494 Organisms Are Products of 



back as the records go and was undoubt- 

 edly used before the dawn of written his- 

 tory. A description of the method used 

 with soybeans will make it clear. The 

 soybean is a plant that has long been cul- 

 tivated. You probably know that it has 

 many uses. It is excellent food for ani- 

 mals, either as fresh forage in the pasture 

 or when dried to make hay. The seeds 

 yield oil which may be used as food or in 

 many different commercial processes. 

 The seeds are also eaten by man because 

 of their large amounts of protein. 



Now the first step in breeding is to de- 

 termine the aim or goal; the breeder 

 must decide what kind of improvement 

 he wants to make in the plant or animal. 

 Let us suppose that the breeder wants to 



Heredity and Environment unit ix 



produce plants that have beans (seeds) 

 with larger oil content. He begins by 

 analyzing seeds from different plants to 

 discover which plants produce beans with 

 the largest oil content. He discards the 

 seeds from plants which produce little 

 oil. This is the process of selection or of 

 choosing the organisms that have the de- 

 sired character (large oil content). Then 

 he sows seeds of those plants which pro- 

 duce most oil. 



The plants that appear the next season 

 will probably produce beans with a 

 higher average oil content, since the 

 plants that produced little oil had been 

 discarded and were not used as parents. 

 Selecting the plants with the highest oil 

 content is then repeated. Since self- 



Fic. 441 (above) These few strawberry plants 

 were selected jrovi the whole field for breed- 

 ing. Why did the breeder destroy all the 

 others? (u. s. bureau of plant industry) 



Imc. 442 (left) Merino sheep have been bred 

 for their wool. This one sold for $13,425- '^^hy 

 such a high price? (journal of heredity) 



