The Carbon Cycle
What Is the Carbon Cycle?
The carbon cycle shows how carbon is recycled through living organisms and the environment.
💡 Key Concept: Carbon is a key element in all living things – it’s recycled so it can be used again and again.
Main Stages of the Carbon Cycle
1️ Photosynthesis
✔ Plants absorb carbon dioxide (CO₂) from the atmosphere and use it to make glucose during photosynthesis.
CO₂ + H₂O → Glucose + O₂CO₂ + H₂O → Glucose + O₂
2️ Feeding
✔ Animals eat plants, passing carbon compounds along the food chain.
3️ Respiration
✔ Plants, animals, and decomposers release CO₂ back into the air when they respire.
4️ Decomposition
✔ Microorganisms (decomposers) break down dead organisms and waste, releasing CO₂ through respiration.
5️ Combustion
✔ Burning fossil fuels or wood releases CO₂ into the atmosphere.
Other Pathways in the Carbon Cycle
✔ Some dead organisms form fossil fuels over millions of years.
✔ When burned, fossil fuels release stored carbon as CO₂.
✔ Carbon can also be stored short-term in oceans and as carbonates in rocks.
Human Impact on the Carbon Cycle
❌ Increased burning of fossil fuels adds more CO₂ than can be removed naturally.
❌ Deforestation reduces photosynthesis, so less CO₂ is absorbed.
✔ These contribute to global warming and climate change.
Key Processes and Their Roles
Process | Adds CO₂ to the Atmosphere? | Removes CO₂? |
Photosynthesis | ❌ | ✅ |
Respiration | ✅ | ❌ |
Combustion | ✅ | ❌ |
Decomposition | ✅ | ❌ |
Questions
- What process removes CO₂ from the atmosphere?
- How does respiration return carbon to the air?
- What happens when fossil fuels are burned?
- Why is decomposition important in the carbon cycle?
- Name one way humans affect the carbon cycle.
Summary
- The carbon cycle moves carbon through the biosphere, atmosphere, and geosphere.
- Photosynthesis removes CO₂; respiration, decomposition, and combustion add it.
- Human activities like deforestation and burning fossil fuels are disrupting the balance.
- The carbon cycle is essential for maintaining the Earth’s climate and life processes.