• 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. What do fossils tell us about living things? (Dinosaurs lived at the same time as the first humans. / Living things have changed over very long periods of time. / Living things have never changed. / Fossils are only made of plastic.) → Living things have changed over very long periods of time.Prompt: Older rock layers contain different fossils from newer ones.
2. What is a gene? (a disease / a type of cell / a whole chromosome / a section of DNA that codes for a protein) → a section of DNA that codes for a proteinPrompt: Genes are found along chromosomes.
3. Evolution: which statement is true? (Humans evolved from modern chimpanzees. / Dinosaurs and early humans lived at the same time. / Individual animals evolve during their own lifetime. / Fossils are evidence for evolution.) → Fossils are evidence for evolution.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? (To make the antibiotic taste better / To make their immune system weaker / To kill all the bacteria, so resistant ones are less likely to survive and spread / Because antibiotics kill viruses) → 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 10% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 100Prompt: 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 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 should patients finish a course of antibiotics? (Because antibiotics kill viruses / To kill all the bacteria, so resistant ones are less likely to survive and spread / To make their immune system weaker / 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 500 bacteria contains 2% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 10Prompt: Only the resistant ones survive.

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