Who this is for: Cambridge IGCSE Biology (0610) students who mix up the carbon and nitrogen cycles, forget the role of decomposers, or cannot name the processes that return nutrients to the soil.
What query it owns: how to understand and revise nutrient cycles in Cambridge IGCSE Biology.
Why this is safe: this page owns the nutrient-cycles revision-guide angle, while Tutopiya’s Nutrient Cycles subtopic page owns the learning resource and the free Nutrient Cycles quiz owns the practice.

Nutrient cycles describe how elements such as carbon, nitrogen and water move between living organisms, the atmosphere, soil and water. Cambridge IGCSE Biology (0610) tests whether you can describe each process, name the organisms involved, and explain why recycling matters for ecosystems. This guide covers the syllabus definitions, cycle diagrams, and the question types that appear every year.

Key takeaways

• Nutrients are recycled; energy flows through ecosystems and is lost as heat.
• Decomposers (bacteria, fungi) break down dead material and return minerals to the soil.
• The carbon cycle links photosynthesis, respiration, combustion and decomposition.
• The nitrogen cycle involves fixation, nitrification, assimilation and denitrification.
• Nitrates are taken up by plant roots for protein synthesis.

What are nutrient cycles in Cambridge IGCSE Biology?

Nutrient cycles are the pathways by which chemical elements move between biotic and abiotic components of an ecosystem. Carbon cycles through photosynthesis and respiration; nitrogen cycles through bacterial processes in soil; water cycles through evaporation, transpiration and precipitation. You can read the full explanation, worked examples and notes on Tutopiya’s Nutrient Cycles subtopic page before you attempt questions.

The core ideas you must master

Idea	What it means	How the exam uses it
Recycling	Nutrients reused; not lost from Earth	”Explain why nutrients are recycled”
Decomposer	Breaks down dead organic matter	”State the role of fungi in a cycle”
Photosynthesis	Removes CO₂ from air; builds organic compounds	”Name a process in the carbon cycle”
Respiration	Releases CO₂; returns carbon to atmosphere	”Describe how carbon returns to the air”
Nitrogen fixation	N₂ → usable nitrogen compounds	”Name bacteria that fix nitrogen”

Carbon cycle — key processes

Process	What happens	Organism / location
Photosynthesis	CO₂ → glucose	Plants, algae
Respiration	Glucose → CO₂ + energy	All living organisms
Decomposition	Dead matter → CO₂ + minerals	Decomposers in soil
Combustion	Fuel burns → CO₂	Human activity (fossil fuels)
Feeding	Carbon moves between trophic levels	Consumers eating producers

Nitrogen cycle — key stages (overview)

Stage	Process	Key organisms
Fixation	N₂ gas → ammonia / nitrates	Nitrogen-fixing bacteria (root nodules, soil)
Nitrification	Ammonia → nitrites → nitrates	Nitrifying bacteria
Assimilation	Plants absorb nitrates; animals eat plants	Plants, consumers
Denitrification	Nitrates → N₂ gas	Denitrifying bacteria
Decomposition	Proteins in dead matter → ammonia	Decomposers

For flashcard-level recall of nitrogen stages, use the Nitrogen Cycle flashcard deck.

Nutrient cycles in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical nutrient-cycle stem
Describe	Step-by-step process	”Describe the carbon cycle.”
Name	Identify organism or process	”Name a process that adds CO₂ to the atmosphere.”
Explain	Cause and effect	”Explain the role of decomposers in nutrient cycling.”
State	Short factual answer	”State how plants obtain nitrogen.”
Complete	Fill gaps in a diagram	”Complete the nitrogen cycle diagram.”

Worked exam-style stems (how to answer the wording)

1. “Name two processes that add carbon dioxide to the atmosphere.” Any two from: respiration, decomposition, combustion. Mark-scheme reward: named processes, not vague “animals breathe”.
2. “Explain the role of decomposers in the nitrogen cycle.” Decomposers break down proteins in dead organisms → release ammonia → nitrifying bacteria convert to nitrates → plants absorb nitrates. Reward: linked chain with named stages.
3. “State the difference between energy flow and nutrient cycling.” Energy flows through ecosystems and is lost as heat at each trophic level; nutrients are recycled between organisms and the environment. Reward: both ideas in one answer.

When you can recognise the wording instantly, work the full set on the Organisms and their Environment topical past paper questions and the Nutrient Cycles quiz.

How nutrient cycles connect to the rest of the syllabus

Nutrient cycles link to Food Chains and Food Webs (decomposers at the end of chains) and Energy Flow (energy vs nutrient distinction). The Cambridge IGCSE Biology resource hub links every Organisms and their Environment subtopic.

Common mistakes students make

• Confusing energy flow (one-way, lost as heat) with nutrient recycling (cyclical).
• Omitting combustion as a carbon-cycle process.
• Saying plants absorb nitrogen gas directly (they absorb nitrates from soil).
• Forgetting denitrification returns nitrogen to the atmosphere.
• Drawing cycle arrows without naming the process at each step.

When you need more support

If nutrient-cycle diagrams keep costing marks — especially nitrogen stages — work through the Organisms and their Environment topical past paper questions, the Nitrogen Cycle flashcards and the Nutrient Cycles quiz, then get focused help from a Cambridge IGCSE Biology tutor.

Frequently asked questions

Is the nitrogen cycle hard in Cambridge IGCSE Biology? It has more stages than the carbon cycle, but marks come from naming processes and organisms in order — flashcards help.

What is the role of decomposers in nutrient cycles? They break down dead organic matter and release minerals (and CO₂) back into the environment for reuse.

Do plants use nitrogen gas from the air? Not directly — they absorb nitrates from the soil; only nitrogen-fixing bacteria convert N₂ gas into usable compounds.

How do I revise nutrient cycles effectively? Draw labelled carbon and nitrogen cycles from memory, name bacteria at each stage, then take the Nutrient Cycles quiz.

Ready to master Cambridge IGCSE Biology nutrient cycles?

Start with the Nutrient Cycles subtopic page, then book a free trial with a Cambridge IGCSE Biology specialist to turn cycle diagrams into guaranteed marks.

Ready to Excel in Your Studies?

Get personalised help from Tutopiya's expert tutors. Whether it's IGCSE, IB, A-Levels, or any other curriculum — we match you with the perfect tutor and your first session is free.

Book Your Free Trial