126 



HISTORY OF THE OCEANS 



It created an abundance of organic substances and at the same 

 time led to the appearance of free gaseous oxygen. This had 

 hitherto been lacking on the earth's surface. It changed the 

 character of the chemical processes and enabled most living 

 organisms to change the energy source used in metabolism, to 

 develop new systems for oxygen respiration, and thus to utilize 

 completely the energy to be derived from organic substances. 



With the appearance of photosynthesis, the evolution of both 

 plants and animals proceeded at an ever increasing rate as shown 

 by paleontological data. If we now try to view the whole history 

 of evolution, at a glance, from the moment our planet was formed 

 until the present, we shall see that with each new step in its 

 development the rate of development increased rapidly. The 

 general development proceeds with time as if on an exponential 

 curve turning steeply upward (Fig. 1). During most of its existence 

 our planet was devoid of life. The abiogenetic evolution of organic 

 substances took some billions of years. With the origin of life, the 

 development proceeded much more rapidly. The drastic biological 

 changes took only some hundreds or even scores of millions of 

 years. The formation and biological development of man took 

 only a million years. Finally, social changes occurred in the course 



emergence 

 of man 



emergence 

 of We 



k 5 



years 



