A deserts is an area that recieves less than 25 centimeter per year.
The amount of evaporationn adesertss greater than the amount of
precipitation.Some of the driest deserts may not recieve any precipi-
tation in ayear.Deserts often undergo large shifts in temperature
during the course of aday.Ascorching hot deserts like the Namib
Deserts in Africa cools rapidly each night when the sun goes down.
Other deserts,such as the Gobi in central Asia,are cooler,and even
experience freezing temperatures in the winter.Organisms that live
in the desert must be adapted to the lack of rain and extreme temper-
atures.For example ,the stem of a saguaro cactus has folds that work
like the pleats in an accordion.The stem expands to store water when
it is raining.Gila monsters can spend weeks at a time in their cool
underground burrows.Many other desert animals are most active
at night when the temperatures are cooler.