Figure 1: Schematic distribution of chemical energy in a simple model ecosystem is described by an energy level diagram. The governing thermodynamic principle is exemplified by considering only one type of base constituents (atoms), but the result has been generalized for diverse base constituents [35]. The number of individuals at trophic level j makes a population . The corresponding density-in-energy amounts from the number of base constituents that are needed to assemble the population and from the invested energy . For a species at a level j in the food web many atoms and much energy are needed to propel its growth and to maintain it in the mature state. Species are equipped with mechanisms to generate these vital flows of energy by numerous reactions (arrows) that absorb high-energy or emit low-energy quanta (wavy arrows). Systems on larger areas, hence having access to more base constituents , will evolve to larger and more effective energy transduction machineries comprising more species. Coloring emphasizes that species differ from each other by their energy transduction properties, that is, phenotypes.