 
Desert biomes are characterized by their lack of moisture. Usually less than 25 cm of precipitation falls in a year, and in some locations (like the Sahara desert) it's less than 2 cm per year.There are few plants that can grow here; the ground is bare during much of the year. With little surface material available to retain the heat from sunlight, the nights are quite cold. Plants that exist here are able to retain water, both by storing it in their tissues and by preventing its loss, through adaptations like thick waxy skin and thorns to ward off animals. Animals also are adapted to the heat and dry conditions; many are active only at night, and those that are out in daytime are able to conserve water. The camel, for example, maintains a supply of water bound into the fat in its hump(s). Other creatures can exist with little need for water intake.   Plant life includes succulent ('water-rich') plants like cactus, as well as plants that are tolerant of little water, like sagebrush and mesquite. Animal life includes millipedes, centipedes, spiders, snakes and lizards, as well as goats, sheep, coyotes and camels. There are also running birds like the roadrunner and ostrich, as well as bats and other small mammals. In the few locations where ground water is available, the vegetation may be more lush; these areas are called oases. |