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Science lesson plan · 9th grade (Year 10 in England) · 30 minutes

Natural selection and resistance

Cells, genetics and evolution

CCSS NGSS.MS-LS4-4CCSS NGSS.HS-LS4-2CCSS NGSS.HS-LS4-4England: KS4 Combined Science: Evolution, inheritance and variation

Objective and success criteria

Students will: Natural selection and resistance.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Evolution and fossil evidence; DNA, genes and chromosomes

Leads to: Evidence for evolution and how new species form; Allele frequencies with the Hardy–Weinberg equations

Materials: Microscope images or slides, Cell diagrams, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • 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. Where is DNA found in an animal cell? (in the cell wall / mainly in the nucleus / in the chloroplasts / outside the cell) → mainly in the nucleusPrompt: It is the control centre of the cell.
  3. Evolution: which statement is true? (Individual animals evolve during their own lifetime. / Dinosaurs and early humans lived at the same time. / Fossils are evidence for evolution. / Humans evolved from modern chimpanzees.) → Fossils are evidence for evolution.Prompt: Evolution is about populations over many generations.

Hook · 3 min

  • 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.

I do: model it · 7 min

  • 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.

We do: guided practice · 6 min

  • 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 / animals choosing their own mates in the wild / feeding animals more food / 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 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.

You do: independent practice · 7 min

  • 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.

Exit ticket · 3 min

  • 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? (To make the antibiotic taste better / 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 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 1% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 10Prompt: Only the resistant ones survive.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Evolution and fossil evidence.
  • Use concrete materials: microscope images or slides.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Move on to: Evidence for evolution and how new species form; Allele frequencies with the Hardy–Weinberg equations.
  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

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

Free lesson plan from eurekami.com/lesson-plan-builder

eurekami

Natural selection and resistance

Name

Date

Score/ 6

  1. Question 1

    Before the Industrial Revolution most peppered moths were pale. Soot darkened tree bark, and dark moths became common. Why?

    • A. Soot changed the moths' genes directly
    • B. Dark moths were better camouflaged, so fewer were eaten by birds
    • C. Birds prefer to eat dark moths
    • D. Pale moths painted themselves dark

  2. Question 2

    A population of 500 bacteria contains 5% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive?

    Answer

  3. Question 3

    A population of 1000 bacteria contains 10% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive?

    Answer

  4. Question 4

    A population of 200 bacteria contains 2% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive?

    Answer

  5. Question 5

    Why should patients finish a course of antibiotics?

    • A. To make their immune system weaker
    • B. To kill all the bacteria, so resistant ones are less likely to survive and spread
    • C. Because antibiotics kill viruses
    • D. To make the antibiotic taste better

  6. Question 6

    A population of 100 bacteria contains 10% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive?

    Answer

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Answer key: Natural selection and resistance

  1. 1. B. Dark moths were better camouflaged, so fewer were eaten by birds

  2. 2. 25

  3. 3. 100

  4. 4. 4

  5. 5. B. To kill all the bacteria, so resistant ones are less likely to survive and spread

  6. 6. 10