526 



BIOLOGY FOR BEGINNERS 



Digestion 



Assimilation 



Excretion 



Oxidation and Life. In the process of photosynthesis, plants 

 accomplish the manufacture of organic food and tissue out of in- 

 organic materials, carbon dioxide, water, and mineral salts. 

 Plants are able to do this because, by means of their chlorophyll, 

 they can absorb energy from the sunlight sufficient to unite these 

 inorganic materials into complex organic substances. 



Animals cannot thus manufacture their own food, as they 

 do not possess chlorophyll. It is evident that they must depend 

 upon plants for all their organic food substances. Of course there 

 are animals who eat no plant foods, but they depend upon ani- 

 mals which do, so that in the end plants are the only food pro- 

 ducers. 



The chief function of food is to provide energy to support the 

 life of the consumer. This energy came from the sun, was locked 



