CAN SCIENCE EXPLAIN LIFE? 



INTRODUCTION 



The various forms of life which are encoun- 

 tered in nature exhibit such a variety of appear- 

 ances and such a profusion of details that the 

 casual observer is often too bewildered by the 

 complexity of his surroundings to gain a clear 

 conception of life processes in their entirety and 

 to distinguish what is fundamental and indis- 

 pensable from what is superficial and unessential. 



Life is usually recognized by specific bodily 

 form, spontaneous mobility, and responsiveness 

 to stimuli, but these characteristics can all be 

 closely imitated artificially and in the lower forms 

 of life are often entirely absent, so that they must 

 be regarded as secondary characteristics which 

 have developed in the course of evolution and not 

 as primary attributes of life itself. 



Every living organism is unique in that it con- 

 stitutes an autonomous self-contained entity hav- 

 ing its own specific behavior, and which is capable, 

 under favorable conditions, of growing and pro- 

 ducing others like itself. The phenomena of 

 growth and reproduction are exhibited by every 

 living organism regardless of its rank in the plant 

 or animal kingdom and establish in nature a 



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