Desert

When people think of a desert, they think of hot, sandy regions in which no life exists and it never rains. However, a desert is a biome, or type of environment, in which there is rainfall and life. It is just that in a desert, the amount of annual rain never exceeds more than 254mm, and the evaporation rate is higher than the precipitation rate. Often, in the desert, the temperature is fairly high and has been known to reach up to 131 degrees Fahrenheit during the day. Yet, it can also drop near to 32 degrees Fahrenheit by nightfall.

Deserts, caused by wind patterns and climate, are often located in regions along both the Tropic of Cancer and the Tropic of Capricorn. Deserts are composed of sand, but not the same sand as found on beaches, desert sand is larger and rounder. There are 22 deserts located in the world. Among these, the largest and most recognized is the Sahara Desert. The Sahara covers most of Northern Africa, and although it has usual high temperatures, it has been known to snow there before. Although the weather and land formation of a desert may seem impossible to live in, there are many different species that make their homes in the sand dunes of the world's 22 deserts.

Majority of desert species are from the class Reptilia, scale-covered animals who are adapted to fully terrestrial life. The Dipsosaurus dorsalis (desert iguana) is a common inhabitant of the Patagonia desert in Argentina. Found in the Arabian desert is the Camelus dromedarius (Arabian camel). The camel is one of the few species belonging to the class Mammalia (hair-covered animals who carry unborn fetus) that can withstand the climate of the desert. The camel can intake large amounts of water, and is able to store it for long amounts of time in either one or two humps on its back. The Caltype costae, Costa's hummingbird, also lives in the desert. The Costa's hummingbird represents the class Aves (endothermic, feathered birds).

One of the species of the desert that belongs to the class Aves, is an endangered species, the Colinus virginianus ridgwayi (Bobwhite masked quail). The Bobwhite struggles to survive in the Sonoran Desert, located in southwestern U.S. This is due to the recent invasion of woody plants in the desert. Also living in the desert, is the Centruroides sculpturatus (Bark scorpion). It is an invertebrate containing an exoskeleton and jointed appendages that belongs to the phylum Arthropoda. Another invertebrate associated with the desert is the Achatina fulica (African land snail) who, because of its soft body, belongs to the phylum Mollusca.

A representative of Cyanophyta, a blue-green algae, belongs to the kingdom Monera. Blue-green algae is usually found in crevices of desert rocks. Cyanophyta is involved in a symbiotic relationship with the fungus Lescanora esculenta. This relationship is the basis for a species of desert lichen, usually classified by the name of the fungus with which it is made.

Belonging to the kingdom Plantae is the Schulumbergers bridgesii, more commonly referred to as a Christmas cactus. Another desert organism belonging to the kingdom Plantae is the giant Saguaro Cactus. Cacti have the ability to retain water, which enables them to go without water for long periods of time. This is an adaptation because rainfall in the desert is scarce and absorbing and retaining the rainfall is the only way to acquire water. Aside from cacti, the desert is also home to many shrub like trees, such as Paloverde. These and many other species are what make the desert more than just a hot, sandy region of the world.

Source: http://nhs.needham.k12.ma.us/cur/Bio96_97/P3/desert/desertjk.html