Biome
A biome is a large region of Earth with a characteristic climate and community of plants and animals, such as tundra, desert, or tropical rainforest.
Definition
A biome is a very large area of Earth with a certain kind of climate and certain kinds of plants and animals, such as desert, rainforest, grassland, or tundra, and climate decides the biome, so knowing how hot and wet a place is usually lets you guess what grows there; the Sahara and the Mojave, though far apart, are both deserts, hot, dry, and home to plants and animals built to save water. More formally, a biome is a major type of ecosystem defined by climate, mainly temperature and precipitation, and by its dominant vegetation and adapted animal life, spanning major terrestrial types such as tropical rainforest, temperate deciduous forest, taiga, grassland, savanna, desert, and tundra plus freshwater and marine aquatic biomes, and the same biome can occur on several continents with different but similarly adapted species. At the biogeographic level, biomes are classified by the physiognomy of their dominant vegetation, which reflects the combination of temperature and precipitation summarized in the Whittaker biome diagram, and their global distribution follows atmospheric circulation, with rising equatorial air producing rainforest, descending dry air near $30^\circ$ latitude producing major deserts, and declining temperature toward the poles producing the forest-to-tundra sequence, while convergent evolution makes unrelated species in the same biome on different continents structurally similar.
Example
Most of North Carolina lies in the temperate deciduous forest biome, with warm summers, cool winters, and $100$ to $150\ \text{cm}$ of rain a year, while tundra has a growing season of only about $50$ to $60$ days and soil frozen below the surface. Cacti in the Americas and euphorbias in Africa evolved nearly identical succulent, spiny forms in separate desert biomes despite belonging to different plant families, and tropical rainforest covers about $6$ percent of Earth's land surface yet is estimated to hold around half of all terrestrial species.
Key Insight
Climbing a tall mountain near the equator carries you through the same sequence of biomes as traveling from the tropics to the poles, and because a biome is really a prediction, given the climate, ecologists can forecast vegetation structure and even animal body plans, which is exactly what makes biome maps useful for anticipating how ecosystems will respond to a warming climate.