Exercises XII and XIII 



THE ARRAY OF LIVING ORGANISMS 59 



TABLE 2 



are called phyla; from these one works down 

 through smaller and smaller divisions, finally to 

 the double name, genus and species, by which 

 any single type of organism is called. 



Some idea of the task involved in classifying 

 and naming living organisms may be gained 

 from the realization that there are about 300,000 

 living plant and over a million animal species. 

 It is a little like assigning a meaningful status 

 and relationships to everyone in Los Angeles. 



The main taxonomic divisions can best be 

 illustrated by classifying a few familiar organ- 

 isms from the three kingdoms, as we have done 

 in Table 2. How much of this kind of thing do 

 we want you to know? We want you to know 

 the really important things that are involved in 

 and lie behind such classification schemes. We 

 will try to point them out to you as we go along, 

 and they are summarized in the diagrams which 

 follow. 



A depressing thing about much of the tech- 

 nical terminology used in classification is that 

 it keeps changing. Even at any given time, we 

 find great disagreement involving even the main 

 categories. For example, the terms "Trache- 

 ophyta" and "Pteropsida" used in the classifica- 

 tion of corn in Table 2 are characterized as 

 "abandoned" by a recent authority (H. C. Bold, 

 The Plant Kingdom, Prentice-Hall, 1960). In- 

 deed, what are eight plant phyla in Simpson, 

 et ai, have now been reclassified by Bold into 

 24 "divisions." 



What saves this situation from its zealots are 

 two things: common names, which do stay in 

 use; and the possibility of expressing most of 



the fundamental relationships in plain English. 

 Thus in place of the above technical classifica- 

 tion of corn, already obsolete according to some 

 authorities, we can describe it safely as a vascu- 

 lar, flowering, seed plant, one of the grasses — 

 indeed, Indian corn or maize. 



Another point important for us is that we 

 classify only to the extent that serves our needs. 

 For example, most biologists would say of 

 Paramecium that it is a protozoan and a ciliate, 

 and let it go at that. As for the lobster, most of 

 us are content to know that among the Arthro- 

 pods it is a decapod crustacean. For the most 

 part, the remaining terms used in Table 2 would 

 be used only by specialists. 



So relax, use common names and ordinary 

 English as much as you like, but do learn to 

 recognize the important groups of protists, ani- 

 mals, and plants, and learn as much as you can 

 of the relationships among them. Read your 

 text, and use the following pages as a guide to 

 what we most want you to learn. 



THE PROTISTS 

 Guidelines 



(1) Close relations between bacteria and blue- 

 green algae as structurally simplest pro- 

 tists. 



(2) The "flagellate line." 



(3) Colonial algae as first approaches to dif- 

 ferentiated multicellular organisms. 



