Lesson Plan

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Lesson Plan
Grade: Date: 17/01/2026
Subject: Biology
Lesson Topic: discuss how DNA sequence data can show evolutionary relationships between species
Learning Objective/s:
  • Describe how DNA sequence similarity reflects evolutionary relationships.
  • Explain the process of constructing a phylogenetic tree from gene sequences.
  • Evaluate factors that can mislead molecular phylogenies.
  • Compare molecular evidence with morphological and fossil data.
  • Apply percentage identity and genetic‑distance calculations to infer relatedness.
Materials Needed:
  • Projector and screen
  • Computer with internet access
  • Printed sample DNA sequence dataset
  • Multiple‑sequence‑alignment tool (e.g., Clustal Omega)
  • Phylogenetic tree software or online neighbour‑joining tool (e.g., MEGA)
  • Worksheet for calculations
  • Whiteboard and markers
 Introduction:
Begin with a quick poll: which species do you think are most closely related – humans, mice, or frogs? Review prior knowledge that DNA mutations accumulate over time, acting like a molecular clock. Explain that by the end of the lesson students will be able to interpret percentage identity and construct a simple phylogenetic tree.
Lesson Structure:
  1. Do‑now (5') – Students answer the poll question on sticky notes.
  2. Mini‑lecture (10') – Review DNA as a molecular record and introduce similarity metrics (percentage identity, genetic distance).
  3. Guided practice (15') – Align the sample sequences using an online tool and calculate % identity.
  4. Group activity (15') – Convert % identity to genetic distance, build a distance matrix, and construct a neighbour‑joining tree on paper.
  5. Whole‑class discussion (10') – Interpret the tree and discuss potential pitfalls (horizontal gene transfer, rate heterogeneity, paralogy).
  6. Check for understanding (5') – Exit ticket: write one sentence explaining how % identity informs evolutionary relationship.
Conclusion:
Summarise that higher DNA similarity indicates recent common ancestry and that phylogenetic trees visualise these relationships. For the exit ticket, students write a brief explanation of one factor that could mislead a molecular tree. Homework: read the suggested chapter on phylogenetic methods and complete the worksheet on calculating genetic distance.