2015年2月1日托福综合写作真题及范文：

Reading 阅读

三个理论可以解释 yellow-legged frogs 在过去40年间的大量减少：

1）外来物种的入侵。因为本地没有这种外来生物，所以青蛙没有抵御这种生物入侵的能力，导致大量灭亡；

2）害虫剂的扩散。青蛙的栖息地靠近加州的一个农业非常发达的乡村，为了遏制害虫破坏庄稼而使用了大量的农药和杀虫剂，最终青蛙也受到感染、从而大量灭亡；

3）真菌疾病的传播。因为真菌疾病中携带着一种特殊的化学物质，青蛙对这种物质没有抗体，导致大量灭亡；

Listening 听力

阅读提到的三种理论都存在各自的缺陷：

1）因为当地人喜欢在不合适的时间段钓鱼，所以其实外来物种早就已经通过钓鱼这种方式不存在了；

2）杀虫剂只会通过风或者水流走向低处，但是这个村庄本身在高地，所以杀虫剂不会危害到村庄中的青蛙；

3）研究证明，青蛙本身对于真菌疾病是有抵抗因子的；

Sample answer

The mountain yellow-legged frog population has been undergoing rapid decline over the past 50 years. The reading passage attributes such decline to three possible causes, while the lecture points to the weakness of each cause proposed in the reading.

The first cause is the introduction of the trout in the frog's natural habitat. The trout feeds on tadpoles and therefore reduces the number of frogs. However, the lecture argues that the introduction of the trout took place over 100 years ago, long before the decline of the frog population, which occurred about 40 years ago.

The second cause is pesticide, which is widely used in farming. Remnants of pesticides which contain poisonous chemicals could have drifted to the frog's habitat, causing the decline in frog population. However, the lecture points to an important weakness in this theory because the frogs which inhabit areas in the upper streams of the river have also undergone a decline. Since the pesticides could not travel uphill through the river system, the pesticide theory is clearly flawed.

Another possible cause is fungal disease, which could have infected the frog's skin and led to its death. However, according to the lecture, the yellow-legged mountain frog has the ability to produce chemicals to protect themselves.