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Interactive Cladogram Builder

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About This MicroSim

This interactive cladogram builder teaches students how phylogenetic trees are constructed from shared derived characters (synapomorphies). A character matrix on the left shows which traits each species possesses. Students drag species labels from a pool and drop them onto the correct tip positions on the cladogram tree on the right. Trait markers at branch points show where each character evolved. Two datasets are available: Vertebrates (6 species, 6 traits) and Arthropods (5 species, 5 traits).

How to Use

  1. Read the character matrix on the left — each row is a species, each column is a trait, and checkmarks indicate which traits that species has.
  2. Drag species labels from the pool at the bottom and drop them onto the numbered tip slots on the cladogram tree.
  3. Rearrange species by dragging them from one slot to another — they will swap positions.
  4. Click "Check" to verify your placement — correct positions get a green checkmark, incorrect ones get a red X.
  5. Toggle "Hints" to see which traits mark each branch point (orange diamonds on the tree).
  6. Switch datasets using the Vertebrates/Arthropods buttons to practice with different organisms.
  7. Click "Reset" to return all species to the pool and try again.

Lesson Plan

Grade Level

9-12 (college placement Biology)

Duration

10-15 minutes

Prerequisites

  • Understanding of evolutionary relationships and common ancestry
  • Knowledge of homologous vs. analogous structures
  • Familiarity with the concept of shared derived characters (synapomorphies)

Activities

  1. Exploration (5 min): Select the Vertebrates dataset. Examine the character matrix and identify which species share the most traits. Try placing species on the tree and check your answer. Which species is most basal (fewest derived traits)? Which two species are most closely related?
  2. Guided Practice (5 min): Turn on Hints to see trait markers at branch points. Notice how each branch point represents the evolution of a new trait shared by all species above that node. Reset and try the Arthropods dataset — apply the same logic to a different group of organisms.
  3. Assessment (5 min): Without hints, correctly place all species in both datasets. Then answer: Why is the lamprey placed at the base of the vertebrate cladogram? What trait unites the pigeon and mouse but excludes the lizard? How does the number of shared traits relate to evolutionary distance?

Assessment

  • Can students correctly place all species on the cladogram using the character matrix?
  • Can students explain why shared derived characters indicate closer evolutionary relationships?
  • Can students identify the most recent common ancestor of any two species on the tree?
  • Can students predict which traits a newly discovered species might have based on its position on the tree?

References

  1. Cladistics - Wikipedia
  2. Phylogenetic tree - Wikipedia
  3. Synapomorphy - Wikipedia