• 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 become rabbits / They stop eating seeds / 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… (predation / photosynthesis / decomposition / competition) → competitionPrompt: They both want the same limited resource.
3. Food webs: which statement is NOT true? (Removing a predator always helps every other species. / Animals often compete for food, water and space. / Removing one species can affect many others in a food web. / Plants compete for light, water and minerals.) → Removing a predator always helps every other species.Prompt: Think about what happens when one population changes.

• 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.

• 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.

• 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 100000 kJ of energy. About 10% of the energy passes to each next level. How much energy reaches the tertiary consumers, in kJ? → 100 kJPrompt: 10% means divide by 10 at each step.
2. A level of a food chain contains 4000 kJ. The next level gets 320 kJ. What is the percentage efficiency of the energy transfer? → 8 %Prompt: efficiency = energy passed on ÷ energy available × 100

• 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.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. 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? → 20 kJPrompt: 10% means divide by 10 at each step.
2. Why do food chains rarely have more than four or five levels? (Plants stop growing / There are not enough names for them / Top predators do not need energy / There is too little energy left to support more levels) → There is too little energy left to support more levelsPrompt: Think about how much is left after several 10% steps.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-7.