Year 9 Science · AC9S9U03

Carbon cycle processes and Earth systems

Track carbon as matter moving among atmosphere, biosphere, hydrosphere and geosphere, then use the model to explain how changing transfer rates can alter carbon stores

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Key conceptTeach from the board

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.

Worked examplesWe do

Worked examples

AC9S9U03 - Carbon cycle processes and Earth systems
Example 1

Name one carbon store in each Earth sphere.

Example 2

Add a process label to an arrow from atmosphere to plant.

Example 3

Trace carbon from a plant to atmospheric CO₂ through two possible pathways.

Example 4

Explain how combustion changes the geosphere and atmosphere stores.

Curriculum examplesCopied content

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.

ComponentAC v9VictoriaNSW
Stores/transfers modelDirectDirectSupporting context
Human-impact reasoningDirectDirectStrong partial SC5-ENV-01
Questions and answersWith answers
  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.
Practice and reviewReady for practice
  • 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.
Curriculum alignmentStart here
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