The general relationship between animal body weight, W, and population density, D, is D = A/W, where A is a constant (Peters, 1983). Highest packing of biomass depends only on the aggregate mass, not on the size of individual organisms. This means that it is biomass rather than population size that is maximized in an ecosystem, as density (number per unit area) is inversely proportional to the weight of the organisms. Of course, the relationship is complex. A given mass of mice would not contain the same exergy or number of individuals as an equivalent weight of elephants. Also, genome differences (Example 1) and other factors would figure in. Later, we will discuss exergy dissipation as an alternative objective function proposed for thermodynamic systems. If this were maximized rather than storage, then biomass packing would follow the relationship D = A/W0 65-0 75 (Peters, 1983). As this is not the case, biomass packing and the free energy associated with this lend general support for the exergy-storage hypothesis.
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