Ecosphere

An ecosphere ia a world in miniature, a tiny slice of life sealed off from the outside world. It could be described as an ecosystem in a bottle. Materially closed, but thermodynamically open, it takes no additional material from the outside but still alows heat and sunlight in.
Ideally, an ecosphere is self-statining. Once sealed, the animals and plants contained in it should be able to survive indefinitely, by cyclimg carbon, nitrogen, oxygen and other elements.