4 BIOLOGY AND HUMAN LIFE 



bodies life is present only under certain conditions, which in- 

 clude electricity, chemical energy, heat, and others. But we 

 cannot think of life by itself. It means nothing to us except the 

 way living things behave— what plants and animals do. 



3. How biology is used. Many plants and animals have 

 a bearing upon human life. A little reflection will show that 

 whatever we can do about living things we can do more 



Fig. I. Fossil remains of plant life 



The plants that left these impressions in the rocks at Florissant, on the western side 



of Pikes Peak in Colorado, lived a million years ago or more. (From photograph 



furnished by the American Museum of Natural History) 



effectively or usefully if we have a better understanding of life. 

 In the case of our useful plants and animals, biology can teach 

 us how to increase their numbers, how to protect them from 

 their enemies or disease, and also how to improve their qualities. 

 In the case of our own bodies, biology teaches us substantially 

 all we know about preserving health and about curing disease. 

 It is applied biology that has made it possible, since the Civil 

 War, to add over ten years to the average length of life of people 



