An understanding of their present-day distribution takes us into zoogeography Major units of distribution are the zoological region or zoogeographical regions, areas defined largely by the past and present relations of the continent to each other. Each region is further subdivided into faunal or ecological units, depending on the criteria used.
There are six zoogeographical regions, each more or less embracing a major continental land mass and all have long been separated from one another by water (oceans and fresh-water bodies), mountain ranges or desert, so that, each region has evolved its distinctive and characteristic orders and families of animals.
These major distributional units were first recognised by Sclater (1858), modified by Huxley (1868), extended by Wallace (1876) and best described in a modern way by Darlington (1957) and others. The six zoogeographical regions are the Palaearctic, the Nearctic, the Neotropical, the Ethiopian, the Oriental and the Australian.
Because some zoogeographers consider the Neotropical and the Australian regions to be so different from the rest of the world, these two are of en considered as regions or realms equal to the other four combined. They are classified as Neogea (the Neotropical), Notogea (the Australian) and Metagea (the Palaearctic, Nearctic, Ethiopian and Oriental).
Moreover, two zoogeographic regions, namely the Palaearctic and the Nearctic are quite closely related, so the two often considered as one, the Holarctic. In fact, these two regions are similar in climate, vegetation, and in their faunal composition having animals like wolf, hare, moose (called elk in North America), caribou, wolverine and bison.
This largest region comprises the whole of Europe, Soviet Russia, Northern China, Japan, Northern Arabia (Persia) and narrow strip of coastal North Africa. It is subdivided into European, Mediterranean, Siberian and Manchurian subregions.
Its eastern parts have characteristic fauna of the following animal species: Rhacophorus (flying frog), Bombinator (fire-bellied frog), Agkistrodon halys (pit viper), Strix uralensis, Grus japonensis (crane), Aix galericulata, Erinaceus (hedgehog), Podoces panderi, Capricornis sumatraensis, Camelus ferus (camel), Bos mutus, Ailuropus (great panda), Panthera tigris altaica (tiger), Uncia uncia, Phoca sibirica (fresh-water seal), Pteromys volans, Equus hemionus (donkey) and Macaca fuscata (rhesus monkey).
The common fauna of Western Palaearctic include animal species like Clupea harengus (herring), Sardina pilchardus (fish), Gadus moirhua (codfish), Vipera ammodytes (viper snake), Chamaeleon chamaeleon (arboreal lizard), Pelecanus onocrotalus (pelecan), Fratercula arctica, Phoenicopterus ruber, Rangifer tarandus (caribou), Ovis ammon, Dama dama, Capra aegagrus, Odobenus rosmjrus (walrus), Ursus arctos, Lynx lynx (wild cat), Castor fiber (beaver), Hystrix cristata (porcupine), and Panthera pardus (leoparu).
This region comprises the North American continent south to the Tropic of Cancer (i.e., Greenland and North America). It is subdivided into Californian, Rocky mountain, Allegany and Canadian subregions. The Nearctic is the home of many reptiles and has more endemic families of vertebrates.
Characteristic fauna of this region include animal species as Ambly- stoma tigrinum, Crotalus adamanteus (rattle snake), Branta canadensis (Canadian goose), Larus schistisagus (gull), Bucephala albe- ola, Meleagris gallopavo (turkey), Didelphis marsupialis (opossum), Ovibos moschatus (musk-ox), Rangifer tarandus arcticus (Caribou), Bison bison (North American bison), Odobenus rosmarus divergens, Cystophora cristata, Martes pennanti (fisher), Lutra canadensis (otter), Dasypus novemcinctus (armadillo), Can is latrans, Proc yon lotor (racoon), Lagenorhynchus acutus, Delphinapterus leucas and Enhydra lutric.
It includes Central America, South America, part of Mexico and the West Indies. This region lacks well-developed ungulate fauna of the plains, but have rich, distinctive, varied endemic fauna of vertebrates.
Characteristic animals of this region are Lepidosiren (lung-fish), Lepidosteus (Gar- pike), Histrio histrio, tortoises (Dermatemys, Stourotypus, Peltoce- phalus), Heloderma horridum, -guana iguana, Amazilia yucatanensis, Phoenicopterus ruber, Pelicanus occidentalis (brown pelecan), Phala- crocorax harrisi, Sarcoramphus papa, Amazona amazonica, Spheniscus magellanicus, Chironectesminimus, Desmodus rotundus, Myrmecophaga tridactyla (giant anteater), Tapirus terrestris (tapir), Lama vicugna, Lama guanicoe, Panthera onca, Arctocephalus australis, Cavia aperea, Brady pus tridactylus (three-toed sloth), Vultur gryphus, Pterocnemia pennata and Ara macao.
The old world counterpart of the Neotropical is the Ethiopian, which includes the continent of Africa, south of the Atlas Mountain and Sahara Desert, Southern Arabia, Madagascar and Mauritius. It embraces tropical forests in central Africa and in the mountains of East Africa, Savanna, grasslands and deserts. It includes a varied vertebrate fauna and several endemic families.
The characteristic animals of this region are Proto- pterus (lung fish), Crocodilus niloticus, Sagittarius serpentarius, Struthio camelus (ostrich), Oryx gazella (African antelope), Giraffa camelopardalis (giraffe), Loxodonta africana (Africana elephant), Equus quagga.
Hippopotamus amphibius, Daubentonia madagascarien- sis (ayeaye). Lemur catta, Macaca sylvana. Pan troglodvtes (chimpanzee), Gorilla gorilla, Acinonyx jubatus, Panthera leo (lion), Hyaena hyaena, and Delphinus delphis. It lacks deer and bears among mammals and salamanders and tree-frogs among amphibians and contains several endemic families of birds.
It includes India, Indochina, South China, Malaya, and the western islands of the Malay Archipelago. It is bounded on the north by the Himalayas and on the other sides by the Indian and Pacific oceans on the southeast corner, where the islands of the Malay Archipelago stretch out toward Australia, there is no definite boundary, although Wallace’s line is often used to separate the Oriental from the Australian regions.
This line runs between the Philippines and the Moluccas in the north, then bends southwest between Borneo and the Celebes, then south between the islands of Bali and Lombok.
A second line, Weber’s line, has been drawn to the east of Wallace’s line; it separates the islands with a majority of Oriental animals from those with a majority of Australian ones. Since the islands between these two lines form a transition between the Oriental and the Australian regions, some zoogeographical the area Wallace (Smith, 1977).
The Oriental region is divided into the following four sub- regions: Indian sub-region, Ceylonese sub-region, Indo-Chinese sub region and Indo-Malayan sub-region. Its characteristic fauna includes the following animal species: Rhacophorus pardalis. Gavtahs niloticus (gharial), Calotes versicolor (garden lizard), Draco volans (flying lizard), Draco dussumieri (flying lizard), Python reticulatus, Naja naja (Indian cobra), Ophiophagus hannah, Gallus gallus (jungle fowl), Pavo crislatus (peacock), Milvus migrans (pariah kite), Eudynamys (Koel), Psittacula krameri (rose-ringed parakeet), Bubo bubo (great horned owl), Coracias benghalensis (blue jay), Dino- pium benghalense (golden-backed woodpecker), Corvus splendens (crow), Argusianus argus, Elephas maximus (elephant), Rhinoceros unicornis, Antelope cervicapra (black buk), Axis axis (spotted deer), Boselaphus tragocamelus (blue bull), Selenarctos tibetans (black Himalayan bear), Melursus ursinus (sloth bear) Sus cristatus (wild boar), Hystrix leucura (Indian porcupine), Herpestes (mongoose), Manis (pangolin), Soriculus (Indian shrew), Hyaena striata, Pan- thera tigris tigris, Panthera pardus, Babyrousa babyrussa, Macaca mulatto, Presbytis entellus (langoor), Pongo pygmaeus (orangutan), Ailurus fulgens, and Hylobates lar (gibbon).
This region includes Australia, Tasmania, New Guinea, and a few smaller islands of the Malay Archipelago. New Zealand and the Pacific Islands are excluded, for these are regarded as oceanic islands separate from the major faunal regions.
Partly tropical and partly south temperate, the Australian region is noted for its lack of a land connection with other regions; the poverty of fresh water fish, amphibians and reptiles; the absence of placental mammals and dominance of marsupials.
Included are the egg-laying mammals (monotremes) and the spinv ant-eaters. The characteristic fauna of this region includes following species: Neoceratodus (fish), Chelmon rostratus. Phvllopteryx eques, Omithorhynchus anatinus (platypus or duck mole), Zagoglossus hruijni(vroechdna), Techyglossus aculeatus (echidna, spiny ant-eater), Macropus giganteus (kangaroo), Notory- ctes typhlrps, Macrotis lagotis, Dmmaius novaehollandiae, Petaurus austalis, Paradisaea rubra, Pteridophcra alberti and Phaseclarctos cinereus (koala).
Abterrx owenii haasti (kiwi), etc. Sometime, South Polar Region called the Antarctic or Archinotic is also included in these major distributional units. Antarctic region has the following characteristic animal species: Balaenoptera musculus (blue whale), Orcinus orcam, Megadyptes antipodes, Aptenodytes patagonica (penguin). A. foresteri (emperor penguin), Pygoscelis adeliae, Diomedea exulans (albatross), Chionis Alba, and Lobodon carcinophagus.
Life Zones, Biotic Provinces and Biomes:
Each major distributional unit (i.e., Palearctic, etc.) is further subdivided by secondary barriers such as vegetation types and topography. The life-zone concept, restricted to North American, divides the continent into broad transcontinental belts: the plant and animal differences between these belts are governed chiefly by temperature.
The biotic provinces approach divides the North American continent into continuous geographic units that contain ecological associations different from those of adjacent units, especially at the species and subspecies levels. The biome system groups the plants and animals of the world into integral units characterized by distinctive life forms in the climax.
Boundaries of biomes or major life zones coincide with the boundaries of the major plant formations of the world. Thus, by including both plants and animals as a total unit that evolved together, the biome permits the recognition of the close relationship that exists among all living things.