320 Cell as Basis of Organic Activity 



broken, air containing microorganisms was able to pass into the flask 

 and the broth fermented. In 1870, T. H. Huxley was able to say "Liv- 

 ing matter always arises by the agency of pre-existing living matter." 

 This he termed "biogenesis." 



Though life as we know it today does not arise from nonliving ma- 

 terial, it is not static ; rather it is constantly changing and adjusting to 

 meet the demands of a harsh environment. This process of gradual 

 change which has resulted in the multitude of animal and plant forms 

 is termed evolution. 



The principle of organic evolution was clearly stated by Darwin 

 in his book The Origin of Species which was published in 1859. Since 

 the time of Darwin, it has been demonstrated again and again that living 

 materials are continuously, though imperceptibly, changing. It is now 

 recognized that this great principle of gradual change also applies to the 

 development of civilizations, the growth of the individual — in fact to 

 all living phenomena. As such, this concept becomes one of the great 

 unifying principles of biology. 



THE ORIGINS OF LIFE 



While Redi and Pasteur decisively demonstrated that living materials 

 can arise only from previously existing ones, clearly at some time in the 

 past life must have originated from some nonliving system. While the 

 precise nature of the first living organism will never be known, one can 

 speculate. With the increased knowledge of physical and chemical 

 phenomena, a more factual basis can be given to these speculations. 



Certainly before life could come into existence, a long period of 

 chemical evolution was necessary. Conceivably at some remote period, 

 the earth was a formless, reactive mass of material. Perhaps from this 

 amorphous matter, the chemical compounds arose through purely chance 

 combinations of electrons. Obviously this can at present not be proved. 



Once the simple compounds had formed, it must be assumed that 

 innumerable chemical reactions were taking place. Somewhere in all 

 this reactive mass, proteins of a very simple type were formed. These 

 may have arisen from such a material as ammonia which could have 

 been present in abundant quantities. Most important of all is the fact 

 that these compounds were rich in available energy which was tied into 

 chemical bonds. Perhaps the first organism could not synthesize the 

 complicated proteins and phosphates that are so necessary for modern 



