Cycling of materialsSpec 9.12
Materials such as carbon, nitrogen and water are cycled through an ecosystem, moving between the abiotic components (air, water and soil) and the biotic components (living organisms).
Plants take up materials from the air, water and soil and build them into their own biomass. The materials pass to animals when they feed. Materials return to the soil and air when organisms excrete waste, and when dead organisms and their waste are broken down by decomposers. The materials can then be used again by new organisms. Cycling is needed because the supply of each material is limited.