medium difficulty5 min

Carbon Cycle

The carbon cycle is the movement of carbon among the atmosphere, living organisms, oceans, soil, rocks, and fossil fuels through processes such as photosynthesis, respiration, decomposition, and combustion.

In one line: Plants take carbon in; breathing, decay, and burning send it back.

Practice This Concept

Understand it

Plants take carbon dioxide from air during photosynthesis and make food.
Animals get carbon by eating plants or other animals.
Respiration and decomposition return carbon dioxide to the atmosphere.
Burning fuels also releases carbon dioxide, so human activity can increase atmospheric carbon.

Example

A tree absorbs carbon dioxide during photosynthesis, a deer eats leaves, and both plants and animals release carbon dioxide during respiration.

Rule to remember

Rule: photosynthesis removes carbon dioxide from air; respiration, decomposition, and combustion return carbon dioxide to air.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

When coal is burned in a power plant, carbon stored underground for a long time combines with oxygen and is released as carbon dioxide, adding carbon to the atmosphere.

Method you can reuse

Identify the carbon reservoir, name the process moving carbon, state the direction of movement, and mention its effect on atmospheric carbon dioxide.

Sketch it in your answer

Draw arrows from atmospheric carbon dioxide to plants by photosynthesis, plants to animals by feeding, and arrows back to atmosphere by respiration, decomposition, and combustion.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

How does photosynthesis help in the carbon cycle?

Think first, then show answer

Photosynthesis helps the carbon cycle by removing carbon dioxide from the atmosphere and converting carbon into food molecules in plants.

Common wrong answer

Only animals add carbon dioxide to air.

Why it loses marks: Plants also respire, decomposers release carbon dioxide, and combustion adds carbon dioxide.

Don't mix this up

Students often mention photosynthesis but forget respiration, decomposition, and combustion as pathways returning carbon to the atmosphere.

Exam tip

For carbon-cycle answers, write reservoirs and processes: atmosphere, plants, animals, soil, oceans, photosynthesis, respiration, decomposition, and combustion.

Carbon Cycle diagram

Open full screen to read every label clearly.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Questions may ask how carbon dioxide is removed from air and how it returns through living and non-living processes.

1
Enough for 1 mark
The carbon cycle is the movement of carbon among the atmosphere, living organisms, oceans, soil, rocks, and fossil fuels through processes such as photosynthesis, respiration, decomposition, and combustion.
2
Add for 2 marks
Example: A tree absorbs carbon dioxide during photosynthesis, a deer eats leaves, and both plants and animals release carbon dioxide during respiration.
3
Add for 3 marks
Plants take carbon dioxide from air during photosynthesis and make food.

MCQ Quiz

Practice this concept with focused MCQs

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