310 INTRODUCTION TO EVOLUTION 



The more or less doglike animals comprising genus Canis and genus 

 Vulpes, and some others, are grouped together into a higher category in 

 our classification known as the family. The particular family concerned 

 here is named Canidae (Fig. 14.1). Another convention is evident at this 

 point: the names of families always end with "-idae." 



Order 



Another family somewhat related to the Canidae is that called FeUdae, 

 including all the catlike animals. This family, like the former, is composed 

 of several genera (plural of "genus"), each of which is subdivided into 

 species. The genus Felis has already been mentioned; in addition to the 

 species concolor within it, we may call attention to the species name of the 

 common house cat: domestica. Thus our pet is known to science as Felis 

 domestica. Other families include the Ursidae (bears), Procyonidae (rac- 

 coons), Hyaenidae (hyenas). 



All the animals mentioned in the preceding paragraph are alike in some 

 respects, some of the most striking similarities being connected with the 

 nature of their diet. They are all carnivorous — flesh eaters. This fact is 

 recognized in classification by grouping these families together into a 

 larger unit of classification, the order. They all belong to Order Carnivora 

 (Fig. 14.1). 



Class 



A dozen or so other orders of mammals rank along with the Carnivora. 

 For example. Order Rodentia (gnawing animals) and Order Lagomorpha 

 (hares and rabbits) were mentioned in connection with serological studies 

 (pp. 117-119). Human beings, apes, and monkeys are included in Order 

 Primates (pp. 220-221 ) ; elephants belong to Order Proboscidae (pp. 206- 

 207), whales to Order Cetacea, even-toed hoofed animals to Order Artio- 

 dactyla, odd-toed hoofed animals to Order Perissodactyla, and so on. 



Members of all orders just mentioned, and of some not mentioned, have 

 several characteristics in common. They have hair, they are warm-blooded, 

 the young develop in the uterus of the mother and then are bom (as con- 

 trasted with being hatched from eggs). Following birth the young are nour- 

 ished with milk secreted by mammary glands. Because of these and other 

 similarities the orders are grouped together into a larger category of classi- 

 fication called the class (Fig. 14.1 ). The particular class with which we are 

 concerned is Class Mammalia. Other classes are: Class Aves (birds), Class 



