• 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. Pond food web: algae are eaten by tadpoles and water fleas. Tadpoles and water fleas are eaten by small fish. Small fish are eaten by herons. If the small fish died, what would happen to the herons? (Nothing / They would increase / They would eat algae / They would decrease or move away) → They would decrease or move awayPrompt: What do herons eat in this web?
2. What does "interdependence" mean in an ecosystem? (Living things depend on each other, so a change to one affects others / Every animal lives alone / Plants do not need animals at all / Only predators matter) → Living things depend on each other, so a change to one affects othersPrompt: Think of bees and flowers.
3. Food webs: which statement is NOT true? (Plants compete for light, water and minerals. / Predator and prey populations often rise and fall in cycles. / Animals often compete for food, water and space. / A food web contains only one food chain.) → A food web contains only one food chain.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: Biodiversity under pressure and how we protect it. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: A survey found 200 breeding pairs of a bird species in 2010 and 180 in 2024. What was the percentage decrease?
• Step 1: 200 − 180 = 20
• Step 2: 20 ÷ 200 × 100 = 10
• Step 3: So the answer is: 10 %
• Answer: 10 %
• 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. A survey found 200 breeding pairs of a bird species in 2010 and 160 in 2024. What was the percentage decrease? → 20 %Prompt: Find the decrease first.
2. Why is high biodiversity good for an ecosystem? (It makes the ecosystem more stable because species depend on many others / It stops the water cycle / It means fewer species compete / It removes all predators) → It makes the ecosystem more stable because species depend on many othersPrompt: Think about what happens if one food source disappears.

• 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. A survey found 120 hectares of rainforest in 2010 and 84 in 2024. What was the percentage decrease? → 30 %Prompt: Find the decrease first.
2. Draining peat bogs to sell peat as garden compost harms the climate. Why? (It makes the ozone layer thicker / It creates acid rain / Peat absorbs too much oxygen / Decaying or burned peat releases stored carbon as carbon dioxide) → Decaying or burned peat releases stored carbon as carbon dioxidePrompt: Peat is partly decayed plant material.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-10.