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The tundra is a very dry biome. How is different from the desert and grassland biomes, which also tend to be very dry?
The tundra is very cold. It is covered in a layer of permafrost (frozen soil). Most of the soil is frozen all year. There is a short period os soil when the permafrost melts, but the soil underneath remains frozen, so small ponds and lakes form. Deserts receive a little more rainfall than the tundra, and the grassland might receive a little more than the desert. Both the desert and the grassland biomes can to be pretty warm, but the desert can have huge temperature shifts from day to night, and some can experience freezing temperatures in winter. Deserts are very dry (they have more evaporation than precipitation), and organisms must adapt to temperature extremes and dry conditions. In the grassland temperatures are a little more comfortable and there is less variation in temperature, but there is still not enough rainfall for trees to grow. Prairies are grasslands located a little farther away from the equator, but savannas, closer to the equator, receive a little more rainfall than prairies. Grasslands are home to some of the largest animals on earth (many large herbivores), because of all of the grass to graze on. Their grazing actually helps maintain the grassland, because they keep young trees and bushes, which would use up a lot of water, from sprouting.