• 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. Bees are declining. Why could this affect fruit farmers? (Bees eat fruit / Fruit trees need honey to grow / Bees make the rain / Fewer flowers would be pollinated, so less fruit forms) → Fewer flowers would be pollinated, so less fruit formsPrompt: What do bees carry between flowers?
3. Food webs: which statement is NOT true? (Animals often compete for food, water and space. / Predator and prey populations often rise and fall in cycles. / Plants compete for light, water and minerals. / Removing a predator always helps every other species.) → 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 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 8000 kJ. The next level gets 960 kJ. What is the percentage efficiency of the energy transfer? → 12 %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 8 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. Why do food chains rarely have more than four or five levels? (Plants stop growing / There are not enough names for them / There is too little energy left to support more levels / Top predators do not need energy) → There is too little energy left to support more levelsPrompt: Think about how much is left after several 10% steps.
2. A level of a food chain contains 10000 kJ. The next level gets 500 kJ. What is the percentage efficiency of the energy transfer? → 5 %Prompt: efficiency = energy passed on ÷ energy available × 100

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