308 CHARACTER OF OFFSPRING 



pupils of our school. Scientists distinguish, in a like manner, thou- 

 sands of individuals of one species of a plant or animal. These 



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Variations in the heads of birds. All the birds in 

 I the picture may be descendants of the same original 

 ancestor. Compare these with others that you know. 



are all enough alike to be classed as insects, pigeons, or dahlia 

 plants ; but each is different in some way from all the others. 



The problems of these likenesses and differences are the problems 

 of heredity. The study of heredity includes a study of all the 

 various characteristics in the offspring that are more or less similar 

 to those characters of the ancestors. 



Environment influencing development. Individuals of the 

 same species may differ because all do not have exactly the same 

 conditions during their early development. Differences in tem- 

 perature, in the relative amount of moisture, in the character of 

 weather, or of food may cause plants to be stunted or slow to 

 flower in one region when compared with the similar plants of 

 another region. A more abundant supply of mineral salts, or more 

 sunshine at certain periods, may produce plants that are some- 

 what better developed than others grown from the seeds of the 

 same parent plant. Every farm, every roadside, and every city lot 

 furnish examples of plants that have thrived better or worse than 

 their neighbors, because of variations in their environments. 



Temperature, moisture, light, and food are some of the factors 

 that influence the development of animals as well as of plants. 

 The male of the European bullfinch has a bright red breast ; the 

 female is entirely brown. If the male bird is fed on hempseed, its 

 plumage changes to a dull color similar to the female. Among honey- 



