Explaining an Identified Characteristic

Overview

This is lesson 5 of 6 in the unit Variation, Inheritance and Selection. Students synthesise their prior learning about alleles, mutation, sexual reproduction, inheritance, environmental effects and selection to construct an evidence-based explanation of one identified characteristic.

Learning intentions

• WALT describe how genetic variation relates to an identified characteristic.
• WALT explain how alleles are inherited and how environmental factors may influence phenotype.
• WALT use evidence, scientific language and symbols to construct a coherent explanation.
• WALT evaluate the strength and limitations of a gene-tracking approach.

Success criteria

• I can identify the characteristic and distinguish genotype from phenotype.
• I can link alleles, inheritance and at least one source of genetic variation to the characteristic.
• I can explain how the environment and selection may influence the characteristic where relevant.
• I can use evidence and appropriate scientific terms, symbols and written conventions.

Curriculum links

• Demonstrate understanding of genetic variation in relation to an identified characteristic: source, nature and gene-tracking methodology.
• Demonstrate understanding of the use of a range of scientific investigative approaches in a context: using patterns and evidence to answer a question.
• Demonstrate understanding of science-related claims in communicated information: interpreting scientific language, evidence and conventions.
• New Zealand Curriculum Level 6 Science: communicating in science, developing explanations from evidence, and participating and contributing.

Lesson structure (60 minutes)

1. 0–5 min · Retrieval hook. Teacher displays a photograph of people with different inherited characteristics and asks, “Does a phenotype always reveal an individual’s genotype?” using the opening image and retrieval question. Students complete a silent think, then share one idea with a partner.

2. 5–15 min · Model the explanation. Teacher revisits the distinction between gene, allele, genotype, phenotype, inherited variation and environmental influence, then models a short explanation using human lactose tolerance or another familiar characteristic in the key concept and model explanation slides. Students annotate the model, identifying the characteristic, alleles, source of variation, inheritance pattern, evidence and any environmental influence.

3. 15–23 min · Evidence and gene tracking. Teacher presents a simplified data set showing the presence or absence of a genetic marker alongside the characteristic, and discusses what gene tracking can and cannot show. Students answer the prompts: “What pattern is shown?”, “What conclusion is justified?”, and “What further evidence would be useful?” They record their answers on the genetic variation explanation worksheet.

4. 23–43 min · Construct an evidence-based response. Teacher assigns or allows students to select one identified characteristic, such as sickle-cell resistance to malaria, albinism in a population, human blood groups, or antibiotic resistance in bacteria. Students use the extended-response planning frame and the genetic variation explanation worksheet to plan and write a structured response. The response must include:

• the characteristic and differences in phenotype;
• the relevant gene or alleles and how they are inherited;
• a source of variation, such as mutation or sexual reproduction;
• the nature or consequence of the variation;
• environmental influence and selection where relevant;
• how a gene-tracking method could identify relationships or patterns;
• evidence supporting the explanation.

5. 43–53 min · Peer review and improvement. Teacher displays a peer-review checklist through the response checklist and discussion prompts. Students exchange responses with a partner and highlight one clear link, underline scientific evidence, and write one question or improvement. Writers revise at least one section, checking that claims are not stronger than the evidence allows.

6. 53–60 min · Plenary and exit check. Teacher asks students to complete the final prompt on the explanation and exit-ticket section: “Explain how one source of genetic variation can lead to differences in an identified characteristic, and state one limitation of using a genetic marker to track relationships.” Invite two students to share contrasting answers, then collect responses to identify needs for the final lesson.

Resources

• the genetic variation explanation slide deck
• the genetic variation explanation worksheet
• the extended-response planning frame
• Projector or interactive display
• Simplified genetic-marker data set
• Student exercise books or devices
• Highlighters or coloured pens
• Timer

Assessment

• During retrieval and discussion, listen for accurate use of gene, allele, genotype, phenotype, mutation, inheritance and selection.
• Confer with students during planning, checking that each explanation links evidence to a claim rather than listing terms.
• Use the exit response to assess whether students can explain a source and consequence of variation and recognise a limitation of gene tracking.

Differentiation

• Provide a completed example, a word bank and sentence starters such as “The characteristic varies because…”, “The allele is inherited when…”, and “The evidence suggests…”.
• Offer students who need support a partially completed planning frame and a reduced data set with key patterns highlighted.
• Encourage confident students to compare two possible explanations, distinguish correlation from causation, and evaluate whether the marker is a reliable indicator of the characteristic.
• Allow speech-to-text, oral rehearsal before writing, enlarged resources and paired reading. Check that examples do not require students to disclose personal genetic or health information.