Science lesson plan · 8th grade (Year 9 in England) · 60 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 · 6 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: having two different alleles, such as Bb? (allele / heterozygous / dominant / phenotype) → heterozygousPrompt: “Geno-” is about the genes you carry; “pheno-” is about what you see.
- Is this continuous or discontinuous variation: height? (continuous / discontinuous) → continuousPrompt: Can it have any value, or only a few set categories?
- The allele G (green pods) is dominant over g. An organism has genotype gg. What is its phenotype? (shows green pods / does not show green pods) → does not show green podsPrompt: One copy of a dominant allele is enough.
Hook · 6 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 · 12 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 · 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.
- 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 38 cm. What can you conclude? (Height is controlled only by genes. / The results show light has no effect. / The plants in the shade had different genes. / The difference in height was caused by the environment (light).) → The difference in height was caused by the environment (light).Prompt: Clones have identical genes.
- 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? (Diet never affects size / Brothers and sisters do not have identical genes / The rabbits are clones / Rabbits do not have genes) → Brothers and sisters do not have identical genesPrompt: Only identical twins and clones share all their genes.
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.
- Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 40 cm, shade 28 cm. What can you conclude? (Height is controlled only by genes. / The plants in the shade had different genes. / The results show light has no effect. / The difference in height was caused by the environment (light).) → The difference in height was caused by the environment (light).Prompt: Clones have identical genes.
- Hydrangea flowers of the same variety are blue in acidic soil and pink in alkaline soil. This is an example of… (natural selection / genetic variation / a mutation / environmental variation) → environmental variationPrompt: The plants have the same genes.
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