• 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. Who is famous for the theory of evolution by natural selection? (Isaac Newton / Marie Curie / Albert Einstein / Charles Darwin) → Charles DarwinPrompt: He studied finches and tortoises on the Galápagos Islands.
2. Rosalind Franklin's X-ray image helped scientists discover… (penicillin / the structure of DNA / the shape of the Earth / the first vaccine) → the structure of DNAPrompt: Watson and Crick used her data.
3. Evolution: which statement is true? (Individual animals evolve during their own lifetime. / Humans evolved from modern chimpanzees. / Dinosaurs and early humans lived at the same time. / Variation between individuals is needed for natural selection.) → 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. What is selective breeding? (cloning one plant / feeding animals more food / animals choosing their own mates in the wild / humans choosing parents with useful characteristics to breed) → humans choosing parents with useful characteristics to breedPrompt: Farmers have done this for thousands of years.
2. A population of 500 bacteria contains 5% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 25Prompt: 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. 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.
2. Before the Industrial Revolution most peppered moths were pale. Soot darkened tree bark, and dark moths became common. Why? (Dark moths were better camouflaged, so fewer were eaten by birds / Pale moths painted themselves dark / Birds prefer to eat dark moths / Soot changed the moths' genes directly) → Dark moths were better camouflaged, so fewer were eaten by birdsPrompt: Which moths could birds see more easily on dark bark?

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