A biogeographic realm or ecozone is the broadest

biogeographic Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, ...

division of Earth's land surface, based on distributional patterns of terrestrial organisms. They are subdivided into

bioregion A bioregion is an ecologically and geographically defined area that is smaller than a biogeographic realm, but larger than an ecoregion or an ecosystem, in the World Wide Fund for Nature classification scheme. There is also an attempt to use the ...

s, which are further subdivided into ecoregions.

Description

The realms delineate large areas of Earth's surface within which organisms have evolved in relative isolation over long periods of time, separated geographic features, such as oceans, broad deserts, or high mountain ranges, that constitute

natural barrier A natural barrier refers to a physical feature that protects or hinders travel through or over. Mountains, swamps, deserts and ice fields are among the clearest examples of natural barriers. Rivers are a more ambiguous example, as they may obstruc ...

s to migration. As such, biogeographic realm designations are used to indicate general groupings of organisms based on their shared biogeography. Biogeographic realms correspond to the floristic kingdoms of

botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...

or zoogeographic regions of zoology. From 1872,

Alfred Russel Wallace Alfred Russel Wallace (8 January 1823 – 7 November 1913) was a British naturalist, explorer, geographer, anthropologist, biologist and illustrator. He is best known for independently conceiving the theory of evolution through natural sele ...

developed a system of zoogeographic regions, extending the

ornithologist Ornithology is a branch of zoology that concerns the "methodological study and consequent knowledge of birds with all that relates to them." Several aspects of ornithology differ from related disciplines, due partly to the high visibility and th ...

Philip Sclater Philip Lutley Sclater (4 November 1829 – 27 June 1913) was an English lawyer and zoologist. In zoology, he was an expert ornithologist, and identified the main zoogeographic regions of the world. He was Secretary of the Zoological Society ...

's system of six regions. Biogeographic realms are characterized by the evolutionary history of the organisms they contain. They are distinct from

biome A biome () is a biogeographical unit consisting of a biological community that has formed in response to the physical environment in which they are found and a shared regional climate. Biomes may span more than one continent. Biome is a broader ...

s, also known as major habitat types, which are divisions of the Earth's surface based on ''life form'', or the adaptation of animals, fungi, micro-organisms and plants to climatic, soil, and other conditions. Biomes are characterized by similar

climax vegetation In scientific ecology, climax community or climatic climax community is a historic term for a community of plants, animals, and fungi which, through the process of ecological succession in the development of vegetation in an area over time, ha ...

. Each realm may include a number of different biomes. A

tropical moist broadleaf forest Tropical and subtropical moist broadleaf forests (TSMF), also known as tropical moist forest, is a subtropical and tropical forest habitat type defined by the World Wide Fund for Nature. Description TSMF is generally found in large, discon ...

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, micro-organisms and plants with very different evolutionary histories. The distribution of organisms among the world's biogeographic realms has been influenced by the distribution of

landmass A landmass, or land mass, is a large region or area of land. The term is often used to refer to lands surrounded by an ocean or sea, such as a continent or a large island. In the field of geology, a landmass is a defined section of contine ...

es, as shaped by plate tectonics over the

geological history of the Earth Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other E ...

Concept history

The "biogeographic realms" of Udvardy were defined based on taxonomic composition. The rank corresponds more or less to the

floristic kingdom A phytochorion, in phytogeography, is a geographic area with a relatively uniform composition of plant species. Adjacent phytochoria do not usually have a sharp boundary, but rather a soft one, a transitional area in which many species from both re ...

s and

zoogeographic region Zoogeography is the branch of the science of biogeography that is concerned with geographic distribution (present and past) of animal species. As a multifaceted field of study, zoogeography incorporates methods of molecular biology, genetics, mor ...

s. The usage of the term "ecozone" is more variable. It was used originally in stratigraphy (Vella 1962, Hedberg 1971). In Canadian literature, the term was used by Wiken in macro level

land classification Regionalisation is the tendency to form decentralised regions. Regionalisation or land classification can be observed in various disciplines: *In agriculture, see Agricultural Land Classification. *In biogeography, see Biogeography#Biogeograph ...

, with geographic criteria (see

Ecozones of Canada Canada has 20 major ecosystems -- ecozones, comprising 15 terrestrial units and 5 marine units. These ecozones are further subdivided into 53 ecoprovinces, 194 ecoregions, and 1,027 ecodistricts. These form the country's ecological land class ...

). Later, Schültz would use it with ecological and physiognomical criteria, in a way similar to the concept of

. In the

Global 200 The Global 200 is the list of ecoregions identified by the World Wide Fund for Nature ( WWF), the global conservation organization, as priorities for conservation. According to WWF, an ecoregion is defined as a "relatively large unit of land or w ...

/WWF scheme, originally the term "biogeographic realm" in Udvardy sense was used. However, in a scheme of

BBC #REDIRECT BBC Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board exam. ...

, it was replaced by the term "ecozone".

Terrestrial biogeographic realms

Udvardy biogeographic realms

WWF / Global 200 biogeographic realms

The World Wildlife Fund scheme is broadly similar to

Miklos Udvardy Miklos Dezso Ferenc Udvardy (March 23, 1919 – January 27, 1998) was a Hungarian-American biologist and university instructor. He contributed to a wide variety of disciplines, such as biogeography, evolutionary biology, ornithology, and veget ...

's system, the chief difference being the delineation of the Australasian realm relative to the Antarctic, Oceanic, and Indomalayan realms. In the WWF system, the Australasia realm includes Australia, Tasmania, the islands of Wallacea, New Guinea, the

East Melanesian Islands The East Melanesian Islands, also known as the Solomons-Vanuatu-Bismarck moist forests, is a biogeographic region in the Melanesia subregion of Oceania. Biogeographically, the East Melanesian Islands are part of the Australasian realm. It is notabl ...

, New Caledonia, and New Zealand. Udvardy's Australian realm includes only Australia and Tasmania; he places Wallacea in the Indomalayan Realm, New Guinea, New Caledonia, and East Melanesia in the Oceanian Realm, and New Zealand in the Antarctic Realm. The Palearctic and Nearctic are sometimes grouped into the

Holarctic realm The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical regi ...

Morrone biogeographic kingdoms

Following the nomenclatural conventions set out in the International Code of Area Nomenclature, Morrone defined the next biogeographic kingdoms (or realms) and regions: * Holarctic kingdom Heilprin (1887) ** Nearctic region Sclater (1858) ** Palearctic region Sclater (1858) * Holotropical kingdom Rapoport (1968) ** Neotropical region Sclater (1858) ** Ethiopian region Sclater (1858) ** Oriental region Wallace (1876) * Austral kingdom Engler (1899) ** Cape region Grisebach (1872) ** Andean region Engler (1882) ** Australian region Sclater (1858) ** Antarctic region Grisebach (1872) * Transition zones: ** Mexican transition zone (Nearctic–Neotropical transition) ** Saharo-Arabian transition zone (Palearctic–Ethiopian transition) ** Chinese transition zone (Palearctic–Oriental transition zone transition) ** Indo-Malayan, Indonesian or Wallace's transition zone (Oriental–Australian transition) ** South American transition zone (Neotropical–Austral transition)

Freshwater biogeographic realms

The applicability of Udvardy scheme to most freshwater taxa is unresolved. The drainage basins of the principal oceans and seas of the world are marked by continental divides. The grey areas are endorheic basins that do not drain to the ocean.

Marine biogeographic realms

According to Briggs and Morrone: According to the WWF scheme:

References

{{Biomes Biogeography Habitat