<p>We investigate the thermodynamics as well as the population dynamics of ecosystems based on a stochastic approach in which the biomasses of the several species of the ecosystem are treated as stochastic variables. The several species are connected by feeding relationships that are understood as unidirectional processes in which a certain amount of biomass is exchanged between species. We show that the equations for the averages in the biomass of species are those given by the deterministic approach. We determine the fluxes of mass, energy, and entropy as well as the rate of the entropy production. In the stationary state, the entropy production and the input of energy into the ecosystem are both found to be proportional to the organic mass generated by the autotrophs per unit time per unit mass of the autotrophs.</p>