ENVIRONMENT OF PLANTS AND ANIMALS 21 



SULPHUR 



PHOSPHORU5I 

 CALCIUM 



NITROGEN 

 3.7s Iks. 



0.031U %,o% 

 SiGXts. y-jir 



HYDROGEN 



I3.65\bs. 



9.1^ 



CARBON 



13.5^ 



OXYGEN 



I08.l5lb5. 



in the environment, for example, water, food, the air, and the soil. 

 It is logical to believe that living things use the chemical elements 

 in their surroundings and in some won- 

 derful manner build up their own bodies 

 from the materials found in their en- 

 vironment. How this is done we will 

 learn in later chapters. 



What Plants and Animals take from 

 their Environment. Air. — It is a self- 

 evident fact that animals need air. 

 Even those living in the water use the 

 air dissolved in the water. A fish 

 placed in an air-tight jar will soon die. 

 It will be proven later that plants also 

 need air in order to live. 



Water. — We all know that water 

 must form part of the environment of 

 plants and animals. It is a matter of 

 common knowledge that pets need 

 water to drink; so do other animals. 

 Every one knows we must water a 

 potted plant if we expect it to grow. 

 Water is of so much importance to man 

 that from the time of the Caesars until 

 now he has spent enormous sums of money to bring pure water 

 to his cities. The United States government is spending millions 

 of dollars at the present time to bring by irrigation the water 

 needed to support life in the western desert lands. 



Light as Condition of the Environment. — Light is another im- 

 portant factor of the environment. A study of the leaves on any 

 green plant growing near a window will convince one that such 

 plants grow toward the light. All green plants are thus influenced 

 by the sun. Other plants which are not green seem either indif- 

 ferent or are negatively influenced (move away from) the source 

 of light. Animals may or may not be attracted by light. A 

 moth, for example, will fly toward a flame, an earthworm will 

 move away from light. Some animals prefer a moderate or 



<f^ 



Chart to show the percentage 

 of chemical elements in the 

 human body. 



