2016年GRE寫作范文解析：物種減少
Topic
The following is a letter to the editor of an environmental magazine："The decline in the numbers of amphibians worldwide clearly indicates the global pollution of water and air. Two studies of amphibians in Yosemite National Park in California confirm my conclusion. In 1915 there were seven species of amphibians in the park, and there were abundant numbers of each species. However, in 1992 there were only four species of amphibians observed in the park, and the numbers of each species were drastically reduced. The decline in Yosemite has been blamed on the introduction of trout into the park's waters, which began in 1920 (trout are known to eat amphibian eggs). But the introduction of trout cannot be the real reason for the Yosemite decline because it does not explain the worldwide decline."
Sample Essay
In this argument, the writer of the letter concludes that global pollution of water and air has caused a decline in the number of amphibians worldwide. To support his or her conclusion, the writer cites the results of two studies, seventy-five years apart, that purportedly show that the number of amphibians in one park in California, Yosemite National Park, have drastically declined. Additionally, the writer casts aside a given reason for the decline, stating that the introduction of trout to the park (who are known to eat amphibian eggs) does not explain the worldwide decline in the number of amphibians. This argument defies simple logic and suffers from several critical fallacies.
First of all, the argument is based on only two studies in one specific part of the world, Yosemite National Park in California. It is impossible to pinpoint a worldwide theory for the decline of amphibians based on any number of studies in only one specific location in the world - the specific varieties of amphibians, geographical conditions and other location specific variables prohibit such a sweeping generalization. One very specific location cannot be used as a model for all other locations, even within one particular country, let alone the entire world. The writer provides no evidenced whatsoever that links the Yosemite study with any purported effects anywhere else in the global environment.
Secondly, the two separate studies were done seventy-five years apart. There is no evidence that the two studies were conducted in a similar manner over the same duration of time or even over the same exact areas of Yosemite National Park, or that the exact same study methods were used. For example, perhaps the first study lasted over an entire year and was conducted by twenty-five experts in amphibious biology, resulting in the finding of seven species of amphibians in abundant numbers. By contrast, perhaps the second study was conducted over a period of one week by a lone high school student as a school science project. The writer offers no basis on which to compare the two studies, leaving it open as to whether the two are truly comparable in their breadth, scope and expertise.
Finally, the writer notes that the decline in the amphibian population has been blamed on the introduction of trout into the park's waters in 1920, but then dismisses that argument on the purely specious basis that it does not explain the worldwide decline. This part of the argument blithely dismisses the very relevant fact that trout are known to eat amphibian eggs. This attempt to "prove a negative" is the last resort of those in search of some vain attempt to prove the truth of the matter that they are asserting. It is basically impossible to "prove a negative"; this is an attempt to shift the burden of proof back on to the nonbelievers of the argument. The global environmental situation and that of Yosemite National Park are not perfectly correlated, and the fact that the trout may very well be responsible for the decline cannot simply be dismissed without further proof.
In summary, the writer fails to establish any causal relationship between global air and water pollution and the decline of amphibious life worldwide. The evidence presented is extremely weak at best and narrowly focuses on one tiny area of the globe, as well as putting forward as proof two studies about which almost nothing is known. For a stronger argument, the writer would need to directly put forth evidence associating air and water pollution with not only the decline at Yosemite but also throughout other areas of the world.
下述文字摘自一封致某環(huán)保雜志編輯的信函："全球兩棲動物數(shù)量的減少明顯標志著全球性水與大氣的污染。對加利福尼亞州約塞米蒂國家公園內(nèi)兩棲動物所作的兩項研究可證實我的這一結(jié)論。1915年公園內(nèi)有七個物種的兩棲動物，每一物種都擁有豐富的種群數(shù)量。然而，1992年，在公園內(nèi)所能觀察到的兩棲動物物種僅為四類，且每一物種的種群數(shù)量已驟然下降。約塞米蒂公園動物數(shù)量減少被歸咎于始于1920年的將鮭魚引入公園水域的做法(眾所周知，鮭魚喜食兩棲動物所產(chǎn)的卵)。但鮭魚的引入不可能成為約塞米蒂公園動物數(shù)量減少的真正原因，因為它無法來解釋全球范圍內(nèi)的動物數(shù)量減少。"
在本項論述中，信函作者的結(jié)論是，全球性水與大氣污染已致使世界范圍內(nèi)兩棲動物的數(shù)量減少。為了支持其論點，作者援引了兩份時隔75年之久的研究結(jié)果，這兩份結(jié)果據(jù)稱可證明加利福尼亞州某一公園――即約塞米蒂國家公園――內(nèi)兩棲動物的數(shù)量銳減。此外，該作者撇開了動物數(shù)量減少的一個已知原因，陳述道，將鮭魚引入公園(據(jù)稱，鮭魚喜食兩棲動物所產(chǎn)的卵)這一做法不足以解釋世界范圍內(nèi)兩棲動物數(shù)量上的減少。這一論點有悖于簡單的邏輯，犯有一系列關(guān)鍵性的邏輯謬誤。
首先，該論點所依據(jù)的僅僅是世界上某一特定地點――即加利福尼亞州約塞米蒂國家公園――內(nèi)的兩份研究。圍繞著兩棲動物數(shù)量減少這一問題，如果僅以世界上一個特定的地點為樣品，再多數(shù)量的研究也無法得出一種精確的、適用于全世界的理論。兩棲動物的具體種類、地理狀況以及其他因地點而特異的變數(shù)均不允許我們作出如此一概而論的總括。一個非常具體的地點不能用作一個代表所有其他地點的模型，即使在一個特定的國家內(nèi)也不行，更不用說在整個世界范圍內(nèi)了。信函作者沒有提供任何證據(jù)將約塞米蒂公園的研究與全球環(huán)境中任何其他一處地方的任何所宣稱的效果聯(lián)系起來。 其次，所提及的那兩項互為獨立的研究時隔75年之久。沒有證據(jù)可證明這兩項研究是在相同的時間跨度內(nèi)以相似的方式進行的，或是在約塞米蒂公園完全相同的地點進行的，或所使用的研究方法絕然相同。
例如，第一項研究可能持續(xù)了整整一年之久，且是由兩棲動物生物學領(lǐng)域的二十五位專家共同進行的。結(jié)果是發(fā)現(xiàn)了七大種類數(shù)目眾多的兩棲動物。相反，第二項研究可能是一位高中生孤身一人所做的學校的一個科學課題，僅為期一個星期。信函作者沒有提供將此兩項研究進行比較的基礎(chǔ)，從而使兩項研究在其廣度、范圍以及專業(yè)水準方面的可比性不得而知。 最后，信函作者指出，兩棲動物種群數(shù)量的減少，已被人歸咎于1920年將鮭魚引入公園水域這一做法，但緊接著又以該論據(jù)無法解釋世界范圍內(nèi)動物數(shù)量減少這一似是而非的依據(jù)將該論據(jù)予以否認。信函作者論述中的這一部分漫不經(jīng)心地將一個極為相關(guān)的事實棄置不顧，即眾所周知，鮭魚喜食兩棲動物所產(chǎn)的卵。這種"prove a negative "的嘗試往往是這樣一類人所慣用的最后伎倆，他們竭力尋找某種徒勞的嘗試，力圖去證明他們所宣稱的事物的真理。從根本上講，"prove a negative"是不可能的。這樣一種做法是試圖將論證的負擔重新轉(zhuǎn)嫁給不相信該論據(jù)的人。全球的環(huán)境情形與約塞米蒂公園的情形并不絕然對應(yīng)。鮭魚極有可能造成了兩棲動物數(shù)量減少這一事實在缺乏進一步證據(jù)的情況下是斷不能輕易予以否認的。
概括而言，信函作者沒能在全球空氣和水污染與世界范圍內(nèi)兩棲生命數(shù)量減少之間建立起任何因果關(guān)系。該作者所拿出的證據(jù)充其量也是極為蒼白無力的，狹隘地將焦點集中在世界的一片極小的區(qū)域上，作為證據(jù)而援引的兩項研究幾乎不能說明任何問題。欲使其論點更具力度，信函作者尚需擺出直接的證據(jù)，將水和空氣污染不僅僅與約塞米蒂公園的兩棲動物數(shù)量減少聯(lián)系起來，而且也與世界其他地方的動物數(shù)量減少聯(lián)系起來。
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