• 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. What is the original source of new variation in a population? (learning new skills / injuries / mutations in DNA / exercise) → mutations in DNAPrompt: It is a change in the genetic code.
2. A population of 100 bacteria contains 10% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 10Prompt: Only the resistant ones survive.
3. What is selective breeding? (cloning one plant / humans choosing parents with useful characteristics to breed / feeding animals more food / animals choosing their own mates in the wild) → humans choosing parents with useful characteristics to breedPrompt: Farmers have done this for thousands of years.

• 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: rhesus macaque 7 %, chimpanzee 1.2 %, gorilla 1.6 %. Which primate shares the most recent common ancestor with humans? (rhesus macaque / chimpanzee / gorilla) → chimpanzeePrompt: 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 / It is a coincidence / Bats evolved from whales / 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 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. Approximate % difference between human DNA and other primates: orangutan 3.1 %, gorilla 1.6 %, chimpanzee 1.2 %. Which primate shares the most recent common ancestor with humans? (chimpanzee / gorilla / orangutan) → chimpanzeePrompt: Fewer DNA differences means less time since the two lines split.
2. Bacteria that resist the antibiotic used against them appear within years. Why is this evidence for evolution? (It shows bacteria never mutate / We can watch natural selection change a population in real time / Bacteria choose to become resistant / Antibiotics create the resistance gene on purpose) → We can watch natural selection change a population in real timePrompt: Bacteria reproduce very quickly.

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