A desert biome is an area that receives less than twenty-five centimeters of rainfall a year. Most people think of the desert as always being hot, but a desert can actually be hot or cold. There is a great difference between daytime and nightime temperatures. In a cold desert, daytime temperatures during the winter may be below freezing. Freezing is the last thing that you need to worry about as you walk through the the burning sands of the Sahara Desert.
You cannot help but notice that the plants in the desert are adapted to the lack of rainfall. Many have widespread roots that are close to the surface. This enables the roots to absorb water quickly, before it evaporates. Even though you look hard in the Sahara Desert, you see very few animals. There are a lot of animals in the desert that you do not know about. In the daytime lizards and small rodents often escape the heat by going into underground burrows. Here the temperature may be as much as thirty degrees Celsius cooler than at the surface. Night brings animals to the surface searching for food. Like plants, desert animals must live on as little water as possible. Most of the water used by desert animals comes from the seeds and stems of plants, which are about fifty percent water. The most famous desert animals-camels-can live without water if there are enough plants available for them to eat. Camels can get along without having water for up to ten days. During this time, they live off the water stored in the body fat in their humps. Only in this way can they survive in a world where rain hardly ever falls.