PART IX. MAN'S CONTROL OF HIS ENVIRONMENT 



IN RELATION TO IMPROVEMENT OF PLANTS 



AND ANIMALS 



CHAPTER XXXI 

 PLANT AND ANIMAL BREEDING 



Problems: To determine what makes the offspring of animals or 

 of plants tend to he like their parents. 



To determine what makes the offspring of animals or of plants 

 differ from their parents. 



To learn about some methods of plant and animal breeding. 



(a) By selection. 



(b) By hybridizing. 



(c) By other methods. 



Suggestions for Laboratory Work 



Laboratory exercise. On variation and heredity among members of ii 

 class in the schoolroom. 



Laboratory exercise. On the construction of a curve of variation in measure- 

 ments from given plants or animals. 



Laboratory demonstration. Stained egg cells (ascaris) to show chromosomes. 



Laboratory demonstrations. To illustrate the part played in plant and 

 animal breeding by (a) selection ; (b) hybridizing ; (c) budding and grafting. 



Heredity and what it means. — 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 his grandfather (or his grandmother) 

 in him." 



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