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Science lesson plan · 12th grade (Year 13 in England) · 60 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 · 6 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 10000 kJ of energy. About 10% of the energy passes to each next level. How much energy reaches the secondary consumers, in kJ? → 100 kJPrompt: 10% means divide by 10 at each step.
  2. A level of a food chain contains 5000 kJ. The next level gets 1000 kJ. What is the percentage efficiency of the energy transfer? → 20 %Prompt: efficiency = energy passed on ÷ energy available × 100
  3. Why do food chains rarely have more than four or five levels? (There is too little energy left to support more levels / Plants stop growing / Top predators do not need energy / There are not enough names for them) → There is too little energy left to support more levelsPrompt: Think about how much is left after several 10% steps.

Hook · 6 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 · 12 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 · 12 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 25000 kJ/m² of energy per year. Primary consumers gain 2500 kJ/m². What is the efficiency of energy transfer, in %? → 10 %Prompt: efficiency = energy transferred to the next level ÷ energy in the level below × 100
  2. Producers capture 500000 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? → 5000 kJPrompt: Do one step at a time.

You do: independent practice · 17 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 · 7 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Producers capture 200000 kJ. 10 % is passed to primary consumers and 10 % of that is passed to secondary consumers. How much energy reaches the secondary consumers, in kJ? → 2000 kJPrompt: Do one step at a time.
  2. Producers in a field store 20000 kJ/m² of energy per year. Primary consumers gain 3000 kJ/m². What is the efficiency of energy transfer, in %? → 15 %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

    Why is eating plant foods often more energy-efficient for feeding people than eating meat?

    • A. Animals photosynthesise
    • B. Fewer trophic levels means less energy is lost before it reaches people
    • C. Plants contain no energy
    • D. Meat contains no protein

  2. Question 2

    Producers in a field store 10000 kJ/m² of energy per year. Primary consumers gain 1500 kJ/m². What is the efficiency of energy transfer, in %?

    Answer%

  3. Question 3

    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

  4. Question 4

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

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

  5. Question 5

    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%

  6. Question 6

    Producers capture 1000000 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

  7. Question 7

    Producers in a field store 50000 kJ/m² of energy per year. Primary consumers gain 6000 kJ/m². What is the efficiency of energy transfer, in %?

    Answer%

  8. Question 8

    Producers capture 500000 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

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Answer key: Calculate energy transfer efficiency between trophic levels

  1. 1. B. Fewer trophic levels means less energy is lost before it reaches people

  2. 2. 15 %

  3. 3. 2000 kJ

  4. 4. C. Too little energy is left to support another level

  5. 5. 20 %

  6. 6. 10000 kJ

  7. 7. 12 %

  8. 8. 5000 kJ