Many controversial debates (including conferences, symposia and of of the same) are generated by misunderstanding of the concepts or, often, by associating wrong terms to the same concept. The sustainability science or the ecologic theory (more exactly, the theory on the ecological systems) is an (intellectual) crucial pillar to handle the current and future challenges regarding the non-anthropic and artefactual environment. The paper aims to put a (whatever small) brick to clarify the grounding concept of the ecological system, in order to prevent its inflationary and un-rigorous use in research and public policy. The basic contributions are: (a) identifying the sufficiency predicates to logically define the concept of ecological system, (b) the suggestion to approach the issue from a mix evolutionary perspective based on Lamarckian-Darwinian theories; (c) some opinions regarding the scientific utility of using such a clear, on logical bases, concept of ecological system (given the general concept of system).