英語(yǔ)聽(tīng)力文摘 駱駝

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駱駝,被稱做為"沙漠之舟",它能夠忍耐干燥酷熱的環(huán)境,并且可以在水源極其缺乏的浩瀚沙漠里長(zhǎng)途跋涉,是人們沙漠之旅中不可缺少的伙伴.那么,人們是不是真的了解駱駝呢?曾經(jīng)有兩位美國(guó)科學(xué)家，在非洲的撒哈拉大沙漠對(duì)駱駝進(jìn)行了一次耐旱的“殘忍”實(shí)驗(yàn)。他們把駱駝拴在烈日下整整曬了8天，不給它一口水喝，這只駱駝體重減少了100多千克，肌肉萎縮，筋骨裸露。但令人驚訝的是，它很快就復(fù)原了。關(guān)于駱駝耐旱的秘密,至今沒(méi)有一個(gè)令人滿意的說(shuō)法.

A camel can travel hundreds of miles, over several days, without stopping to drink.

On today's Moment of Science, we’ll learn how camels survive the dry desert.

Let’s start with the hump. Contrary to what you might have heard, camels do not store extra water here. The hump stores fat, providing energy for their long, desert trek. This fat, however, can help keep a camel from getting thirsty. As the fat is burned, water is produced as one of the byproducts. This extra water enters the camel’s bloodstream to add to its water supply.

Camels conserve water by not sweating as much as we do. A camel’s metabolism lowers at night, making its body temperature much lower than a human’s. Because we sweat to cool ourselves off, starting with a lower body temperature means less need to sweat. Camels are also covered with heavy fur which keeps the daytime heat out. Because it’s so good at keeping its cool, a camel can travel a long way without sweating very much.

Camels are also good at maintaining their blood volume. Once we humans lose about twelve percent of our body’s water, our blood becomes too thick to work properly. A camel’s blood, however, stays more or less consistent, allowing the camel to lose up to twenty-five percent of its weight by dehydration.

Another thing that helps a camel conserve water is its nasal passages. When we exhale, we loose a lot of water vapor, as any fogged up car window will prove. Camels have extra dry nasal passages which actually recondense the water out of each breath, allowing much less to escape.

As you can see, there is no single explanation for a camel’s desert survival abilities. Instead, a camel draws on a whole range of adaptations.

譯文：

駱駝可以行走數(shù)百英里，并在幾天之內(nèi)也不用喝水。

在今天的科學(xué)一刻中，我們將會(huì)學(xué)習(xí)駱駝是怎樣在干燥的沙漠中生存的。

我們先從駝峰說(shuō)起，和你所聽(tīng)說(shuō)的不一樣的是，駱駝并沒(méi)有儲(chǔ)存多余的水在這里。駝峰積聚著脂肪，為它們長(zhǎng)距離的沙漠旅行提供能量。然而就是這些脂肪，可以幫助駱駝止渴。水就是這些脂肪燃燒所產(chǎn)生的副產(chǎn)物之一。這些額外的水進(jìn)入駱駝的血液，增加其水分的供應(yīng)。

駱駝不像我們那樣出汗，這樣也可以儲(chǔ)存水分。駱駝的新陳代謝到晚上就會(huì)降低，讓它的體溫低于人類。出汗可以冷卻我們自己，因此如果體溫較低的話，對(duì)汗水的需求也會(huì)比較少。駱駝同樣覆蓋著厚重的皮毛，這些皮毛可以防止白天的熱量進(jìn)入體內(nèi)。正因?yàn)轳橊勅绱松瞄L(zhǎng)保持其身體的冷卻，所以它可以走很長(zhǎng)時(shí)間，卻不會(huì)流很多汗。

駱駝同樣也很擅長(zhǎng)保持它們的血容量。我們?nèi)祟愐坏┝魇Я松眢w百分之十二的水分，血液就會(huì)變得太濃稠以至于不能正常工作?？墒邱橊劦难?，總是可以堅(jiān)持到讓其脫水到其重量的百分之二十五。

另一個(gè)有助于駱駝儲(chǔ)存水的東西就是鼻腔。當(dāng)我們呼氣的時(shí)候，我們會(huì)流失許多水蒸汽，被霧氣模糊的車窗可以證明這一點(diǎn)。駱駝?dòng)蓄~外的干燥鼻腔，可以凝聚每次呼吸的水分，讓水分的蒸發(fā)的變少。

就如你所見(jiàn)，沒(méi)有關(guān)于駱駝沙漠生存能力的單一解釋。相反地，駱駝?dòng)幸幌盗械倪m應(yīng)能力。