From rainforests, deserts, and savannas in the tropical and subtropical regions, to the boreal forests, tundra, and taiga as we approach the poles, the Earth's continents are covered by a mosaic of complex biological communities. These ecosystems are the biological reactions to the interactions between climate, geology, and topography, which set the conditions on which organisms (from bacteria, to fungi, to animals, algae, and plants) will grow. The resulting community living in a specific area of the planet will be defined not only by the physical characteristics of a region (climate, geology, topography), but also by the adaptations of the organisms that make them successful under these conditions.

Based on temperature and precipitation, the world is divided in ## regions (or BIOMES) with characteristic biological communities.