An ecosystem is the dynamic and interrelating complex of plant and animal communities and their associated non-living environment. The physical and climactic features and all the living and dead organisms in an area that are interrelated in the transfer of energy and material. An interacting complex of a community and its environment functioning as an ecological unit in nature. Differs from "system" in being a more rigorous definition that encompasses and requires assumptions of energetics, ecological interactions, species adaptations and so forth.