GENERAL ZOOLOGY 



Summary 



The genes located in the chromosomes of the nucleus have been found to be 

 responsible for all types of similarities between individuals related by 

 descent, from gross morphological characteristics to single enzyme-directed 

 metabolic reactions. In fact, insofar as we know, everything that a living 

 cell does can be referred in the final analysis to genie initiation and direction. 

 If these amazing self-perpetuating units were immutable, it may be supposed 

 that all living organisms would be identical within narrow limits, reflecting 

 environmental influence on genie expression. A great common pool of genes 

 is obviously present in living organisms as evidenced by the many similarities 

 that exist in the reactions of all cells. But innumerable changes have occurred 

 through the ages that living things have existed on the earth. You will be- 

 come acquainted with the great diversity of animal life as you continue your 

 study of zoology. The capacity of genes to become changed and to per- 

 petuate that change has provided the material from which the environment 

 has selected during the process of organic evolution. Not only is the past 

 and present status of living organisms conditioned by the genes they carry, 

 but their future potentialities are latent in the possibilities for change in 

 the genome. Is it any wonder that many scientists work with all the resources 

 at their command to determine the nature of the gene? 



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