These sorts of observations were made by early biogeographers who recognized certain types of distri

These sorts of observations were made by early biogeographers who recognized certain types of distri

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These sorts of observations were made by early biogeographers who recognized certain types of distributions of organisms. Some species are restricted to a certain region and are referred to as endemic species . Endemism needs to be defined with relation to the taxonomic group: all life forms we know are endemic to the planet earth; the genus Geospiza (Darwin's finches) are restricted to the Galapagos islands; Geospiza fortis is endemic to specific islands; the spotted owl is endemic to the old-growth forests of the pacific northwest. Cosmopolitan species have a world wide distribution. They may be restricted to specific habitats, but occur on most continents. In addition to endemism, another important pattern that needed to be explained were examples of disjunct distributions where clearly related species (or even the same species) are found in different
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Unformatted text preview: areas. Marsupials are found in Australia and South America. Ratite birds (Ostrich, Emu&Cassowary, Rhea) are found in Africa, Australia and South America, respectively. Alfred Russell Wallace noticed that different regions of the world had congruent patterns of endemic species and he drew up six biogeographic realms (see fig. 18.2, pg. 510; nearctic, neotropical, holarctic, ethiopian, oriental and australian). Wallace worked primarily in Malaysian region and had noticed a clear break between Australian fauna and the fauna on the islands to the northwest. This break has come to be known as Wallace's line (also a line between the Australian and the Asian biogeographic zones). These patterns described long before continental drift was an issue...
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