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Science lesson plan · 9th grade (Year 10 in England) · 45 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 · 5 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. Mary Anning was famous for… (landing on the Moon / finding important fossils, such as ichthyosaurs / inventing the telescope / discovering electricity) → finding important fossils, such as ichthyosaursPrompt: She searched the cliffs of the Jurassic Coast in England.
  2. What shape is a DNA molecule? (a ring of six atoms / a single straight line / a cube / a double helix) → a double helixPrompt: It looks like a twisted ladder.
  3. Evolution: which statement is true? (Dinosaurs and early humans lived at the same time. / Variation between individuals is needed for natural selection. / Individual animals evolve during their own lifetime. / Humans evolved from modern chimpanzees.) → Variation between individuals is needed for natural selection.Prompt: Evolution is about populations over many generations.

Hook · 5 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 · 10 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 · 10 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? (feeding animals more food / animals choosing their own mates in the wild / cloning one plant / 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 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.

You do: independent practice · 10 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 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. 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.
  2. A population of 500 bacteria contains 5% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 25Prompt: 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/ 8

  1. Question 1

    What is the original source of new variation in a population?

    • A. injuries
    • B. mutations in DNA
    • C. learning new skills
    • D. exercise

  2. Question 2

    A population of 200 bacteria contains 1% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive?

    Answer

  3. Question 3

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

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

  4. Question 4

    A population of 200 bacteria contains 10% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive?

    Answer

  5. Question 5

    A population of 1000 bacteria contains 1% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive?

    Answer

  6. Question 6

    A population of 100 bacteria contains 1% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive?

    Answer

  7. Question 7

    A population of 200 bacteria contains 5% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive?

    Answer

  8. Question 8

    A population of 200 bacteria contains 2% 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. mutations in DNA

  2. 2. 2

  3. 3. A. Dark moths were better camouflaged, so fewer were eaten by birds

  4. 4. 20

  5. 5. 10

  6. 6. 1

  7. 7. 10

  8. 8. 4