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Science lesson plan · 8th grade (Year 9 in England) · 45 minutes

Use twins and clones to separate genes from environment

Cells, genetics and evolution

CCSS NGSS.MS-LS1-5CCSS NGSS.MS-LS3-2CCSS NGSS.SEP 7England: KS3 Biology: Inheritance, chromosomes, DNA and genesEngland: GCSE Combined Science: Inheritance, variation and evolution

Objective and success criteria

Students will: Use twins and clones to separate genes from environment.

  • 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: Genes, alleles, genotypes and phenotypes; Continuous and discontinuous variation

Leads to: the next skill in this area.

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 (Genes, alleles, genotypes and phenotypes; Continuous and discontinuous variation). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Which word means: the alleles an organism has, written like Bb? (heterozygous / homozygous / dominant / genotype) → genotypePrompt: “Geno-” is about the genes you carry; “pheno-” is about what you see.
  2. Is this continuous or discontinuous variation: ABO blood group? (continuous / discontinuous) → discontinuousPrompt: Can it have any value, or only a few set categories?
  3. An organism has the genotype Tt. How is this genotype described? (homozygous dominant / heterozygous / homozygous recessive) → heterozygousPrompt: Capital letters stand for dominant alleles.

Hook · 5 min

  • Show a microscope image of cells and ask what students think they are looking at.
  • Share the objective: Use twins and clones to separate genes from environment. 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: Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 49 cm, shade 32 cm. What can you conclude?
  • Step 1: Same genes, different conditions: the 17 cm difference is environmental.
  • Step 2: So the answer is: The difference in height was caused by the environment (light).
  • Answer: The difference in height was caused by the environment (light).
  • 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. Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 48 cm, shade 28 cm. What can you conclude? (The plants in the shade had different genes. / The difference in height was caused by the environment (light). / The results show light has no effect. / Height is controlled only by genes.) → The difference in height was caused by the environment (light).Prompt: Clones have identical genes.
  2. Hydrangea flowers of the same variety are blue in acidic soil and pink in alkaline soil. This is an example of… (environmental variation / natural selection / genetic variation / a mutation) → environmental variationPrompt: The plants have the same genes.

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. Genes and environment: which statement is NOT true? (Clones have identical genes. / Height depends on both genes and environment. / A suntan is caused by the environment. / Blood group is changed by diet.) → Blood group is changed by diet.Prompt: Can a characteristic caused by the environment be inherited?
  2. Why are identical twins so useful in studying variation? (They have the same genes, so differences must be environmental / They have no genes / They always live in the same house / They never vary at all) → They have the same genes, so differences must be environmentalPrompt: Which variable is controlled?

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: Genes, alleles, genotypes and phenotypes.
  • 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

  • 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-8.

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

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Use twins and clones to separate genes from environment

Name

Date

Score/ 8

  1. Question 1

    Hydrangea flowers of the same variety are blue in acidic soil and pink in alkaline soil. This is an example of…

    • A. genetic variation
    • B. a mutation
    • C. natural selection
    • D. environmental variation

  2. Question 2

    Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 38 cm, shade 28 cm. What can you conclude?

    • A. The results show light has no effect.
    • B. The difference in height was caused by the environment (light).
    • C. The plants in the shade had different genes.
    • D. Height is controlled only by genes.

  3. Question 3

    Genes and environment: which statement is NOT true?

    • A. A suntan is caused by the environment.
    • B. Identical twins always have identical body mass.
    • C. Height depends on both genes and environment.
    • D. Clones have identical genes.

  4. Question 4

    Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 49 cm, shade 32 cm. What can you conclude?

    • A. The difference in height was caused by the environment (light).
    • B. The results show light has no effect.
    • C. Height is controlled only by genes.
    • D. The plants in the shade had different genes.

  5. Question 5

    Why are identical twins so useful in studying variation?

    • A. They have no genes
    • B. They never vary at all
    • C. They always live in the same house
    • D. They have the same genes, so differences must be environmental

  6. Question 6

    Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 52 cm, shade 35 cm. What can you conclude?

    • A. The difference in height was caused by the environment (light).
    • B. Height is controlled only by genes.
    • C. The results show light has no effect.
    • D. The plants in the shade had different genes.

  7. Question 7

    Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 48 cm, shade 32 cm. What can you conclude?

    • A. The difference in height was caused by the environment (light).
    • B. The results show light has no effect.
    • C. Height is controlled only by genes.
    • D. The plants in the shade had different genes.

  8. Question 8

    Two rabbits from the same litter are fed different diets and grow to different sizes. Why can we not be sure the difference is only due to diet?

    • A. Rabbits do not have genes
    • B. Brothers and sisters do not have identical genes
    • C. Diet never affects size
    • D. The rabbits are clones

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Answer key: Use twins and clones to separate genes from environment

  1. 1. D. environmental variation

  2. 2. B. The difference in height was caused by the environment (light).

  3. 3. B. Identical twins always have identical body mass.

  4. 4. A. The difference in height was caused by the environment (light).

  5. 5. D. They have the same genes, so differences must be environmental

  6. 6. A. The difference in height was caused by the environment (light).

  7. 7. A. The difference in height was caused by the environment (light).

  8. 8. B. Brothers and sisters do not have identical genes