CHOROLOGY. – The term c. (from χώρα, land, and λόγος, discourse) designates the study of the geographical distribution of living beings: thus, zoogeography is distinguished for animals and phytogeography for plants. Such distribution, or the spread of faunas and floras, depends primarily on *current* or *ecological factors*, i.e., the present existence of suitable climatic and environmental conditions; it also depends, however, on *historical* or *geographical factors*, i.e., the geological and climatic vicissitudes undergone by the Earth’s crust throughout its history. Thus, separations of continents and islands that occurred in certain geological eras may explain the absence or presence of particular zoological groups, depending on the epoch in which these groups first appeared on Earth; and changes in climatic conditions can account for the reductions or fragmentations of the distribution areas of many species that once had a more extensive geographical range. Human activity can also significantly alter the distribution of faunas and floras.
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