I had a discussion online with Ray Winstead who recently retired from the Indiana University of Pennsylvania in Biology. Ray has a page which I came across and found a diagram which is most compelling both for its biological meaning as well as the design (created by William Standaert):
The design is a flow model which receives energy in the form of sunlight and this energy undergoes a "food chain" transformation. The transformation begins with producers (e.g., plants) which are eaten by herbivores, which are in turn eaten by carnivores, to end the chain with the top carnivores (e.g., humans). There are actually 2 sub-chains in this diagram: one for consumers of live material, and the other for detritus. These types of models can be simulated: common model types used by ecologists include Odum graphs, System Dynamics, and compartmental models. Further information with a more abstract model can be found in the Wiki link on energy flow.