"Ecosystem: A Biotech Definition"

"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."

From "The Concise Biotech Dictionary" www.thebiotechdictionary.com/term/ecosystem

"Ecosystem: A Middle School Definition"

"Ecosystem - A grouping of plants, animals, water, air and land that are all dependent on each other for survival."

(Please note the minor typo correction - the word "are" was obviously missing between the words "that" and "all". Also, the word "animals" implicitly includes "humans" for the YESSS purposes of this definition.)

Since YESSS contest entries include the design and presentation of learning resources for younger students and their teachers, this is a good example of the word "ecosystem" as defined for Middle School Students (with thanks, to the folks circa 2006 at www.earthday.net and www.rprogress.org).

YESSS contestants are encouraged to check-in with their teachers and other mentors and also to use "ask.com", "wikipedia", "google", etc., to search for definitions of the word "Ecosystem".