BIOLOGICAL ORDER 



Biological systems — that is, organisms — are endowed with genetic 

 continuity. 



The organism synthesizes its constitutive parts. Syntheses can take 

 place only if the system is provided with food and energy, which 

 are consumed in the processes involved; this is metabolism. When 

 provided with food, the organism metabolizes, grows, and re- 

 produces. The organism is the independent unit of reproduction. 



An organism is composed essentially of macromolecular com- 

 pounds, among which are nucleic acids and proteins. Even the 

 smallest organism contains a few thousand different species of 

 macromolecules. The simplest organism is therefore a relatively 

 complex machine. All know^n complex systems which contain 

 macromolecules and are able to reproduce their kind belong to the 

 living systems. Reproduction of a complex system containing macro- 

 molecules is therefore characteristic of life. And such a complex, 

 independent unit of integrated structures and functions that re- 

 produces true to type can only be an organism, a living organism. 



These statements might be considered too factual, and some 

 would perhaps prefer a more original and sophisticated definition. 

 The formulation which follows is an attempt at a summary of the 

 views expressed by Norbert Wiener, in his fascinating book 

 Cybernetics: "Living organisms are metastable Maxwell demons 

 whose stable state is to be dead." 



The Cell and Organisms 



Organisms belong to two categories: {a) the protists or microbes, 

 which are composed of one cell and are therefore the lower organ- 

 isms; (^) those which are composed of many cells, the so-called 

 higher organisms, the group to which we are so proud to belong. 



In 1857, Leydig described and defined the cell as a mass of 

 protoplasm containing a nucleus. This is an excellent definition. Let 

 us consider, for example, a microbial cell, a bacterium. It is a sphere 

 about 1 /i, in diameter. When properly handled and stained, it shows 

 a dark central body, the nucleus, surrounded by a pale substance 

 called cytoplasm. 



The cells of a multicellular organism are specialized, that is, 

 differentiated. The liver cells are different from the kidney cells 



[4] 



