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is called heredity. If we consider our own individual cases, we shall 

 probably find that we resemble our ancestors not only in physical 

 characters but also in mental qualities. The ability to play the 

 piano well or to paint well may be as much a case of inheritance as 

 the color of one's eyes or the shape of one's nose. We are a complex 

 of physical and mental characters, received from all our ancestors. 



But no boy in the class is exactly like any other boy; even 

 brothers are different in appearance and in action. Each one of us 

 tends to be slightly different from his or her parents. Each plant, 

 each animal, varies in a small degree from its immediate ancestors, 

 and it may vary to a great degree. This tendency among plants 

 and animals to be different from their ancestors and from each other 

 is called variation. Heredity and variation are the corner stones 

 on which all the work in the improvement of plants and animals, 

 including man himself, is built. 



Charles Darwin was one of the first scientists to suggest how the 

 laws of heredity apply to the development of plants and animals. 

 He knew that although animals and plants are like their ancestors, 

 they also tend to vary. In nature, he believed, the variations 

 which best fit a plant or animal for life in its own environment are 

 the ones which are handed down, because those individuals having 

 variations not fitted for fife in that particular environment will die. 

 Thus, said Darwin, since favorable variations survive and repro- 

 duce, and, as the descendants of each of these individuals also 

 tend to vary slightly, a new type of plant or animal, fitted for that 

 special place, is gradually formed. Darwin reasoned that if favor- 

 able variants are developed in nature, then man, by selecting the 

 variations he wanted, could form new varieties of plants and 

 animals much more quickly than nature. When we compare the 

 improved breeds of dogs with the original wild dog, or cultivated 

 fruits like the apple and peach with their wild ancestors, no one 

 can doubt that man has done much in the way of improving do- 

 mesticated plants and animals. 



Every farmer knows that to produce good results he must first 

 have good seed or good stock. The plants or animals must come 

 from sturdy parents. Then they must have favorable conditions 

 in which to grow, or they will not produce. They must have care. 



