SURVEY QUESTIONS 



Have you ever thought which factor was more important in your life, 

 heredity or environment? What does the farmer in your locality do to 

 increase the yield of his crops ? Do you know what is meant by artificial 

 selection? What are Mendel's laws ? What is meant by social inheritance ? 



Photo by Ewing Galloway 



UNIT XVIII 



THE IMPROVEMENT OF LIVING THINGS BY MAN 



Preview. As you look at the boys in your class, you notice that 

 each boy seems to be more or less like every other boy ; he has a 

 head, body, arms, and legs, and even in minor ways he resembles 

 each of the other boys in the room. Moreover, if you should ask 

 any particular boy, no doubt he would tell you that he resembled 

 in certain respects his mother or his father. If you should ask his 

 parents whom he resembled, they would say, " We can see traits 

 of his grandfather (or his grandmother) in him." 



The law of nature which causes a child to possess characters 

 like either or both of his parents, and like their parents as well, 



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