ORIGIN OF LIFE IN THE OCEANS 125 



evolution of organisms, metabolism, a characteristic of living 

 matter, then became more complicated and was improved. 

 Through natural selection, intermediate systems with imperfectly 

 organized metabolism disappeared from the earth, A comparative 

 study of the metabolism in the most primitive organisms still in 

 existence make it possible to judge the way in which the newer 

 extremely efficient order of chemical reactions so characteristic of 

 the more recently developed higher animals and plants gradually 

 evolved. 



From studies in comparative biochemistry, it clearly appears 

 that some metabolic systems arose early and are typical of all 

 organisms without any exceptions. Others, on the contrary, 

 developed much later as additions to structures already in exist- 

 ence. The capacity for organic, heterotrophic nutrition or the 

 utilization of ready-made organic substances as building materials 

 together with an energy source is the most primitive form of 

 metabolic organization. It is innate in the structure of living matter 

 and inherent in all living organisms without exception. The first 

 organisms were doubtless heterotrophs. Such studies also show 

 convincingly that these were in addition anaerobes, as it is an 

 anaerobic metabolism which provides energy for all organisms. 

 This is quite understandable in view of the fact that both the 

 primeval atmosphere and hydrosphere had reducing charac- 

 teristics. 



In the development of life, the supply of abiogenetically formed 

 organic substances on the earth's surface gradually became 

 exhausted, because the development of life proceeded more rapidly 

 than did the formation of these substances. This change in the 

 conditions for existence increased the importance of those organ- 

 isms which on account of their ability to absorb light could 

 synthesize organic substances from inorganic carbon compounds 

 or from carbon dioxide in the atmosphere. In this way photo- 

 synthesis, a new biological method for the formation of organic 

 substances, replaced the earlier inefficient and slow abiogenetic 

 formation of such substances. This occurred because photosyn- 

 thesis came to dominate and monopolize the metabolic process, a 

 situation which has been efficient until the present day. 



The emergence of photosynthesis altered all life on the earth. 



