PROBLEM 3 Hcnv Ai'e Living Things Named and 



Classified? 



The variety of living things. If you and 



your classmates were to name all the 

 different kinds of living things that you 

 could remember you would probably 

 have a list with hundreds of names. Yet 

 as you know from reading Problems 

 I and 2 your list would represent only 

 a small part of the number of different 

 kinds of living things that biologists 

 know. Actually, more than one million 

 different kinds of living things have 

 been named and described by biologists. 



The need for classifying. In order that 

 anyone may have even a slight knowl- 

 edge of so many different kinds of plants 

 and animals they must be arranged in 

 groups. Then, by learning the groups in 

 which they are arranged a person can 

 have an understanding of one million 

 plants and animals without knowing the 

 names of more than a few hundred. 

 Such a grouping of a large number of 

 objects in an orderly way and according 

 to some definite arrangement is called 

 a classificatioji. You know that plants 

 and animals have been classified, for in 

 the earlier problems you learned some- 

 thing of this classification. Let us look 

 more closely into the methods of clas- 

 sifying. 



How all kinds of objects can be classi- 

 fied. If your hobby is collecting stamps, 

 you put together in one place in the 

 album all the stamps of one country; 



you classify your stamps by putting to- 

 gether those that are alike in some easily 

 recognizable \\'ay, some characteristic. 

 In classifying stamps the characteristic 

 in which the stamps in any group are 

 alike is that they were printed for the 

 same country. Coins, too, may be classi- 

 fied in this way. They may be grouped 

 as English, French, United States coins, 

 and so on. 



But if you have large numbers of coins 

 to take care of you do not stop when 

 you have grouped them according to 

 their countries. You find that the United 

 States coins are not all alike. Some may 

 be pennies, some nickels, and some dimes. 

 So you group them according to their 

 value. In other words, you now make a 

 further subdivision by using another 

 characteristic: the value of the coin. But 

 you can go still further in your classifi- 

 cation. You can subdivide the pennies, 

 for example, according to the date of 

 issue. You will find Exercises 1,2, and 3 

 useful for an understanding of classifi- 

 cation. 



By looking at the diagram of one coin 

 collection you will see that the first 

 groupings are few in number; there are 

 only three groups according to countrv^ 

 But when you come to the final group- 

 ing the groups are very numerous. Only 

 a few groups of the many possible ones 

 are shown in the diagram, Figure 126. 



