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Science · Grade 9

Energy in Living Systems

Learners explain ATP as the energy currency that links energy-releasing and energy-using processes, then model photosynthesis and cellular respiration with balanced equations, organelle locations and stages. They analyse limiting factors and the balance between photosynthesis and respiration with a growth model and gas-exchange data, and finish by tracking atoms and energy through plants, animals and decomposers, including where a tree's mass comes from.

  • 5 lessons
  • About 125 minutes
  • Energy in living systems check: 11 questions
  • Ways to answer: balance equations, fill in the blanks, choose an answer, draw a graph, highlight a text and label a picture
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What learners will discover

  • Explain how the ATP–ADP cycle transfers energy from respiration (and the light reactions) to cell processes, and why ATP is a currency rather than a store.
  • Model photosynthesis with a balanced equation, the chloroplast and its two stages, and use isotope and mass evidence to trace where its atoms come from.
  • Model aerobic respiration and fermentation with balanced equations, stages and locations, and compare their ATP yields quantitatively.
  • Interpret limiting factors and the balance between photosynthesis and respiration (net and gross rates, compensation point) using models and data, stating each model's limits.
  • Track matter and energy through photosynthesis and respiration, explaining why atoms cycle while energy flows through and leaves as heat.

Lessons

  1. ATP: the cell's energy currency 8 steps4 practiceabout 22 min
  2. Photosynthesis: capturing light 9 steps4 practiceabout 26 min
  3. Limiting factors and models of plant growth 8 steps4 practiceabout 26 min
  4. Cellular respiration: releasing energy 9 steps5 practiceabout 26 min
  5. Tracking matter and energy 8 steps5 practiceabout 25 min
  6. Energy in living systems check 11 questions at the end

Keep exploring

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Guide for grown-ups