Science lesson plan · 8th grade (Year 9 in England) · 30 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 · 4 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.
- Which word means: an allele that only shows its effect when two copies are present? (recessive / homozygous / dominant / genotype) → recessivePrompt: “Geno-” is about the genes you carry; “pheno-” is about what you see.
- Is this continuous or discontinuous variation: body mass? (continuous / discontinuous) → continuousPrompt: Can it have any value, or only a few set categories?
- An organism has the genotype rr. How is this genotype described? (homozygous dominant / heterozygous / homozygous recessive) → homozygous recessivePrompt: Capital letters stand for dominant alleles.
Hook · 3 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 · 7 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 · 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.
- Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 55 cm, shade 45 cm. What can you conclude? (The difference in height was caused by the environment (light). / The results show light has no effect. / The plants in the shade had different genes. / Height is controlled only by genes.) → The difference in height was caused by the environment (light).Prompt: Clones have identical genes.
- Identical twins raised apart often have very similar blood groups and eye colour but different body mass. What does this suggest? (Twins have different genes / All three are purely environmental / Body mass is purely genetic / Blood group is genetic; body mass is affected a lot by environment) → Blood group is genetic; body mass is affected a lot by environmentPrompt: Identical twins share all their genes.
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.
- Genes and environment: which statement is NOT true? (A suntan is caused by the environment. / Environmental variation is passed on to offspring. / Height depends on both genes and environment. / Differences between identical twins are caused by the environment.) → Environmental variation is passed on to offspring.Prompt: Can a characteristic caused by the environment be inherited?
- Why are identical twins so useful in studying variation? (They always live in the same house / They have the same genes, so differences must be environmental / They have no genes / 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