THE CHANGING WORLD OF LIFE 



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tion. Also, there can be changes in the chromosomes themselves. Stud- 

 ies of genetics have shown us ways in which evolution can take place. 

 High energy radiation not only increases the rate of mutation, but also 



Photos by Winchester 



Fig. 34.12. Fossil remains enable us to trace the development of animal life in the 

 past. Top, a mosasaur that lived about 80 million years ago, found in Kansas. Center, 

 a ground sloth only partly excavated, found in Bolivia. It lived about a million years 

 ago. Bottom, a fossil fish that lived about 45 million years ago, found in the Green 



River slate in Wyoming. 



