Source 



The circular symbol represents a source of energy such as the sun, fossil 

 fuel, or the water from a reservoir. Circular symbols can also represent 

 forcing functions such as tides, geologic events, and climatology. 



Primary The bullet-shaped symbol represents the reception of pure wave energy 



Producer such as sound, light, and water waves. In this module, energy interacts 



with some cycling material producing an energy-activated state, which 

 then returns to its deactivated state,passing energy on to the next step 

 in a chain of processes. Green plants, which capture the sun's energy 

 to build carbohydrates from the earth's elements, are an example. 



Storage The passive storage symbol shows location in a system for passive 



Compartment storage, such as moving potatoes into a grocery store or fuel into a tank. 

 No new potential energy is generated, and some work must be done in 

 the process of moving the potential energy in and out of the storage by 

 some other unit. 



Consumer The hexagonal symbol represents the combination of storage compart- 



ment and work gate by which potential energy stored in one or more 

 sites in a subsystem is fed back to do work on the successful processing 

 and work of that unit. Autotrophic animals or consumers are repre- 

 sented by this symbol. 



■J2 



Detrital 



Microbial 



Complex 



Work 

 Gate 



This symbol is a combination of a storage compartment and a consumer 

 compartment. The storage compartment refers to detrital particles, 

 dead pieces of organic material which contain stored energy. The 

 microbial decomposers colonize on the detrital particles and consume 

 the stored energy within the particles for their own growth and main- 

 tenance. 



The work gate module at which a flow of energy (J 2) makes possible 

 another flow of energy Uj). This action may be as simple as a person 

 turning a valve, or it may be the interaction of limiting fertilizer in 

 photosynthesis. 



r igure 1-7. An explanation of the symbols used in the energy flow model 

 (figure 1-6) . 



(continued) 



1-11 



10-80 



