Zoogeography

ZOOGEOGRAPHY, the science that studies the distribution of animals over the Earth's surface and its dependence on various conditions. Zoogeography is divided into general and special. General zoogeography examines the general regularities of animal distribution, its connection with climatic conditions, vegetation, and relief of the terrain, the significance of food, migrations, barriers preventing the mixing of faunas, the distribution of animals in the past, and its dependence on the configuration of the Earth's surface. Special zoogeography, according to the arrangement of material, can be divided into proper zoological geography, i.e., the study of faunas inhabiting various countries taken as a whole, and geographical zoology, i.e., the study in systematic order of the geographic distribution of individual groups of animals (e.g., mollusks, mammals, etc.). Zoogeography is further subdivided into the zoogeography of land and marine animals. The foundations of modern zoogeography of terrestrial animals were laid by Sclater (1865) and Wallace (1876). It is customary to divide the land surface into several large sections, regions (or realms), which in turn consist of smaller subregions. Wallace recognizes the following six regions: 1) Australian (with adjacent islands of the Pacific Ocean), 2) Indian, or Oriental (India, Indochina, Malacca, and the Malay Archipelago), 3) Ethiopian (Africa, except the northern coast), 4) Neotropical (South and Central America with the Antilles), 5) Nearctic (North America to Mexico), and 6) Palearctic (Europe, northern coast of Africa, and all of northern Asia). In view of the significant similarity of Nearctic and Palearctic faunas, these two regions are often combined (Heilprin, 1882) into one—the Holarctic. At the initiative of Lydekker (1897), the majority of scientists accept the division of land into three units of the highest order, calling them realms: 1) Notogaeic—corresponding to the Australian Region; 2) Neogaeic—coinciding with the Neotropical Region; 3) Arctogaeic—embracing the other regions. The distribution of marine animals is somewhat less strict. The simplest of the modern divisions of marine fauna (Dahl, 1921) comprises four regions: Arctic, Antarctic, Indo-Pacific, and Atlantic. Vertical zonation plays a major role in the distribution of marine organisms. In all seas, four zones are distinguished: the coastal, or littoral; the shallow-water, down to depths of 200 m; the deep-water, or abyssal; and the open sea zone. The deep-water fauna exhibits considerable uniformity everywhere, as a result of which Ortmann distinguishes it into a separate abyssal region. According to their relationship to the bottom of a body of water, aquatic animals are divided into bottom-dwelling, or benthic, and constantly swimming in the water, or planktonic. Zoogeography is of great, mainly epidemiological interest to the physician, providing him with basic information on the geographic distribution of animal vectors and pathogens of various diseases. From this perspective, the greatest importance belongs to special chapters of zoogeography concerning individual groups of insects, worms, mammals, and some others, which constitute a part of medical geography.