Each step in the FOOD CHAIN contains appropriate numbers of organisms 
If one group becomes too numerous, the chain becomes UNBALANCED 
Each step in the FOOD CHAIN contains appropriate numbers of organisms 
For example, agricultural runoff creates a SURPLUS of nutrients which can cause sudden INCREASES in algae growth 
Each step in the FOOD CHAIN contains appropriate numbers of organisms 
Too much algae blocks sunlight from reaching vascular plants 
Each step in the FOOD CHAIN contains appropriate numbers of organisms 
Too few plants means LESS FOOD for herbivores