UNIT SEVEN 



Why Cannof Plants and Animals Live Forever? 



1 Are all plants and animals useful to man? 



2 Can a plant or animal be injurious to us in one way and useful in 



another way? 



3 Does an animal's instincts always make it behave in a way that is good 



for getting what it needs or for escaping danger or enemies? 



4 Do most plants and animals die a natural death? 



5 Is it possible for plants and animals to live without injury to other 



living things? 



6 Could a given region support more life if all animals ate only plants? 



7 What causes some pest or some disease to increase rapidly at certain 



times? 



8 What makes epidemics usually stop abruptly? 



9 Why has man been called the most destructive of living species? 



10 What happens in a region when native plants or animals are driven 

 out of it or exterminated? 



We can figure out a complete balance of chemical and physical forces in 

 organisms, like the balance of income and output of an engine. We feel never- 

 theless that "life" yields something over and above the chemical and physical 

 transformations of matter. As conscious beings, thinking of our pleasures and 

 satisfactions, of our plans and purposes, we wonder sometimes, "Why cannot 

 this go on forever?" Even in moments of suffering and sorrow or of disap- 

 pointment, we hope and reach out for better days. We cling to life and we 

 want more. Life is good. Why must it end? From what we observe in other 

 species, we assume that there is in all organisms a constant urge to keep on. 

 Presumably life is "worth living" wherever it is possible. But to the extent 

 that we are aware of life satisfactions, and especially of life possibilities, we are 

 puzzled and disturbed by the limitations. We recognize, of course, that in 

 nature nothing endures "forever". Natural objects are combinations of other 

 objects or bits. And these combinations are constantly being broken; the 

 parts are constantly being rearranged; the balance is constantly being upset. 

 Wherever anything is going on, any action whatever, all objects change; the 

 very mountains and the planets change. And to live means above all to do, to 

 rearrange. 



Life in general goes on, then. But individual plants and animals come and 

 go — some more quickly across the stage, some more slowly. And at any given 

 moment, in any particular spot, life goes on at all only as some individual 

 succumbs and yields its body to others as food or as raw material. And even- 



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