21 Survival of Desert Life 沙漠生命的延续

            21
             Survival of Desert Life 沙漠生命的延续

① Some desert animals can survive the very strong summer heat and dryness because they have very unusual characteristics.The camel,
            for example,can hear an increase in the temperature of its body and its blood of 9℃.In addition,it can drink an enormous amount of water in its red blood cells and other parts of its body to supply its needs for two weeks or more.The kangaroo rat,on the other hand,obtains all the water it needs from water that it produces during respiration.However,most animals need to maintain a fairly constant body temperature,and will die If it rises more than 5℃.Therefore,they must find some way to avoid the strong sun rays.Nor can many animals either store or produce water in their bodies,as the camel and kangaroo rat can.So they must find ways to reduce water loss from their bodies to the lowest degree.

② Because very few desert animals can survive the high rays,the temperature,and the evaporation rate of a typical summer‘s day,most of the them are active during the night.Only after the sun has set does the desert come fully to life.The night is relatively cool,and the darkness provides protection,not only from the sun,but also from other animals and birds.So the coming of darkness is the signal for water and food.When morning comes,most of them seek shelter again.Many go under ground;nearly all find somewhere shady and they can avoid the sun rays there.
③For many kind of insects,living in the desert is easier than for animals.Like many desert plants,they have a waterproof skin which prevents water loss by evaporation.In addition,some insects spend all or most of life below ground.Here,for most of the year at least,there is some wetness,and it is generally cooler than on the surface.