SOME CONSEQUENCES OF EVOLUTIONARY RELATIONSHIP 



375 



the scheme, and called by such names as tribes, sections, groups, and the 

 like; there is no standard set of terms for such extra subdivisions. The 

 principal taxonomic categories are illustrated in the accompanying dia- 

 gram, which shows the classification of the five species previously 

 mentioned. 



PLANT KINGDOM-*- 



■PROTISTA- 



-►ANIMAL KINGDOM 



the plant phyla and 

 their subdivisions 



Phylum 

 Chordata 



Subphylum 

 Vertebrata 



other 

 subphyla 



Class Mammalia 

 (mammals) 



Class Aves 

 (birds) 



other 

 classes 



other 

 subclasses 



other 

 orders 



Subclass 

 Eutheria 



(placenta Is) 



Order 

 Rodentia 

 (rodents) 



Order Passeres 

 (perching birds) 



other 

 families 



Family Sciuridae 

 (squirrels) 



other 

 genera 



Family Corvidae 

 (crows, blue jays, etc. ) 



Genus 



Sciurus 



(squirrels) 



Genus 



Glaucomys 



(flying squirrels) 



Genus 

 Corvus 

 ( crows ) 



Sciurus 



niger 

 (fox squirrel) 



Sciurus 



carolinensis 



(gray squirrel) 



Glaucomys 



volans 



(flying squirrel) 



other animal 

 phyla 



other 

 orders 



other 

 families 



other 

 genera 



Corvus 

 brachyrhynchus 

 (common crow) 



Corvus 



ossifragus 

 (fish crow) 



Fig. 24.13. Diagram showing the principal taxonomic categories. 



The methods and aims of taxonomy. If the main object of classifica- 

 tion were the naming, cataloguing, and identifying of species, any con- 

 venient artificial system would suffice. At this«level taxonomy is no more 

 a science than is a card file. However, modern taxonomy has the status 

 of a science because it is an attempt to discover and express the relation- 



