Description: Biosphere 2 was created in the 1990's to model all the elements of Biosphere 1 (The Earth). Plants in the biosphere produced oxygen and food for the inhabitants. The carbon dioxide released during respiration was taken in by the plants cycling the matter with energy from the Sun. In this experiment oxygen levels steadily fell to dangerous levels and oxygen eventually had to be added to the biosphere. This large-scale phenomenon continues to be owned and run by the University of Arizona. The mystery of missing oxygen could be used as a phenomenon in a unit on matter cycling and energy flow. Students can even create biospheres of their own and monitor life over time.
Web Resource: Biosphere 2 - Wikipedia