Carbon cycle processes and Earth systems — AC9S9U03

• Identify major carbon stores in all four Earth spheres.
• Name processes that transfer carbon, including photosynthesis, respiration, decomposition, combustion and ocean exchange.
• Trace a carbon atom through several stores without treating the cycle as one fixed loop.
• Predict consequences when human activity changes a carbon transfer rate.

Recall photosynthesis and respiration at a word-equation level, food chains, combustion, and the atmosphere, biosphere, hydrosphere and geosphere. Distinguish matter from energy.

A store is where carbon is held; a transfer is the process moving it. Carbon dioxide in air is an atmospheric store; living biomass is biospheric; dissolved carbon is hydrospheric; carbonate rock and fossil carbon are geospheric stores.

Photosynthesis transfers carbon from atmospheric CO₂ into biomass. Respiration and decomposition return carbon to the atmosphere or water. Combustion rapidly transfers carbon in fuels/biomass to atmospheric CO₂. Oceans exchange carbon with the atmosphere, and geological processes act over much longer timescales.

The carbon cycle is a network, not a simple circle. Different pathways operate at different rates. Carbon atoms are rearranged into different substances; they are not created by combustion.

• Combustion creates carbon. Carbon atoms were already in the fuel.
• The carbon cycle is one circular route. It is a network with several stores and pathways.
• All pathways operate at the same rate. Biological, oceanic and geological processes span very different timescales.
• Energy cycles like carbon. Matter cycles; energy flows and is transferred.

1. Name one carbon store in each Earth sphere.
2. Add a process label to an arrow from atmosphere to plant.
3. Trace carbon from a plant to atmospheric CO₂ through two possible pathways.
4. Explain how combustion changes the geosphere and atmosphere stores.

1. Distinguish a carbon store from a carbon transfer.
2. Explain roles of photosynthesis and respiration in opposite carbon transfers.
3. Trace carbon through atmosphere → plant → animal → atmosphere.
4. Explain one route by which carbon can enter the hydrosphere.
5. Predict how reduced forest biomass may affect at least two carbon stores.
6. Evaluate a diagram that shows carbon arrows but no process labels.

A region experiences extensive forest clearing and increased fossil-fuel use at the same time. Build a cause-and-effect explanation for likely changes to carbon transfers and stores. Identify which parts are direct consequences and which would require measured evidence to quantify.

1. Where is carbon stored? In atmospheric gases, living/dead biomass, water and dissolved carbon, soils, sediments, rocks and fossil carbon.
2. What does photosynthesis do to carbon? It transfers carbon from CO₂ into organic molecules in producers.
3. Why is combustion important? It can rapidly transfer stored carbon to atmospheric CO₂.
4. Why is the cycle a network? Carbon can move among several stores by multiple pathways operating at different rates.

1. Draw and explain a carbon pathway containing at least three Earth spheres.
   Label every arrow with a process, not only a direction.
2. Explain how photosynthesis, respiration and combustion interact in the carbon cycle.
   State which store loses carbon and which gains it for each process.
3. Predict how a sustained increase in combustion could alter carbon stores and explain why the change does not violate conservation of matter.
   Track existing carbon atoms; do not say carbon is created.

• I can name four Earth-sphere carbon stores.
• I can label transfer processes correctly.
• I can trace carbon through a network.
• I can reason about a changed transfer rate.

Exit ticket: Trace one carbon atom from atmospheric CO₂ into a plant and back to the atmosphere by two different pathways.

Australian Curriculum v9.0 — AC9S9U03: carbon-cycle representation and interactions among Earth’s spheres.

Victoria Levels 9–10 — VC2S10U10: Exact direct carbon-cycle/Earth-systems relationship.

NSW Stage 5 — SC5-ENV-01: Partial strong relationship through analysis of human impacts on the natural world, without claiming a one-code carbon-cycle equivalent.

• AC9S9U05 — energy systems
• AC9S9H04 — research priorities
• AC9S9I05 — analyse patterns

• Australian Curriculum v9.0
• Victorian Curriculum F–10 Version 2.0
• NSW Science 7–10 Syllabus (2023)

Curriculum equivalents for Represent the carbon cycle and examine how key processes including...

Mapped skill: represent the carbon cycle and examine how key processes including combustion, photosynthesis and respiration rely on interactions between Earth’s spheres (the geosphere, biosphere, hydrosphere and atmosphere)

These references identify matching or closely related learning. Curriculum sequence, terminology and depth vary, so teachers should use the mapped skill and lesson difficulty to confirm suitability.

Australian Curriculum v9.0 is the canonical source for this SkillrHub lesson. Victoria and NSW entries name the closest published state codes or outcomes; international entries are planning references rather than claims of identical curricula.