Biomes are large land areas defined by climate and plant life. The tundra is always cold while the desert is dry and hot, with large temperature variations possible. The tundra has mostly small, low-growing plants while the desert supports some large treelike plants. The tundra has the coldest temperatures while the rainforest has the most rain and most diverse plants and animals. Grasslands are located in the centers of continents, while tropical rainforests are near the equator and taigas and tundra are near the north and south poles.