• Quick retrieval from earlier learning (Natural selection and resistance). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Why should patients finish a course of antibiotics? (To kill all the bacteria, so resistant ones are less likely to survive and spread / Because antibiotics kill viruses / 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 100 bacteria contains 5% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 5Prompt: Only the resistant ones survive.
3. What is the original source of new variation in a population? (injuries / mutations in DNA / exercise / learning new skills) → mutations in DNAPrompt: It is a change in the genetic code.

• Show a microscope image of cells and ask what students think they are looking at.
• Share the objective: Evidence for evolution and how new species form. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Approximate % difference between human DNA and other primates: chimpanzee 1.2 %, orangutan 3.1 %, rhesus macaque 7 %. Which primate shares the most recent common ancestor with humans?
• Step 1: The smallest difference is 1.2 %.
• Step 2: So the answer is: chimpanzee
• Answer: chimpanzee
• 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. Approximate % difference between human DNA and other primates: gorilla 1.6 %, rhesus macaque 7 %, orangutan 3.1 %. Which primate shares the most recent common ancestor with humans? (gorilla / rhesus macaque / orangutan) → gorillaPrompt: Fewer DNA differences means less time since the two lines split.
2. The arm of a human, the wing of a bat and the flipper of a whale have the same arrangement of bones. What does this suggest? (They evolved from a common ancestor / Bats evolved from whales / It is a coincidence / They were designed for the same job) → They evolved from a common ancestorPrompt: The limbs do different jobs but share a pattern.

• 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. Bacteria that resist the antibiotic used against them appear within years. Why is this evidence for evolution? (It shows bacteria never mutate / Bacteria choose to become resistant / Antibiotics create the resistance gene on purpose / We can watch natural selection change a population in real time) → We can watch natural selection change a population in real timePrompt: Bacteria reproduce very quickly.
2. Approximate % difference between human DNA and other primates: rhesus macaque 7 %, orangutan 3.1 %, gorilla 1.6 %. Which primate shares the most recent common ancestor with humans? (gorilla / orangutan / rhesus macaque) → gorillaPrompt: Fewer DNA differences means less time since the two lines split.

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