Unity and Interdependence in Living World 649 



ties than you at first surmised. These many similarities among living 

 organisms reveal a certain close relationship, which in turn proves a 

 certain degree of unity or uniformity among all living organisms. If a 

 study of the entire animal or plant kingdom were to be made, and the 

 similarities of the various species noted, one would have to conclude 

 that there is a certain degree of unity in the animal and plant kingdoms. 



C. Unity and Cooperation Between Various Types of Living Organ- 

 isms 



As we look about us in the living world and note the great struggles, 

 animosities, battles, and antagonisms, it is difficult to realize that there 

 are many, if any, instances in which there is real cooperation. However, 

 a little investigation will reveal that this is true. In spite of all the 

 struggles in the living v/orld, none of them arc so great as to disrupt life 

 in any great region or cause any great catastrophes. After all, there 

 must be, and is, more unity and harmony than discord among living 

 organisms or they would quickly exterminate each other, which would 

 result in ultimate and widespread ruin. In spite of the many hatreds 

 and struggles throughout the living world, there are many attempts at 

 cooperation, which in the final analysis seems to be a clue to a successful 

 living and accomplishment. When will man with all his powers and 

 abilities learn this one fact and place it into actual use? It is quite true 

 that a certain amount of struggle and competition is necessary to bring 

 out and develop the best in organisms, but these carried too far and 

 made unnecessarily vicious tend to hinder development and progress 

 and may ultim.ately lead to destruction. How does this link up with 

 the condition of mankind over the world today? Is there not a great 

 lesson to be learned from this great biologic principle in the conduct of 

 human affairs? 



When one studies the living organisms as a group, there is apparent 

 a great degree of unity and cooperation not only between members of 

 the same species, but also among members of different species. In fact, 

 this spirit of cooperation exists not only between animals of diflferent 

 species but between various species of animals and a great variety of 

 plants. Undoubtedly, there are many examples of the latter phenome- 

 non, but none will better illustrate the point than the so-called cycles in 

 Nature. The following typical cycles (Fig. 325) will be considered: 

 nitrogen, carbon, and oxygen cycles. 



1 . Nitrogen Cycle. — Nitrogen is one of the essential elements of which 

 living protoplasm is composed, being particularly essential in the con- 



