The document defines biomes as major terrestrial ecosystems classified based on regional climate. It describes the key abiotic and biotic factors that characterize several major biomes including tropical rainforests, tropical dry forests, tropical grasslands/savannas, deserts, temperate grasslands, temperate woodlands/shrublands, temperate forests, northwestern coniferous forests, boreal forests, and tundra. Each biome is defined in terms of its climate, soil, characteristic plant and animal life, and adaptations required to survive within the biome.