308 Nutrients 



population, not merely the individuals most recently added to the 

 population. For a replenishment of certain critical nutrients the chief 

 source is the dead bodies of the animals and plants themselves. The 

 presence of other sets of organisms— the decomposers and transform- 

 ers—is required to convert the organic materials to forms suitable for 

 the growth of green plants, and frequently physical agents are neces- 

 sary to restore the nutrients to zones where growth can take place 

 once more. 



