• 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 all the small fish died, what would probably happen to the tadpoles at first? (They would decrease / They would stay exactly the same / They would increase / They would turn into fish) → They would increasePrompt: What eats tadpoles?
2. Rabbits and sheep both eat grass in the same field. This is an example of… (predation / decomposition / photosynthesis / competition) → competitionPrompt: They both want the same limited resource.
3. Food webs: which statement is NOT true? (A food web contains only one food chain. / Predator and prey populations often rise and fall in cycles. / Plants compete for light, water and minerals. / Removing one species can affect many others in a food web.) → 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 hedgehogs counted in a survey in 2010 and 180 in 2024. What was the percentage decrease? → 10 %Prompt: Find the decrease first.
2. Why is high biodiversity good for an ecosystem? (It removes all predators / It stops the water cycle / It means fewer species compete / It makes the ecosystem more stable because species depend on many others) → 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. Biodiversity: which statement is NOT true? (Fertiliser running into lakes can cause algae to grow and oxygen to fall. / Breeding programmes can help protect endangered species. / Biodiversity means the number of individuals of one species. / Global warming is changing where some species can live.) → Biodiversity means the number of individuals of one species.Prompt: What does biodiversity actually measure?
2. Rewilding projects reintroduce species such as beavers. What can beavers do for an ecosystem? (Their dams create wetlands that support many other species and reduce flooding downstream / They have no effect / They remove all fish / They make rivers flow faster) → Their dams create wetlands that support many other species and reduce flooding downstreamPrompt: Beavers are called "ecosystem engineers".

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