A biome is a plant and animal ecosystem that covers a large geographical area. Complex interactions of climate, geology, soil types, water resources, and latitude all determine the kinds of plants and animals that thrive in different places. Fourteen major ecological zones, called “biomes,” exist over five major climatic regions and eight zoogeographical regions. Important land biomes include tundra, coniferous forests, deciduous forests, grasslands, savannahs, deserts, chaparral, and tropical rain forests.