Desert
About 20% of earth is covered with deserts. Deserts receive very little rainfall year round. During the day it's really hot, but once the night arrives the temperature drops very low. Most of the deserts animals are nocturnal, which means they sleep during the day and are up during the night, and contain water in their bodies or receive it from their food supply.
http://www.softschools.com/facts/biomes/desert_biome_facts/167/
http://www.softschools.com/facts/biomes/desert_biome_facts/167/