All of those regions of earth's waters, crust, and atmosphere in which organisms can exist.

An ecological test project, a "planet in a bottle", and a structure originally built to be a man-made, materially-closed ecological system located in Oracle, Arizona, United States.

Under a sealed glass and metal dome, different habitats were recreated, with representatives of nearly 4,000 species, to test the effects that various environmental factors have on ecosystems.

Simulated ecosystems, or "mesocosms", include savanna, desert, rain forest, marsh, and Caribbean reef.

The response of such systems to elevated atmospheric concentrations of carbon dioxide gas are among the priorities of Biosphere 2 researchers.

As of June 5, 2007, the property of Biosphere 2, including surrounding land, totaling 1,650 acres (6.7 km²), sold to a residential home developer for US $50 million.

A development including homes and a resort hotel was planned for a portion of the land. The Biosphere itself remains open for tours.

On June 26, 2007, the University of Arizona announced it would take over research at Biosphere 2. The announcement ended immediate fears that the famous glass vivarium would be demolished.

University officials said private gifts and grants enabled them to cover research and operating costs for three years with the possibility of extending that funding for 10 years.