托福听力材料(Word版本下载)

智课网TOEFL备考资料 托福听力材料（Word版本下载）     摘要： 托福听力材料（Word版本下载）！听力需要考生们备考的时候多去听，有一些单词的发音可能不仔细听会听不出来。大家可以在复习的时候多找一些材料去听，练习多了自然就会很熟练了。文中的一些词汇大家可以反复听几次，下次再去听的时候就会听得很清楚了。一起来看看这篇材料。         小编为同学们介绍 托福 听力材料。听力需要考生们备考的时候多去听，有一些单词的发音可能不仔细听会听不出来。大家可以在复习的时候多找一些材料去听，练习多了自然就会很熟练了。文中的一些词汇大家可以反复听几次，下次再去听的时候就会听得很清楚了。一起来看看这篇材料。         扫描下方二维码获得 托福听力 材料（Word版本下载）                 生词摘录：         1. shrub: n. 灌木         2. resin: n. 树脂         3. beetle: n. 甲壳虫         4. vein: n. 静脉         5. neutralize: v. 中和         6. alter: v. 改变         This morning I want to tell you about a recent scientific discovery dealing with the relationship between plants and animals. This is about a desert shrub whose leaves can shoot a stream of poisonous resin a distance of six feet. You think it would be safe from all attacks by insects? But a recent study has found one insect, a beetle that can chew its way past the plant's defense system by cutting the main vein that delivers the poison to the leaves. This vein cutting is just one method the beetles used to prepare a safe meal. Another is by cutting a path all the way across the leaves to hold the flow of chemicals. Then they simply eat between the veins of poison. In the past, scientists who studied insect adaptation to plant defenses have focused on chemical responses. That is, how the insects can neutralize or alter the poisonous substances plants produce. What's unique about this chewing strategy is that the beetle is actually exhibiting a behavioral response to the plant's defenses rather than the more common chemical response. It is only after a beetle's survived several encounters with the plant's resin that it learns how to avoid the poison: by chewing through the resin transporting veins on the next leaf it eats. And thus gives itself a safe meal. However, it can take a beetle an hour and a half of careful vein cutting to prepare a small leaf that takes it only a few minutes to eat. So, though the method is effective, it's not very efficient.                 相关字搜索： 托福听力材料