Camels
骆驼,被称做为"沙漠之舟",它能够忍耐干燥酷热的环境,并且可以在水源极其缺乏的浩瀚沙漠里长途跋涉,是人们沙漠之旅中不可缺少的伙伴.那么,人们是不是真的了解骆驼呢?曾经有两位美国科学家，在非洲的撒哈拉大沙漠对骆驼进行了一次耐旱的“残忍”实验。他们把骆驼拴在烈日下整整晒了8天，不给它一口水喝，这只骆驼体重减少了100多千克，肌肉萎缩，筋骨裸露。但令人惊讶的是，它很快就复原了。关于骆驼耐旱的秘密,至今没有一个令人满意的说法.
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.
译文：
骆驼可以行走数百英里，并在几天之内也不用喝水。
在今天的科学一刻中，我们将会学习骆驼是怎样在干燥的沙漠中生存的。
我们先从驼峰说起，和你所听说的不一样的是，骆驼并没有储存多余的水在这里。驼峰积聚着脂肪，为它们长距离的沙漠旅行提供能量。然而就是这些脂肪，可以帮助骆驼止渴。水就是这些脂肪燃烧所产生的副产物之一。这些额外的水进入骆驼的血液，增加其水分的供应。
骆驼不像我们那样出汗，这样也可以储存水分。骆驼的新陈代谢到晚上就会降低，让它的体温低于人类。出汗可以冷却我们自己，因此如果体温较低的话，对汗水的需求也会比较少。骆驼同样覆盖着厚重的皮毛，这些皮毛可以防止白天的热量进入体内。正因为骆驼如此擅长保持其身体的冷却，所以它可以走很长时间，却不会流很多汗。
骆驼同样也很擅长保持它们的血容量。我们人类一旦流失了身体百分之十二的水分，血液就会变得太浓稠以至于不能正常工作。可是骆驼的血液，总是可以坚持到让其脱水到其重量的百分之二十五。
另一个有助于骆驼储存水的东西就是鼻腔。当我们呼气的时候，我们会流失许多水蒸汽，被雾气模糊的车窗可以证明这一点。骆驼有额外的干燥鼻腔，可以凝聚每次呼吸的水分，让水分的蒸发的变少。
就如你所见，没有关于骆驼沙漠生存能力的单一解释。相反地，骆驼有一系列的适应能力。 |