 Biogiographic ru-elm, a biogiographic ru-elm or echizone is the broadest biogiographic division of the Earth's land surface, based on distributional patterns of tristrial organisms. They are subdivided in ecorgens, which are classified in biomes or habitat types. The ru-elms delineate large areas of the Earth's surface within which organisms have been evolving in relative isolation over long periods of time, separated from one another by geographic features, such as oceans, broad deserts, or high mountain ranges, that constitute barriers to migration. As such, biogiographic ru-elms' designations are used to indicate general groupings of organisms based on their shared biogiography. Biogiographic ru-elms correspond to the floristic kingdoms of botany or zoogiographic regions of zoology. Biogiographic ru-elms are characterized by the evolutionary history of the organisms they contain. They are distinct from biomes, also known as major habitat types, which are divisions of the Earth's surface based on life form, or the adaptation of animals, fungi, microorganisms and plants to climatic, soil, and other conditions. Biomes are characterized by similar climax vegetation. Each realm may include a number of different biomes. A tropical moist broadleaf forest in Central America, for example, may be similar to one in New Guinea in its vegetation type and structure, climate, soils, etc., but these forests are inhabited by animals, fungi, microorganisms and plants with very different evolutionary histories. The patterns of distribution of living organisms in the world's biogiographic ru-elms were shaped by the process of plate tectonics, which has redistributed the world's land masses over geological history.