Variation and Survival

Overview

In this third lesson of the six-lesson unit Variation, Inheritance and Selection, students connect inherited genetic variation with environmental conditions and differences in survival. Using a case study of peppered moths, they interpret evidence, discuss competing explanations, and explain why a variation can be advantageous in one environment but disadvantageous in another.

Learning intentions

• WALT identify genetic variation in an identified characteristic.
• WALT interpret evidence about survival in different environments.
• WALT explain how environmental conditions can make a variation advantageous or disadvantageous.
• WALT use evidence to support collaborative scientific discussion.

Success criteria

• I can identify the characteristic and genetic variation shown in a case study.
• I can describe patterns in evidence about survival.
• I can explain how the environment affects which variation is advantageous.
• I can use specific evidence to support, question, or revise an explanation.

Curriculum links

• Genetic variation in relation to an identified characteristic: sources, nature, and gene tracking purposes.
• Scientific investigative approaches: interpreting patterns and using evidence to answer a question.
• Nature of Science: investigating the world, communicating explanations, and evaluating scientific claims.
• Key competencies: thinking; participating and contributing; relating to others; using language, symbols, and texts.

Lesson structure (60 minutes)

1. 0–5 min · Hook and retrieval. Teacher displays the opening moth image and prediction question and asks, “Why might two organisms with different appearances have different chances of surviving?” Students write an individual prediction, then share one idea with a partner. Briefly revisit that genetic variation means inherited differences in DNA or genetic markers, rather than changes caused by training, injury, or choice.

2. 5–15 min · Direct teaching and model. Teacher uses the case-study background and key vocabulary slides to introduce the peppered moth characteristic: wing colour. Explain that mutation creates alternative alleles and sexual reproduction reshuffles existing alleles; environmental conditions can affect camouflage and predation. Model the difference between describing evidence (“more dark moths survived”) and explaining it (“dark moths were less visible on dark tree trunks, reducing predation”). Students complete the “characteristic–variation–environment–survival” boxes on the variation and survival evidence worksheet.

3. 15–30 min · Evidence interpretation. Teacher distributes the worksheet and guides students through a simplified data table comparing light and dark moth survival before and after industrial pollution. Students work in pairs to calculate or compare survival percentages, identify the main pattern, and annotate the data with two evidence statements. Ask pairs to check: What is being compared? What stays the same? What evidence supports camouflage as an explanation? Circulate and question students without confirming answers too quickly.

4. 30–42 min · Collaborative evidence discussion. Teacher displays the discussion roles and evidence prompts and assigns groups of four roles: evidence finder, environmental link, challenger, and reporter. Groups discuss the claim: “A dark wing colour is always an advantage.” Students must decide whether they agree, disagree, or need a more precise claim, using at least two pieces of evidence from the case study. The challenger asks, “Would the same variation be advantageous in a different environment?” Groups record their revised claim and reasoning on the worksheet.

5. 42–53 min · Independent explanation. Teacher models a paragraph structure on the explanation scaffold: identify the variation, describe the environmental condition, state the survival pattern, and link the pattern to a biological reason. Students independently answer: “Explain how wing-colour variation may affect survival in two different environments.” Require a clear distinction between the source of variation and the environmental factor that affects survival. Students underline their evidence and circle their explanation.

6. 53–60 min · Plenary and exit check. Teacher uses the final challenge and recap to revisit the learning intention. Students complete the worksheet exit ticket: “Explain why a genetic variation can be beneficial in one environment but not another. Include one piece of evidence.” Invite two students to share different-quality answers and ask the class which answer best connects variation, environment, and survival.

Resources

• the Variation and Survival teaching deck
• the variation and survival evidence worksheet
• Projector or interactive display
• Whiteboard and markers
• Calculators, optional
• Highlighters or coloured pencils
• Timer

Assessment

• Check retrieval responses and questioning during the opening to identify misconceptions about inherited versus acquired characteristics.
• Formatively assess pair data annotations and group claims for accurate interpretation of patterns and use of evidence.
• Collect the exit ticket and independent explanation, looking for a linked explanation of genetic variation, environmental conditions, and survival differences.

Differentiation

• Provide a word bank on the worksheet: genetic variation, characteristic, allele, mutation, camouflage, environment, predation, survival, advantageous, and disadvantageous.
• Support students with a partially completed model paragraph and sentence starters such as “The characteristic is…”, “The evidence shows…”, and “This may increase survival because…”.
• Pair students strategically and allow oral rehearsal before writing; provide enlarged data and read the case-study text aloud for students with literacy or visual-processing needs.
• Extend confident students by asking them to evaluate whether the evidence demonstrates genetic inheritance directly, or whether an additional gene-tracking method would be needed to support that conclusion.