Contrast net primary productivity with other pools and fluxes of biomass and energy. Describe energy transformations among trophic levels. V. Identify global patterns of NPP and the major factors determining these patterns. Purves et al. An ecosystem is all of the organisms and all the abiotic factors with which they interact.
Ecosystems are open.
Ecosystem boundaries are not discrete. The size of ecosystems can vary dramatically. Inputs and outputs of both of energy and nutrients exist. There is one way flow of energy through the ecosystem. Interacting components give rise to functional wholes.