A biome is defined as a regional ecosystem containing a distinctive group of flora and fauna that has developed to suit the environment's specific climatic and soil conditions. There are five kinds of biome on planet earth: aquatic, forest, grassland, tundra and desert. Desert biomes cover approximately one-fifth of the world's surface.
Desert biomes are characterized as regions which receive less than 20 inches of rainfall annually, but most only receive around half that amount. There are four types of deserts. Hot and dry deserts are warm throughout the year, with very hot summers and extremes in temperatures between night and day. Semiarid deserts have moderately dry, long summers with low concentrations of rainfall. Coastal deserts have cool winters followed by long, warm summers. Cold deserts have long chilly winters and although they receive more precipitation than other types of deserts through snow and rainfall, the amount is less than 20 inches annually.
According to ThinkQuest, around 8.6 million square miles of the earth's surface is covered with desert biomes, most of which are geographically in the middle of continents between 25 to 40 north and south latitude. Hot and dry deserts are situated in North America, South and Central America, Southern Asia, Africa and Australia. The Nearctic region, consisting of North America, Northern Asia and Europe, is where semiarid deserts are located. Greenland, the Antarctic and Nearctic regions are where cold deserts are found. Coastal deserts are located on the western sides of continents near the Tropics of Capricorn and Cancer, where the climate is influenced by cold ocean currents.
Animals living in desert biome habitats have developed special adaptations which enable them to deal with the extreme temperatures, lack of water and available food supply. Most animals living in desert biomes are burrowers. Most of the animals which thrive in hot, semiarid and coastal deserts, burrow underground to stay cool and are nocturnal to avoid the heat of day. Cold desert animals including badgers, foxes, rats and mice burrow underground for warmth. Because of the limited amount of precipitation in deserts, some animals like the addax, tortoises and lizards get their water through the food that they eat. Other animals, including the Egyptian spiny-tailed lizard and the Gila monster, store fat in their bodies to keep themselves hydrated.
Like animals, plants have also evolved to survive in the climatic and soil conditions characteristic of desert biomes. In hot and dry deserts, short woody trees and ground-hugging shrubs with water-saving capabilities are the main form of plant life, according to the University of California Museum of Paleontology. Spiny and woolly desert plants with silvery or glossy leaves are characteristic of semiarid deserts, these features protecting the plants from the harsh weather conditions. The fine, salty soil of coastal deserts features plant life capable of storing water in extensive root systems or thick fleshy leaves. Cold deserts have only scattered vegetation since even their warmest temperatures allow only few mosses, lichens and grasses to grow.