A biome is a living of organisms in an ecological region. Each biome has different organisms for of life in that biome. There are major biomes that portions of the earth's land surface. Deserts, by extreme temperatures and little , cover about 20 percent of the surface of the earth. Rainforests, characterized by high levels of , constant temperatures, and amounts of precipitation, cover about 6 percent of the earth's land. The taiga belt, characterized by forests and cold temperatures, cover 17 percent of the earth's land. Most of the rest of the earth's land is covered by temperate forests, tundra, ice, and chaparral.