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Science lesson plan · 9th grade (Year 10 in England) · 60 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 · 6 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… (finding important fossils, such as ichthyosaurs / discovering electricity / landing on the Moon / inventing the telescope) → finding important fossils, such as ichthyosaursPrompt: She searched the cliffs of the Jurassic Coast in England.
  2. How many chromosomes are in a normal human body cell? (92 / 23 / 12 / 46 (23 pairs)) → 46 (23 pairs)Prompt: They come in pairs, one of each pair from each parent.
  3. Evolution: which statement is true? (Fossils are evidence for evolution. / Humans evolved from modern chimpanzees. / Dinosaurs and early humans lived at the same time. / Individual animals evolve during their own lifetime.) → Fossils are evidence for evolution.Prompt: Evolution is about populations over many generations.

Hook · 6 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 · 12 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 · 12 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 the original source of new variation in a population? (exercise / learning new skills / mutations in DNA / injuries) → mutations in DNAPrompt: It is a change in the genetic code.
  2. A population of 1000 bacteria contains 5% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 50Prompt: Only the resistant ones survive.

You do: independent practice · 17 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 · 7 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. A population of 1000 bacteria contains 10% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive? → 100Prompt: Only the resistant ones survive.
  2. What is selective breeding? (animals choosing their own mates in the wild / cloning one plant / 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.

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

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Natural selection and resistance

Name

Date

Score/ 8

  1. Question 1

    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. Pale moths painted themselves dark
    • C. Soot changed the moths' genes directly
    • D. Birds prefer to eat dark moths

  2. Question 2

    A population of 500 bacteria contains 1% that are resistant to an antibiotic. The antibiotic kills all the others. How many bacteria survive?

    Answer

  3. Question 3

    What is selective breeding?

    • A. animals choosing their own mates in the wild
    • B. cloning one plant
    • C. feeding animals more food
    • D. humans choosing parents with useful characteristics to breed

  4. Question 4

    A population of 1000 bacteria contains 5% 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. Because antibiotics kill viruses
    • B. To kill all the bacteria, so resistant ones are less likely to survive and spread
    • C. To make the antibiotic taste better
    • D. To make their immune system weaker

  6. Question 6

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

    Answer

  7. Question 7

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

    Answer

  8. Question 8

    A population of 500 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. A. Dark moths were better camouflaged, so fewer were eaten by birds

  2. 2. 5

  3. 3. D. humans choosing parents with useful characteristics to breed

  4. 4. 50

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

  6. 6. 25

  7. 7. 100

  8. 8. 50