486 Organisms Are Products of Heredity and E?wiron?nent unit ix 



Fig. 434 These hogs are of the same age. The one on the left was raised on clean 

 gronnd; the other was raised on grotmd infected by parasitic worms. Of what impor- 

 tance is the enviromnent? Might there be another reason for the difference between 

 the hogs? (u. s. department of agriculture) 





Fig. 4^5 Two plants of the comino7i evening primrose, grown tinder iiorinal con- 

 ditions, are shown on the left. The single plant on the right received fewer hours 

 (otily 10) of daylight each day. What effects did this have on the plant? Why can you 

 not draw conclusions front this picture alone about the effect of light on plants? 

 What other information would you need? (journal agricultural research) 



