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Science lesson plan · 7th grade (Year 8 in England) · 30 minutes

Energy transfer and pyramids

Ecosystems and food chains

CCSS NGSS.MS-LS2-3CCSS NGSS.HS-LS2-4England: KS3 Biology: Interactions and interdependenciesEngland: KS4 Combined Science: Ecosystems

Objective and success criteria

Students will: Energy transfer and pyramids.

  • 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: Food webs and interdependence

Leads to: The carbon cycle; Calculate energy transfer efficiency between trophic levels

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 · 4 min

  • Quick retrieval from earlier learning (Food webs and interdependence). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Woodland food web: grass is eaten by rabbits and mice. Seeds are eaten by mice. Rabbits are eaten by foxes. Mice are eaten by foxes and owls. If disease killed most rabbits, what might happen to the mice? (They stop eating seeds / They become rabbits / They increase, because foxes stop eating / Their numbers fall, because foxes eat more mice) → Their numbers fall, because foxes eat more micePrompt: Foxes still need to eat.
  2. Rabbits and sheep both eat grass in the same field. This is an example of… (competition / predation / decomposition / photosynthesis) → competitionPrompt: They both want the same limited resource.
  3. Food webs: which statement is NOT true? (Predator and prey populations often rise and fall in cycles. / Plants do not compete with each other. / Animals often compete for food, water and space. / Plants compete for light, water and minerals.) → Plants do not compete with each other.Prompt: Think about what happens when one population changes.

Hook · 3 min

  • Show a food web and ask what would happen if one animal disappeared.
  • Share the objective: Energy transfer and pyramids. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Producers in a field capture 20000 kJ of energy. About 10% of the energy passes to each next level. How much energy reaches the tertiary consumers, in kJ?
  • Step 1: 20000 ÷ 1000 = 20
  • Step 2: So the answer is: 20 kJ
  • Answer: 20 kJ
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 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 capture 50000 kJ of energy. About 10% of the energy passes to each next level. How much energy reaches the tertiary consumers, in kJ? → 50 kJPrompt: 10% means divide by 10 at each step.
  2. A level of a food chain contains 8000 kJ. The next level gets 1600 kJ. What is the percentage efficiency of the energy transfer? → 20 %Prompt: efficiency = energy passed on ÷ energy available × 100

You do: independent practice · 7 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 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  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 tertiary consumers, in kJ? → 10 kJPrompt: 10% means divide by 10 at each step.
  2. A level of a food chain contains 2000 kJ. The next level gets 100 kJ. What is the percentage efficiency of the energy transfer? → 5 %Prompt: efficiency = energy passed on ÷ energy available × 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: Food webs and interdependence.
  • 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

  • Move on to: The carbon cycle; Calculate energy transfer efficiency between trophic levels.
  • 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-7.

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

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Energy transfer and pyramids

Name

Date

Score/ 6

  1. Question 1

    Producers in a field capture 100000 kJ of energy. About 10% of the energy passes to each next level. How much energy reaches the tertiary consumers, in kJ?

    AnswerkJ

  2. Question 2

    A level of a food chain contains 8000 kJ. The next level gets 1200 kJ. What is the percentage efficiency of the energy transfer?

    Answer%

  3. Question 3

    Why is only about 10% of energy passed to the next level of a food chain?

    • A. Plants keep all the energy
    • B. Animals refuse to eat most of their food
    • C. Energy is destroyed at each level
    • D. Much is used for respiration and movement, or lost as heat and waste

  4. Question 4

    Producers in a field capture 20000 kJ of energy. About 10% of the energy passes to each next level. How much energy reaches the primary consumers, in kJ?

    AnswerkJ

  5. Question 5

    A level of a food chain contains 4000 kJ. The next level gets 480 kJ. What is the percentage efficiency of the energy transfer?

    Answer%

  6. Question 6

    Why do food chains rarely have more than four or five levels?

    • A. There is too little energy left to support more levels
    • B. There are not enough names for them
    • C. Plants stop growing
    • D. Top predators do not need energy

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Answer key: Energy transfer and pyramids

  1. 1. 100 kJ

  2. 2. 15 %

  3. 3. D. Much is used for respiration and movement, or lost as heat and waste

  4. 4. 2000 kJ

  5. 5. 12 %

  6. 6. A. There is too little energy left to support more levels