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Science

Nutrient Cycles

Overview

Students trace the movement of carbon atoms through the environment, discovering that the same atoms are recycled over and over through living and non-living systems.

Learning Objective
Students understand how carbon and nitrogen cycle through ecosystems and why decomposition is essential for life.

Resources needed

  • None

Lesson stages

0 / 7 done
  1. 1 Ask: where did the carbon in your body come from? (The food you ate, which came from plants, which came from CO2 in the air).
  2. 2 Introduce the carbon cycle: carbon moves between atmosphere, living things, oceans, and rocks.
  3. 3 Trace the cycle: photosynthesis removes CO2 from air, stored in plants, eaten by animals, released by respiration, returned to atmosphere.
  4. 4 Introduce decomposition: bacteria and fungi break down dead organisms, returning carbon to soil and atmosphere.
  5. 5 Ask: what is burning fossil fuels doing to the carbon cycle? (Releasing ancient stored carbon rapidly).
  6. 6 Briefly introduce the nitrogen cycle: nitrogen gas fixed by bacteria, into amino acids in plants, eaten, decomposed, returned to atmosphere.
  7. 7 Ask: why would an ecosystem collapse without decomposers?

Tap a step to mark it as done.

Variations

  • Observe decomposition: bury a leaf in soil and check after two weeks.
  • Compare the carbon stored in different systems: living plants, soil, ocean, atmosphere, fossil fuels.
  • Discuss how humans disrupt nitrogen cycles through fertiliser runoff.
More information

Teach: cycle, decompose, respiration, photosynthesis, atmosphere, fossil fuel, nitrogen fixation. The phrase the same atoms recycled is the most important conceptual anchor.

Focus on the carbon cycle only before introducing nitrogen.

Can students trace carbon from the atmosphere into a plant, then an animal, then back to the atmosphere? Can they explain why decomposers are essential?

No resources needed. Observing decomposition uses only a leaf and soil.

Students often think decomposition is a purely negative process. In ecosystems, decomposition is essential — it returns nutrients to the soil, without which plant growth would eventually cease.

Nutrient cycles connect ecology, chemistry, and Earth science.

Activity details
Secondary Medium 25 minutes no prep Whole Class, Small Group Indoor & Outdoor
Topics
Nutrient Cycles Carbon Cycle Decomposition