INTRODUCTION 



TO 



BIOLOGY 



Life 



Biology is, by etymology, the study of life. Life is 

 difficult to define, and the easiest solution is to decide, as so many 

 people have done, that its definition is impossible. In his book The 

 Nature of Life, Szent-Gyorgyi writes: "Life as such does not exist; 

 nobody has ever seen it. . . . The noun 'life' has no sense, there 

 being no such thing." Yet, it is well known that definition is among 

 the methods for discovery. It is, as a matter of fact, an excellent 

 heuristic method. For it obliges one to condense the essential of a 

 category or of a phenomenon into a formula — the formula con- 

 taining everything it has to contain, and excluding everything it 

 has to exclude. To cast a good definition is therefore useful, for 

 this exercise compels critical consideration of all the terms or aspects 

 of a problem. 



Life may be considered either as a property, or as a mamfestatio7i, 

 or as a state of organisms. This might or might not satisfy the 

 biologist. The physicist will immediately ask two questions: (1) 

 What is an organism? (2) What is the specific property^ of living 

 organisms that does not exist in the inanimate world and is therefore 

 characteristic of life? 



The Organism 



An organism may be visualized as a complex, organized, specific 

 system able to reproduce its kind. An organism never appears de 

 novo but always derives from a pre-existing, identical organism. 



[3] 



