162 THE RELATIONS OF PLANTS TO ANIMALS 



directly upon plants, he eats the flesh of plant eating animals, 

 which in turn feed directly upon plants. And so it is the world 

 over ; the plants are the food makers and supply the animals. 



Ammonia 



Carbon dioxide 

 I (C0 2 ) 



"Water | Simple Salts 



Plants 



with chlorophyll 



buildup complex 



organic substances 



They store up 



energy from the sun 



in the process 



and 



Carbon dioxide 



| (C0 2 ) 



Animals 



and plants without 



chlorophyll 



Water 

 '(H 2 O) 



\ form / * ' \ . 



. (which tear down complexlAmmoma 



organic 



/food of \ rgamc substances / (NH 3 ) 

 and set free energy 



in the process in 

 form of heat 



\ 



/ | \ 



Energy from sun* 



The relations between green plants and animals. 



Energy set free 

 as heat. 



Green plants also give a very considerable amount of oxygen to 

 the atmosphere every day, which the animals may use. 



The Nitrogen Cycle. - The animals in their turn supply much 

 of the carbon dioxide that the plant uses in starch making. They 



also supply some of the 



ids etc 



nitrogenous matter used by 

 the plants, part being given 

 the plants from the dead 

 bodies of their own rela- 

 tives and part being pre- 

 pared from the nitrogen of 

 the air through the agency 

 of bacteria, which live 

 upon the roots of certain 

 plants. These bacteria are 

 the only organisms that 

 can take nitrogen from 

 the air. Thus, in spite of all the nitrogen of the atmosphere, 

 plants and animals are limited in the amount available. And the 



Nitrites 

 'Nitric Bacteria 



The nitrogen cycle. Trace the nitrogen from 

 its source in the air until it gets back again 

 into the air. 



