GENERAL BIOLOGY 



CHAPTER I. 

 INTERDEPENDENCE OF ORGANISMS 



The primary demand of individual livelihood is for food. 

 Getting a living is the first business of life, and food is the 

 basis of a living; for the body derives both its substance 

 and its energy from its food. 



The gathering of the food for the living world is mainly 

 the work of green plants. These derive carbon from the 

 air and mineral matters from the soil, and build them up 

 into living substance, clothing the earth with verdure and 

 storing up food materials that make animal life possible. 

 Green plants constitute in themselves by far the greater 

 part of the living substance that is in the earth, and support 

 other forms of life out of the excess of their product over 

 what is necessary to maintain their own growth and 

 reproduction. 



The primary food of animals is plants and plant products. 

 Animals consume a small part of living plants, a much 

 larger part of plant products (fruits, tubers, wood, etc.) 

 and nearly the whole of plant remains. They use this 

 plant material for building their own bodies and supplying 

 their energy, and excrete it again as simple mineral com- 

 pounds. Thus they rapidly restore to the soil plant food 

 materials which might otherwise remain long locked up in 

 the bodies of dead plants. Thus the world's available 

 supply of food material is kept in circulation; and thus, green 

 plants and animals are complemental, each preparing food 

 for the other. 



That so large a part of living vegetation escapes being 

 eaten is due to the fact that animals, primarily herbivorous, 



