The Carbon Cycle
Describe the carbon cycle, tracing carbon through photosynthesis, respiration, feeding, decomposition, and combustion, and explain the role of each process
What a learner can do afterwards
- Draws or labels a diagram of the carbon cycle showing the main processes
- Explains how photosynthesis removes carbon dioxide from the atmosphere
- Explains how respiration, combustion, and decomposition return carbon dioxide to the atmosphere
- Discusses how human activities (burning fossil fuels, deforestation) disrupt the carbon cycle
The lesson
Carbon never disappears. It just moves. It travels in a loop between the air, living things, and the ground called the carbon cycle. You already know plants pull carbon dioxide out of the air during photosynthesis. That is where most carbon enters living things.
Take a wooden table. That carbon was once carbon dioxide floating in the air. A tree absorbed it through photosynthesis and used the carbon to build sugar, then wood. When the tree was cut down, the carbon stayed locked in the wood, all the way to your table.
Burning coal, oil, and gas releases carbon that has been locked underground for millions of years. Cutting down forests removes trees that would pull CO2 back out of the air. Both add extra carbon to the atmosphere faster than the cycle can take it back.
Carbon keeps moving between air, living things, and the ground, and human activity is adding it to the air faster than the cycle can absorb it.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.