The Carbon Cycle
Lesson notes
Overview
Carbon moves between atmosphere, living things, oceans and rocks. This topic is rated advanced and is number 52 of 110 in Biology. Deeper models, formal results and harder reasoning.
What you are seeing
The panel above shows the steps of a process, laid out in order. Click a step to see what happens next. The animation is drawn live from the model, so everything you see responds to the sliders. Press Space to pause, use Restart to replay from the start, and change the speed to slow down quick events.
In depth
Carbon moves between the atmosphere, living things, oceans, soils and rocks. Plants and algae take CO₂ in by photosynthesis, animals eat them, and respiration, decay and burning return it to the air. Over millions of years carbon is stored as limestone and fossil fuels. Burning those fuels releases it faster than natural processes can absorb it, so atmospheric CO₂ has risen about 50% since the industrial revolution, driving climate change.
Reading the relationship
The expression "CO₂ ⇄ organic carbon" is a compact summary of the idea. It uses the symbols C, O₂, o, r, g, a; name what each one stands for before you start. Then use the sliders to see how changing one quantity changes the others.
A guided exploration
1. Run the animation once with the default settings and describe in words what happens. 2. Change one slider at a time and note which quantity responds most. 3. Push each slider to its extreme and decide whether the result still makes sense.
Try this
Try to explain why the pattern holds, not just what it is. Look for limiting cases and what happens at the edges.
Common pitfalls
Biological processes are rarely all-or-nothing. Look for the feedback, the timing and the exceptions, rather than learning a single fixed sequence by heart.
How it connects
It builds on “The Ecological Energy Pyramid”, the topic before it in Biology. Once you are comfortable, continue with “The Nitrogen Cycle”.
Why it matters
Biology shows how living things are built and how they work, grow, inherit traits and adapt.
Where you might use it
- Revising “The Carbon Cycle” before a class, exam or certification
- Understanding inherited conditions, medicines and how the body responds to disease
- Working in farming, conservation and food production, where populations and genes matter
- Following news about vaccines, genetic testing and climate effects on wildlife
Frequently asked questions
What is The Carbon Cycle?
Carbon moves between atmosphere, living things, oceans and rocks. It is an advanced topic in Biology.
How do I use the The Carbon Cycle simulation?
The panel at the top shows the steps of a process, laid out in order. Click a step to see what happens next. Move the sliders one at a time, then press Space to pause the animation and look closer.
What does the formula mean?
The expression CO₂ ⇄ organic carbon packs the idea into symbols. Name each symbol first, then change one quantity with the sliders and see which others respond.
Who is this topic for?
Deeper models, formal results and harder reasoning. If the quiz feels hard, reread the lesson notes and try the previous topic first.
What should I learn before this?
Start with “The Ecological Energy Pyramid”, the previous topic in Biology. Each topic in a subject builds on the ones before it.
How do I track my progress?
Press “Mark as learned” on this page. Progress is stored only in this browser and is never sent anywhere. The Browse page can show topics you have learned or still need to learn.