DESERTS ZONES

• Deserts experience some of the world's highest temperatures but perhaps more suprisingly they also undergo some of the greatest temperature contrasts to be found on the planet.

• The sun beating down through clear desert skies causes the temperature in the desert to soar. But when night falls there is no cloud cover to prevent the heat radiating from the ground escaping.

• Deserts occur when the annual rainfall is less than about 25 centimetres (10 inches), though some deserts are colder and drier than others. The most famous desert in the world is the Sahara.

• The impact of man plays a part too – by removing trees and protective vegetation, and introducing livestock there is also some evidence that deserts are extending.

• Many such as the Australian Aborigines and the Tuareg of North Africa have survived as nomads, wandering after food as best they can.

• Occasionally oases exist such as the remarkable oasis at the Gorges du Todra in Morocco where the greenness caused by a high water table is in stark contrast to the aridity around it.

-The cactus it has a tough outer skin to resist the heat and is able to store large amounts of water on the rare occasions when rain falls. Only the hardiest of plants can survive the deserts

Another hardy desert beast is the camel, which can store great amounts of water to sustain it for long periods. The camel also has the capacity to foam at the mouth when it overheats.

• The camel also has the capacity to foam at the mouth when it overheats. This foam spreads over parts of the animal's body and then evaporates in the sun, so reducing its temperature.