• 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? (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 200 bacteria contains 2% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 4Prompt: Only the resistant ones survive.
3. Before the Industrial Revolution most peppered moths were pale. Soot darkened tree bark, and dark moths became common. Why? (Soot changed the moths' genes directly / Dark moths were better camouflaged, so fewer were eaten by birds / Birds prefer to eat dark moths / Pale moths painted themselves dark) → Dark moths were better camouflaged, so fewer were eaten by birdsPrompt: Which moths could birds see more easily on dark bark?

• 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 %, orangutan 3.1 %. Which primate shares the most recent common ancestor with humans? (orangutan / rhesus macaque / chimpanzee) → 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? (We can watch natural selection change a population in real time / 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 timePrompt: Bacteria reproduce very quickly.

• 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. Approximate % difference between human DNA and other primates: gorilla 1.6 %, orangutan 3.1 %, rhesus macaque 7 %. 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. Bacteria that resist the antibiotic used against them appear within years. Why is this evidence for evolution? (Antibiotics create the resistance gene on purpose / Bacteria choose to become resistant / It shows bacteria never mutate / 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.

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