Large animals that inhabit the desert have evolved a number of adaptations
for reducing the effects of extreme heat. One adaptation is to be light in
color, to reflect other than absorb the sun’s rays. Desert mammals also depart 62. ______
from the normal mammalian practice of maintaining a continuous body 63. ______
temperature. Instead of trying to keep down the body temperature deep inside the
body, and which would involve the expenditure of water and energy, desert . ______
mammals allow their temperatures to rise to what would normally be fever
height, and the temperature as high as 46 degrees Celsius have been measured 65. ______
in Grant’s gazelles. The overheated body then cools down during the cold
desert night, and indeed the temperature may fall usually low by dawn, as
low as 34 degrees Celsius in the camel. This is the advantage since the heat of 66. ______
the first few hours of daylight is absorbed in warming up the body, and an
excessive buildup of heat does begin until well into the day. 67. ______
Another strategy for large desert animals is to tolerate the loss of body
water to a place that would be fatal for nonadapted animals. The camel can 68. ______
lose up to 30% of its body weight as water without harm to itself, when 69. ______
human beings die after losing only 12% to 13% of their body weight. An
equally important adaptation is the ability to replenish (补充) this water loss
for one drink. The tolerance of water is of obvious advantage in desert, as 70. ______
animals do not have to remain near a water hole but can obtain food by grazed in 71. ______
sparse and far-firing pastures.