Consider an ecosystem consisting of three trophic levels, 1 being the lowest and 3 the top predator level. Let the system be described by a set of differential equations, each representing the biomass dynamics of one of the three levels. The model is within the basic framework introduced by May and co-workers ; represents biomasses of the trophic level.[more]
A biologically consistent system is obtained with non-negative parameter values. The corner solution reduces the system to just the lowest trophic level (1), while and , , , and positive defines a system of three distinct levels, where levels 1 and 3 only interact through level 2.
Initial biomass levels are indicated in the graph by a red point, while corresponding terminal values are found at the green point. The connecting blue curve is the time path of the biomass development within the three trophic levels between these two points. The three bars give a graphical representation of the terminal biomasses of the three levels.[less]
 R. May, J. R. Beddington, C. W. Clark, S. J. Holt, and R. M. Laws, "Management of Multispecies Fisheries," Science, 205, 1979 pp. 267–277.