basic laws which govern the behavior of 

 energy. The conceptual energese model 

 (fig. 6) illustrates the flow of energy 

 through an ecological system. Figure 7 

 applies this energese model to the naturally 

 occurring eelgrass community. Figure 8 fur- 

 ther illustrates the relationship between the 

 energy flow model and the natural system, 

 in this case the intertidal emergent wetland. 



Biogeochemicals— Elements and inorganic 

 compounds, many of which are essential 

 components for growth, circulate through 

 the biosphere (soil, water, and air) in 

 characteristic patterns known as biogeo- 

 chemical cycles (fig. 9). 



3. Abiotic factors— Essential environmental 

 factors which make life possible on the sur- 

 face of the earth are the constant inter- 

 actions of geologic, climatic, hydrologic, 

 and oceanographic changes. 



4. Biotic factors— The biotic world is classified 

 in respect to energy through trophic levels, 

 each of which is one exchange step beyond 

 the energy source which drives it (fig. 10). 

 Web diagrams will be used to depict trophic 

 levels and energy flows by using food webs 

 as examples. 



These concepts have been described by various , 

 prominent ecologists as being illustrative of the 

 interactions within a system. H. T. Odum (1966) 



Figure 6. Conceptual energy flow model. 



MkiohUI calMM 



Figure 7. Energy flow model of a natural eelgrass community. 



51 



