Cycling of materialsSpec 9.12
In short
Materials such as carbon, nitrogen and water are cycled through an ecosystem, moving between abiotic components (air, water and soil) and biotic components (living organisms). Plants build materials into biomass, which passes to animals when they feed. Decomposers break down dead organisms and waste, returning materials to be used again. Cycling is needed because supplies are limited.
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.
Written and checked against the Edexcel GCSE Biology (1BI0) specification · Updated October 2026
Frequently asked questions
How does carbon move through the carbon cycle?
Plants and algae take carbon dioxide from the air by photosynthesis and make carbon compounds, which pass along food chains when animals feed. All organisms release carbon dioxide by respiration. Decomposers break down dead organisms and waste and release carbon dioxide as they respire, and burning fuels releases carbon dioxide too.
What do decomposers do in an ecosystem?
Decomposers are microorganisms such as bacteria and fungi that release enzymes to break down dead plants, dead animals and waste. As they respire they release carbon dioxide into the air, and they also release mineral ions back into the soil. Without them, dead material would pile up and the materials in it could not be used again.
How does the nitrogen cycle work?
Decomposers break down proteins and urea in dead material and waste into ammonia. Nitrifying bacteria convert ammonium ions into nitrates, which plants absorb to make proteins. Nitrogen-fixing bacteria, in the soil or in legume root nodules, turn nitrogen gas into nitrogen compounds. Denitrifying bacteria turn nitrates back into nitrogen gas, reducing soil fertility.
All 5 questions on Material cycles
