Biologists Study Anivials a?id Plants 



do not yet know how these types of 

 penicilhn differ or what the chemical 

 make-up of penicilhn is. By the time 

 you read this it is likely that much more 

 will be known about this spectacular 

 drug. 



The problem of cancer is of tremen- 

 dous interest to men and women. How 

 can we detect it as soon as it starts so 

 that we can save a human life? What 

 causes it? Do we know exactly how 

 such organs as the liver and the spleen 

 function in man? How do vitamins act 

 to prevent certain diseases? Is "intelli- 

 gence" — whatever it is — inherited? If 

 so, how? If not, what produces it? What 

 can we do to improve it in boys and 

 girls? What makes us act as we do? 



And basic to all these questions: What 

 kind of material is the living stuff in all 

 plants and animals? Will we ever be 

 able to make such living stuff in the 

 laboratory? 



There are thousands of such questions 

 that can be asked, and, fortunately, there 

 are thousands of men and women in 

 every country trying to answer them. 



The most fascinating part of the study 

 of biology is that at any moment a com- 

 plete or a partial answer to a problem 

 may be provided. When you read this 

 book you may know the answer to a 

 question that the authors did not know 

 when they wrote it. The pursuit of 

 biological knowledge goes on always 

 with continuing success. 



In UNIT I you "will consider these problems: 



Problem i . \\^hat Kinds of Animals Inhabit the Earth? 

 Problem 2. What Kinds of Plants Inhabit the Earth? 

 Problem 3. How Are Living Things Named and Classified? 



