250 LIVING THINGS IN THEIR ENVIRONMENT 



can think of hundreds of ways in which living things re- 

 spond to stimuli. Roots grow towards water, leaves and 



stems turn to the light, 

 earthworms seek dark- 

 ness, and moths fly 

 toward a bright light. 

 All the forces of the 

 environment influence 

 us and we make re- 

 sponses. See how 

 many of your own 

 daily acts are actual 

 responses to stimuli. 

 Think of a pickle and 

 see what happens. Do 

 you know why your 

 mouth watered ? Ask 

 your teacher to ex- 

 plain or read about it 

 in some physiology. 



Did you ever think 

 of the many kinds of 

 living things every- 

 where around us ? Life is everywhere birds and in- 

 sects in the air, fish and frogs in the water, animals and 

 plants on the land, and even in the soil. A careful sur- 

 vey of a square foot of earth will show it teeming with life, 

 most of it microscopic. You also must have wondered 

 why certain plants and animals are found living in swamps 

 or ponds, while others, quite different, are found in the 

 woods or fields. Why do we find polar bears and seals in 

 the arctic regions and lions and tigers in the tropics? 

 Why is it that there are no trees on the tops of the moun- 

 tains and plenty of trees further down the slopes ? Why 

 is it that the desert plants and animals differ so greatly 



Wright Pierce 



This plant was photographed after having been 



placed in bright sunlight for six hours. Are 



green plants sensitive 7 



