概括：內(nèi)容選自老托福聽力，是練習(xí)托福聽力的絕佳材料。


啊，妹子，來得好，你看，我有姿勢(shì)我自豪...其實(shí)我不會(huì)彈，看不出來吧！
If you liked the colorful animals we just saw, you're going to love these next animals - frogs. You might not normally think of frogs as being colorful, but these frogs definitely are. They are the dart-poison frogs of Central and South America. Look at their striking colors - often yellow with black stripes or deep blue with black spots. Beyond being nice to look at, these markings have a purpose. They warn predators that these frogs are poisonous. When threatened, these frogs secrete a substance through their skin that would easily kill whatever animal might try to eat them. Their bright colors communicate this, and so most animals tend not to hunt them. Now, speaking of hunting, for centuries these frogs were sought after by hunters. As you might think, the hunters didn't want to eat the frogs, but rather, they captured them for their poison. They would add the poison to the tips of their hunting arrows, of course, nowadays most hunters use guns. These days dart-poison frogs are of less interest to hunters than to medical researchers. Researchers believe that they can make a new heart medicine from the poison, because it acts as a stimulant on the body's nervous system. Researchers think they could use it to stimulate a weak heart. There is, however, a problem with doing research on these frogs. Those that are caught in the wild will produce their poison until they die. However, those that are born in captivity, like the ones you see here, will not produce any poison at all.
如果你喜歡我們之前看過的多彩的動(dòng)物，你肯定會(huì)喜歡下一種動(dòng)物—青蛙。正常情況下，你也許不認(rèn)為青蛙是彩色的，但很明顯，這種青蛙是彩色的。它們是生活在美國(guó)中南部的箭毒蛙?？此麄兠黠@的色—經(jīng)常是黃黑的條紋或者是深藍(lán)的中帶著黑色的斑點(diǎn)。 突出的膚色除了好看，還有一定的用途。這種顏色可以警告獵食者：“我是有毒的！”當(dāng)受到威脅時(shí)，這種青蛙分泌一種有毒物質(zhì)，這種毒物可以殺死任何想吃掉它們的動(dòng)物。箭毒蛙通過它們的警戒色來傳遞這種信息，所以，大多數(shù)動(dòng)物不喜歡捕獵箭毒蛙。 談到捕獵，現(xiàn)在，近一個(gè)世紀(jì)以來，這種箭毒蛙一直在被捕獵。很明顯，捕獵者不是為了吃箭毒蛙，而是為了他們的毒物。捕獵者把毒物涂在捕獵用的弓箭頭上。當(dāng)然，現(xiàn)在，大多數(shù)獵人用槍。 最近，醫(yī)學(xué)研究者比獵人對(duì)箭毒蛙更感興趣。他們認(rèn)為箭毒蛙的毒液有刺激神經(jīng)系統(tǒng)的作用，所以可以用來制作藥物來刺激微弱的心臟。 然而，研究過程中也發(fā)現(xiàn)了問題。在野外補(bǔ)到的箭毒蛙會(huì)持續(xù)分泌毒物直到死亡。然而，被捕獵后出生的箭毒蛙壓根不產(chǎn)生任何毒物。 ——譯文來自: fanrong1985