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Science lesson plan · 12th grade (Year 13 in England) · 45 minutes

Calculate energy transfer efficiency between trophic levels

Ecosystems and food chains

CCSS NGSS.HS-LS2-4CCSS NGSS.SEP 5England: GCSE Biology: Ecology (trophic levels and biomass)

Objective and success criteria

Students will: Calculate energy transfer efficiency between trophic levels.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Energy transfer and pyramids

Leads to: the next skill in this area.

Materials: Food web cards, Arrows to build chains, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 5 min

  • Quick retrieval from earlier learning (Energy transfer and pyramids). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Producers in a field capture 50000 kJ of energy. About 10% of the energy passes to each next level. How much energy reaches the primary consumers, in kJ? → 5000 kJPrompt: 10% means divide by 10 at each step.
  2. A level of a food chain contains 8000 kJ. The next level gets 800 kJ. What is the percentage efficiency of the energy transfer? → 10 %Prompt: efficiency = energy passed on ÷ energy available × 100
  3. A pyramid of biomass shows… (the mass of living material at each level / the temperature at each level / the number of species in the world / the height of the animals) → the mass of living material at each levelPrompt: "Bio" means life, "mass" means…

Hook · 5 min

  • Show a food web and ask what would happen if one animal disappeared.
  • Share the objective: Calculate energy transfer efficiency between trophic levels. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Producers in a field store 50000 kJ/m² of energy per year. Primary consumers gain 2500 kJ/m². What is the efficiency of energy transfer, in %?
  • Step 1: 2500 ÷ 50000 × 100 = 5
  • Step 2: So the answer is: 5 %
  • Answer: 5 %
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. Producers in a field store 20000 kJ/m² of energy per year. Primary consumers gain 2400 kJ/m². What is the efficiency of energy transfer, in %? → 12 %Prompt: efficiency = energy transferred to the next level ÷ energy in the level below × 100
  2. Producers capture 200000 kJ. 20 % is passed to primary consumers and 5 % of that is passed to secondary consumers. How much energy reaches the secondary consumers, in kJ? → 2000 kJPrompt: Do one step at a time.

You do: independent practice · 10 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Why are food chains rarely longer than 4 or 5 levels? (Animals refuse to eat higher animals / Plants stop growing / Too little energy is left to support another level / There are not enough species on Earth) → Too little energy is left to support another levelPrompt: About 90 % is lost at each step.
  2. Producers in a field store 40000 kJ/m² of energy per year. Primary consumers gain 4800 kJ/m². What is the efficiency of energy transfer, in %? → 12 %Prompt: efficiency = energy transferred to the next level ÷ energy in the level below × 100

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Energy transfer and pyramids.
  • Use concrete materials: food web cards.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-12.

Free lesson plan from eurekami.com/lesson-plan-builder

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Calculate energy transfer efficiency between trophic levels

Name

Date

Score/ 8

  1. Question 1

    Producers capture 200000 kJ. 20 % is passed to primary consumers and 10 % of that is passed to secondary consumers. How much energy reaches the secondary consumers, in kJ?

    AnswerkJ

  2. Question 2

    Why is energy transfer between trophic levels inefficient?

    • A. Consumers photosynthesise
    • B. Much is used in respiration and lost as heat, and some material is not eaten or digested
    • C. Predators eat too much
    • D. Energy is destroyed at each level

  3. Question 3

    Producers in a field store 25000 kJ/m² of energy per year. Primary consumers gain 1250 kJ/m². What is the efficiency of energy transfer, in %?

    Answer%

  4. Question 4

    Producers capture 500000 kJ. 10 % is passed to primary consumers and 5 % of that is passed to secondary consumers. How much energy reaches the secondary consumers, in kJ?

    AnswerkJ

  5. Question 5

    Why are food chains rarely longer than 4 or 5 levels?

    • A. Too little energy is left to support another level
    • B. Plants stop growing
    • C. Animals refuse to eat higher animals
    • D. There are not enough species on Earth

  6. Question 6

    Producers in a field store 40000 kJ/m² of energy per year. Primary consumers gain 8000 kJ/m². What is the efficiency of energy transfer, in %?

    Answer%

  7. Question 7

    Producers capture 200000 kJ. 20 % is passed to primary consumers and 5 % of that is passed to secondary consumers. How much energy reaches the secondary consumers, in kJ?

    AnswerkJ

  8. Question 8

    Producers in a field store 20000 kJ/m² of energy per year. Primary consumers gain 2000 kJ/m². What is the efficiency of energy transfer, in %?

    Answer%

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Answer key: Calculate energy transfer efficiency between trophic levels

  1. 1. 4000 kJ

  2. 2. B. Much is used in respiration and lost as heat, and some material is not eaten or digested

  3. 3. 5 %

  4. 4. 2500 kJ

  5. 5. A. Too little energy is left to support another level

  6. 6. 20 %

  7. 7. 2000 kJ

  8. 8. 10 %