• Quick retrieval from earlier learning (Evolution and fossil evidence; DNA, genes and chromosomes). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Finches on different islands have different beak shapes. The best explanation is… (Beak shape is random and has no effect. / Beaks suited to each island's food helped birds survive and breed. / The birds chose their beak shape. / Each bird stretched its beak to reach food.) → Beaks suited to each island's food helped birds survive and breed.Prompt: Which birds would have had more chicks?
2. What shape is a DNA molecule? (a single straight line / a cube / a ring of six atoms / a double helix) → a double helixPrompt: It looks like a twisted ladder.
3. Evolution: which statement is true? (Humans evolved from modern chimpanzees. / Dinosaurs and early humans lived at the same time. / Variation between individuals is needed for natural selection. / Individual animals evolve during their own lifetime.) → Variation between individuals is needed for natural selection.Prompt: Evolution is about populations over many generations.

• Show a microscope image of cells and ask what students think they are looking at.
• Share the objective: Natural selection and resistance. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Before the Industrial Revolution most peppered moths were pale. Soot darkened tree bark, and dark moths became common. Why?
• Step 1: Dark moths survived to breed more, so the dark allele became more common.
• Step 2: So the answer is: Dark moths were better camouflaged, so fewer were eaten by birds
• Answer: Dark moths were better camouflaged, so fewer were eaten by birds
• 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. Why should patients finish a course of antibiotics? (Because antibiotics kill viruses / To make their immune system weaker / To kill all the bacteria, so resistant ones are less likely to survive and spread / To make the antibiotic taste better) → To kill all the bacteria, so resistant ones are less likely to survive and spreadPrompt: Stopping early can leave the toughest bacteria alive.
2. A population of 1000 bacteria contains 1% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 10Prompt: Only the resistant ones survive.

• 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. What is selective breeding? (humans choosing parents with useful characteristics to breed / animals choosing their own mates in the wild / cloning one plant / feeding animals more food) → humans choosing parents with useful characteristics to breedPrompt: Farmers have done this for thousands of years.
2. A population of 500 bacteria contains 10% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 50Prompt: Only the resistant ones survive.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-9.