Variation and Selection

Overview

In lesson 4 of 6 in Variation, Inheritance and Selection, students evaluate a contemporary example of selection: antibiotic resistance in bacteria. They connect inherited genetic variation with differential survival and reproduction, while assessing whether communicated information is supported by reliable scientific evidence.

Learning intentions

Students will:

• explain how genetic variation can arise and be inherited in a population
• explain how selection changes the frequency of characteristics over time
• distinguish scientific evidence from unsupported claims
• evaluate the reliability and purpose of sources about antibiotic resistance
• communicate an evidence-based evaluation using scientific language

Success criteria

• I can describe a source of genetic variation and connect it to an inherited characteristic.
• I can explain why some bacteria survive antibiotic treatment and reproduce.
• I can identify evidence, claims, source, purpose and scientific conventions in communicated information.
• I can use reliable evidence to evaluate the relationship between genetic variation and selection.

Curriculum links

• Genetic variation in relation to an identified characteristic: explaining and evaluating how variation occurs, is inherited, and is tracked in a population.
• Science-related claims in communicated information: identifying source, purpose, claims, evidence and scientific language, then evaluating how effectively evidence supports a claim.
• New Zealand Curriculum Nature of Science: understanding that science uses evidence, is tentative, and rigorously reviews claims.
• Thinking and participating-and-contributing competencies: critically evaluating information, discussing ideas respectfully, and contributing to a shared evidence-based conclusion.

Lesson structure (60 minutes)

1. 0–7 min · Hook and retrieval. Teacher opens with the antibiotic resistance hook slide and asks, “If antibiotics kill bacteria, why can infections become harder to treat?” Students complete a quick individual retrieval: define phenotype, genetic variation and selection, then compare answers with a partner.

2. 7–17 min · Direct teaching. Using the variation and selection explanation slides, teacher models the sequence: mutation creates variation; a bacterium with a resistance allele survives treatment; it reproduces; the resistance allele becomes more common. Students annotate the sequence on the variation and evidence worksheet and identify the characteristic, source of variation and nature of the variation.

3. 17–30 min · Evidence or claim? Teacher displays three short statements in the evidence-versus-claim slides and models the difference between a measurable result and a conclusion or claim. In pairs, students classify statements on the worksheet as evidence, claim, opinion or explanation, and justify one decision using scientific vocabulary.

4. 30–45 min · Source evaluation. Teacher introduces two contrasting, fictionalised source extracts in the source evaluation slides: a public-health research summary reporting resistance data and an antibiotic product advertisement making a broad promise. Students use the worksheet to record each source’s creator, intended purpose, claim, evidence, scientific language or conventions, and limitations. They rank which source is more reliable and explain why.

5. 45–55 min · Evaluate and communicate. Teacher sets the prompt: “Evaluate how genetic variation and selection contribute to antibiotic resistance, using evidence from the more reliable source.” Students plan and write a paragraph using the extended-response planning frame. Require a clear claim, two linked pieces of evidence, and a judgement about reliability or limitations. Partners check whether the explanation shows cause and effect rather than simply describing resistance.

6. 55–60 min · Plenary and exit ticket. Teacher returns to the hook question using the conclusion and exit-ticket slide. Students complete the worksheet exit ticket: “Explain why antibiotic resistance can increase in a population after antibiotic use. Name one feature that makes evidence reliable.” Invite two students to share responses and clarify one common misconception.

Resources

• the variation and selection slide deck
• the variation and evidence worksheet
• the extended-response planning frame
• Projector or interactive display
• Whiteboard and markers
• Pens or highlighters
• A timer
• Two fictionalised source extracts included in the worksheet

Assessment

• During retrieval and direct teaching, check whether students can distinguish a source of variation from the process of selection and use questioning to identify misconceptions.
• Review pair classifications and source-evaluation notes, looking for evidence-based justification rather than statements such as “it looks professional”.
• Collect the worksheet exit ticket and paragraph plan. Students working at a higher level should evaluate limitations and reach a supported judgement; students meeting the core intention should accurately link variation, inheritance, survival and reproduction.

Differentiation

• Provide a word bank on the worksheet: variation, mutation, allele, inherited, characteristic, selection, population, evidence, claim, reliable and limitation.
• Offer sentence starters: “The source of variation is…”, “Bacteria with this characteristic are more likely to…”, and “This source is more reliable because…”.
• Chunk the source extracts, read key sections aloud, and allow students to highlight evidence in one colour and claims in another. This supports EAL learners and students who need reading or processing assistance.
• Extend confident students by asking them to explain why antibiotic use does not create resistance because bacteria “need” it, and to evaluate what additional evidence would strengthen the source’s claim.