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AP® Biology · Unit 7 · Topic 7.9

Phylogeny: Topic Checklist (Biology 7.9)

Specific “I can…” statements for reading and building cladograms and phylogenetic trees, each linked to the guide section and practice question that shows whether you can really do it.

Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.

Understanding

  • I can explain why a phylogenetic tree or cladogram is a hypothesis that can be tested and revised, and give an example of a revision. (Guide: “A tree is a hypothesis about history” and “A real revision”; Practice Q7)
  • I can label the root, nodes, tips and a clade on a tree, and explain that a node is the most recent common ancestor of the lineages beyond it. (Guide: “Reading a tree”; Practice Q1)
  • I can explain the difference between a cladogram and a phylogenetic tree, and name the two ways time is calibrated. (Guide: Figure 1; Practice Q3)
  • I can explain the difference between ancestral, derived and shared derived characters, including traits that were lost. (Guide: “Building a tree from traits”; Practice Q4)
  • I can compare morphological, fossil, DNA and protein evidence, and explain why molecular data are usually more reliable. (Guide: “Evidence” table; Practice Q6)

Calculation and skills

  • I can build a cladogram from a character table, using an outgroup, and mark where each derived character arose. (Guide: Worked example 1 and Figure 2; Practice Q4)
  • I can count sequence differences between species and use the smallest counts to find sister pairs. (Guide: Worked example 2; Practice Q6)
  • I can calibrate a molecular clock from a dated split and use it to estimate another split, with units. (Guide: Worked example 2; Practice Q5)

Reasoning

  • I can judge which species are most closely related from the nodes, ignoring the order of the tips. (Guide: “Reading a tree”; Practice Q2)
  • I can explain how convergent evolution can make a body-form tree disagree with a molecular tree. (Guide: Worked example 2 (d); Practice Q6, Q7)
  • I can state the assumptions and limits of a molecular-clock date. (Practice Q5)
  • I can propose evidence that would test a tree, and state the result that would support it. (Practice Q7)

All ticked? Move on to Topic 7.10, Speciation, or return to the course roadmap.

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