We present an extremely minimal ecosystem model which takes account of thermodynamic constraints on the organisms’ metabolism. This suggests a way to test the application of a hypothesised principle of Maximum Entropy Production to ecosystems. It also puts definite physical bounds on the rates at which matter can flow through the system and paves the way for more detailed models that have thermodynamic principles built in from the start. In providing the background for this model we point out some connections between thermodynamic principles and autopoiesis.