SOME CONSEQUENCES OF EVOLUTIONARY RELATIONSHIP 



373 



flying squirrel, also occurs in this region. It is also a species, but sufficiently 

 different from the other two to be placed not in the "squirrel" category 

 but in a separate one, "flying squirrel." Again, among the birds of this 

 region are two sorts of crows, the fish crow and the common crow. Both 

 of these are species, but they show so many similarities that we group 

 them together as "crows." These larger categories in which we group 

 similar species are called genera (singular genus). The fox squirrel and 

 gray squirrel belong to one genus, the flying squirrel to another, and the 

 two crows to a third. 



The naming of organisms. People sometimes ask why biologists give strange 

 Latin names to animals and plants, instead of using the common names "that 

 everyone can understand." The reasons are two. First, only a few species have 



Fig. 24.11. The gray squirrel, Sciurus caro- 

 linensis. (Courtesy Zoological Society of 

 Philadelphia.) 



Fig. 24.12. The flying squirrel, Glaucomys 

 volans. (Courtesy Zoological Society of 

 Philadelphia.) 



common names; most are nameless and unknown until they are described by some 

 biologist. Second, it is very naive to think that the common names used in the 

 United States will be intelligible to scientists in France, England, Germany, 

 Russia, and Japan. Even within a single country the vernacular names are neither 

 precisely used nor everywhere the same. A single species may bear a dozen or 

 more names in different regions, while one name may be applied to many similar 

 species and sometimes to very different ones. Thus in the North and West 

 "gopher" means a small burrowing rodent, while in Florida and other parts of the 

 South it means a tortoise. 



Each species has only one valid technical or "scientific" name, by which it is 

 known to scientists of all countries and all times. 1 This name consists of two 



1 This is the ideal. In practice a considerable number of names have to be changed 

 at one time or another in order to eliminate synonymy or to conform to the rules 

 governing nomenclature. 



