Mineral cycles may be generalized. The inorganic substances may be lost from the ecosystem into a SINK, where they are unavailable to organisms. The flow of energy drives the cycling of nutrients. Organisms use oxidation-reduction reactions to gain and transfer energy. Terrestrial biomes are defined by the dominant plant type.
Biomes are products of climates, soil types, chance, and history.
Biomes may intergrade or have sharp boundaries. This implies that the energy and materials in living systems must come from the non-living environment. This implies that every transformation of energy is accompanied by a loss of usable energy. The energy in living systems comes from the sun and is ultimately lost to space as infrared radiation. The system is open.