IMPROVEMENT OF PLANTS AND ANIMALS 



FIG. 4. Heights of a thousand men arranged in order. The great majority 

 differ by small amounts. There are a few giants and a few dwarfs 



tendency to vary may be said to be one of the characters 

 that is inherited. 



9. Natural Selection. There is room in the world for 

 only a small proportion of the plants and animals that 

 begin life. A single corn plant usually has five hun- 

 dred to a thousand kernels. If all were planted and 

 grew, the entire world would soon be a corn-field. A 

 morning-glory plant may produce several thousand seeds. 

 A puff-ball produces millions of spores, each of which is 

 ready to grow if given proper conditions. Since the total 

 number of plants cannot greatly increase, it is evident 

 that only a few of the hundreds or thousands of seeds 

 produced by one plant can grow. All the others must be 

 crowded out. If a thousand plants come up where there 

 is room for but one, the strong will overshadow the weak 



3 10 13 ZQ 85 30 33 -*O *3 Ao 55 



FIG. 5. Egg production of 65 hens for one year. The number varied from 

 none to 170 



