Back to the lesson plan builder
Lesson length30 min45 min60 min
Questions🔀 New questions

Print the plan for yourself; the student sheet prints on its own page after it.

Science lesson plan · 10th grade (Year 11 in England) · 45 minutes

Decomposers, decay rates and recycling nutrients

Ecosystems and food chains

CCSS NGSS.HS-LS2-3CCSS NGSS.HS-LS2-5England: GCSE Combined Science: Ecology

Objective and success criteria

Students will: Decomposers, decay rates and recycling nutrients.

  • 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: Decomposers and recycling nutrients; The carbon cycle

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 (Decomposers and recycling nutrients; The carbon cycle). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Why are decomposers important for plants? (They give plants sunlight / They make plants grow faster in the dark / They eat plant pests only / They release nutrients (minerals) back into the soil) → They release nutrients (minerals) back into the soilPrompt: Where do plants get minerals from?
  2. Does this process remove carbon dioxide from the air or add it: decomposition by microorganisms? (removes CO₂ from the air / adds CO₂ to the air) → adds CO₂ to the airPrompt: Which process do green plants use to make glucose?
  3. Is a oak tree a producer, a consumer or a decomposer? (producer / consumer / decomposer) → producerPrompt: Does it make food, eat living things, or break down dead things?

Hook · 5 min

  • Show a food web and ask what would happen if one animal disappeared.
  • Share the objective: Decomposers, decay rates and recycling nutrients. 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: A bag of grass clippings had a mass of 200 g. After 10 days in a compost bin its mass was 180 g. What was the mean rate of decay, in g per day?
  • Step 1: 200 − 180 = 20 g
  • Step 2: 20 ÷ 10 = 2
  • Step 3: So the answer is: 2
  • Answer: 2
  • 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. A bag of grass clippings had a mass of 120 g. After 8 days in a compost bin its mass was 80 g. What was the mean rate of decay, in g per day? → 5Prompt: Find the mass lost.
  2. A biogas generator lets waste decay without oxygen. What useful gas does it produce? (oxygen / helium / methane, which can be burned as a fuel / nitrogen) → methane, which can be burned as a fuelPrompt: This gas is also the main part of natural gas.

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. A bag of grass clippings had a mass of 150 g. After 12 days in a compost bin its mass was 132 g. What was the mean rate of decay, in g per day? → 1.5Prompt: Find the mass lost.
  2. Decay: which statement is NOT true? (Decay returns mineral ions to the soil. / Compost can be used as a natural fertiliser. / Decay is fastest when everything is frozen. / Decay is faster when it is warm and moist.) → Decay is fastest when everything is frozen.Prompt: Does freezing speed decay up or slow it down?

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: Decomposers and recycling nutrients.
  • 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-10.

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

eurekami

Decomposers, decay rates and recycling nutrients

Name

Date

Score/ 8

  1. Question 1

    A bag of grass clippings had a mass of 100 g. After 12 days in a compost bin its mass was 64 g. What was the mean rate of decay, in g per day?

    Answer

  2. Question 2

    Food lasts longer in a fridge. Why?

    • A. Fridges add preservatives
    • B. Cold kills every microorganism
    • C. Low temperature slows the enzymes of decomposers
    • D. Fridges remove all water

  3. Question 3

    Decay: which statement is NOT true?

    • A. Decay returns mineral ions to the soil.
    • B. Decay is faster when it is warm and moist.
    • C. Decay is fastest when everything is frozen.
    • D. Compost can be used as a natural fertiliser.

  4. Question 4

    A bag of grass clippings had a mass of 150 g. After 20 days in a compost bin its mass was 50 g. What was the mean rate of decay, in g per day?

    Answer

  5. Question 5

    What role do decomposers play in the carbon cycle?

    • A. They lock carbon away forever
    • B. They turn carbon into oxygen
    • C. They photosynthesise
    • D. They respire, releasing carbon dioxide from dead material back into the air

  6. Question 6

    A bag of grass clippings had a mass of 150 g. After 12 days in a compost bin its mass was 102 g. What was the mean rate of decay, in g per day?

    Answer

  7. Question 7

    Why do gardeners turn their compost heaps regularly?

    • A. to dry it out completely
    • B. to kill all the microorganisms
    • C. to add oxygen for the decomposers' aerobic respiration
    • D. to cool the heap to 0 °C

  8. Question 8

    A bag of grass clippings had a mass of 150 g. After 5 days in a compost bin its mass was 135 g. What was the mean rate of decay, in g per day?

    Answer

Free from eurekami.com

for the adult only

Answer key: Decomposers, decay rates and recycling nutrients

  1. 1. 3

  2. 2. C. Low temperature slows the enzymes of decomposers

  3. 3. C. Decay is fastest when everything is frozen.

  4. 4. 5

  5. 5. D. They respire, releasing carbon dioxide from dead material back into the air

  6. 6. 4

  7. 7. C. to add oxygen for the decomposers' aerobic respiration

  8. 8. 3