在偏差(bias)。譬如本文所说的鹿也许变聪明了，刻意躲着猎人，这样即便鹿的总数不变，也会给猎人一种鹿的数量在下降的错觉。因此，我们指出还需要更多的证据来判断鹿的数量是否真的在下降。这里有同学可能会问，为什么我们不把“鹿需要海冰完成迁徙”这句话放在第一段讨论呢?原因在于这一句话本身在此处是背景信息的介绍，而非进行逻辑上的推论，因此在写A娼啪ent的过程中不需要分析其正确与否。
    接下来在确认鹿群数量下降之后，我们可以开始思考其下降的原因。原文给出的理由其实包含两层：第一层是宏观上的全球变暖，第二层是微观上的作用机制——海冰融化之后鹿群无法迁徙。为此，我们也要拆解成两段进行分析，并按照逻辑的演绎先分析是否与全球变暖相关，再分析就算与之相关，具体的机制又有哪些。相信想到这两层的同学肯定会想到，能导致一个种群数量变化的因素太多了，一方面是天敌，一方面是食物。这里我们选择天敌(人类)作为全球变暖之外的另一种可能原因，而把因气候变暖导致的食物短缺当作海冰减少的竞争选项。而这些可能性都是现有的信息无法判断的，我们还需要更多的证据来进行评价。至此，文章的三个论证段就呼之欲出了。
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