CHAPTER XVIII 

 ADAPTATION OF ORGANISMS 



Every creature is a bundle of adaptations. Indeed, when 

 we take away the adaptations, what have we left? 



Thomson and Geddes. 



ORGANISMS are systems dependent for their maintenance 

 and operation upon energy liberated by chemico-physical 

 processes in protoplasm, and therefore any and all influences 

 which induce changes in the structure or functions of an 

 organism must initially modify the underlying phenomena 

 which are responsible therefor. In a word, organic response 

 is a problem of metabolism. Although it is highly important 

 that this cardinal fact be clearly grasped, the science of 

 biology to-day is not in a position to interpret the responses 

 of organisms in these fundamental terms, and we shall merely 

 present some representative instances to illustrate the fact 

 that the response of organisms, as exhibited in active adjust- 

 ment adaptation of internal and external relations, 

 overshadows in uniqueness all other characteristics of life 

 and at one stroke differentiates even the simplest organism 

 from the inorganic. 



Overwhelmingly striking as is the fitness of organisms to 

 their physical surroundings, we must not lose sight of the fact 

 that the environment itself presents a reciprocal fitness. This 

 results from the "unique or nearly unique properties of water, 

 carbonic acid, the compounds of carbon, hydrogen, and oxy- 

 gen. . . . No other environment consisting of primary con- 

 stituents made up of other known elements, or lacking water 



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