A biome is defined by the interactions of climate, geology, and local flora and fauna. These factors are influenced by geographical location. For example, regions near the equator are often hot, wet and teeming with life, while those far from the equator are typically cold arid and fairly devoid of life.
Scientists disagree on the exact number and definition of the world's biomes. However, there is general consensus that there are at least five distinct biomes: aquatic, deserts, forests, grasslands and tundra. Each of these hosts different forms of life adapted to the challenges of the biome.
These five biomes are often further divided for more precise classification. Grasslands can be split into savanna and grassland, while forests can be labeled as alpine, taiga, deciduous and rainforest. Because of the subtle interactions between plants, animals and the environment, no two areas are exactly alike, even if they are assumed to be within the same biome. The Pacific temperate rainforest of the northwest United States has a vastly different ecosystem than those of South America, which are again quite different from rainforests in southern Asia. This diversity creates challenges in classifying biomes, as different scientists focus on different aspects in identification.