The desert is a region of extremes. It is usually extremely dry, extremely remote and extremely hot. It can also be extremely cold at night (especially in the winter), extremely windy (especially in the summer), and prone to flash flooding in the spring.
Desert, term applied to regions of the earth that are characterized by less than 254 mm (10 in) of annual rainfall, an evaporation rate that exceeds precipitation, and, in most cases, a high average temperature.
Because of a lack of moisture in the soil and low humidity in the atmosphere, most of the sunlight penetrates to the ground.
Daytime temperatures can reach 55° C (131° F) in the shade.
At night the desert floor radiates heat back to the atmosphere, and the temperature can drop to near freezing.
Desert plants have evolve-d ways of conserving and efficiently using the water available to them.
Some flowering desert plants are ephemeral; they live for a few days at most. Their seeds lie dormant in the soil, sometimes for years, until a soaking rain enables them to germinate and quickly bloom.
Among the desert animals, the few amphibian species are capable of long-term dormancy during dry periods. When the rains come, they mature rapidly, mate, and lay eggs.
Many birds and rodents reproduce only during or following periods of winter rain that stimulate the growth of vegetation. Some desert rodents, such as the North American kangaroo rat and the African gerbil, feed on dry seeds; their metabolic processes are extremely efficient at conserving and recycling water, and their urine is highly concentrated. A number of desert mammals, such as the camel, are able to withstand considerable dehydration.
Most desert mammals and reptiles are nocturnal, remaining in cool underground burrows or in the shade by day.
Some desert reptiles, such as the horned toad, can control their metabolic heat production by varying their rate of heartbeat and the rate of body metabolism.
Some mammals, among them the desert oryx, vary their body temperatures, storing heat by day and releasing it at night.
LOCATION Location Name of desert Indian, Pakistan Thar S.W. USA, Mexico Sonoran North Africa Sahara Argentina, South America Monte S.W. USA Mojave S.W. Africa Kalahari Mexico/S.W. USA Chihuahuan Arabian Peninsula Arabian Desert Australia Great Sandy Desert, Great Victoria, Simpson, Gibson, Tanami