The desert has less than 254 mm of annual rainfall. Because of the lack of moisture in the soil and low humidity in the atmosphere, most of the sunlight penetrates to the ground. The evaporation rate exeeds precipitation, and in most cases, a high average temperature.
Among the desert animls, the few amphibian species are capable of long term dormancy during dry periods. Some animals use their metabolic processes that are extremely efficient at conserving and recyclying water, and their urine is highly concentrated.
A number of animals can withstand the dehydration.
The heat is a large problem in the desert. Most animals such as reptiles burrow themselves underground to keep cool. Some desert mammals, vary their body temperatures, storing heat by day and releasing it at night.
Some flowering desert plants are ephemeral; they live for a few days at the most because of the lack of water and the intensity of heat. Since the desert doesn't have that much rainfall, seeds from plants don't even sprout for years which effects the wildlife.
Humans contribute to destroying the desert by mining waterholes and letting them soak up. Burning and overgrazing of semi-arid lands on the edges of deserts can irreversibly damage the plants that hold moisture and hold the soil together, thus enabling deserts to spread to usuable land.