An ecosystem is a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life. Ecosystems contain biotic or living, parts, as well as abiotic factors, or nonliving parts. Biotic factors include plants, animals, and other organism .
The substance doesn't have a specific name. We just say that that substance is being reduced. Remember this mnemonic - OILRIG where "Oxidation is Loss, Reduction is Gain" of electrons.