Phylogeny

Phylogeny is topic 7.9 of AP Biology, inside Natural Selection. This page works through three real practice questions on it, with the full reasoning behind each credited answer.

Practise this topic freeThe whole unit
42 questionsVisual Representations81% with a figure
Worked examples

Three real phylogeny questions

From the practice pool, not the mock papers — each with the reasoning that produces the answer.

81% of them come with a figure. Reading the graph or diagram correctly is most of the work here before any content knowledge applies.

Visual Representations · with figure

Based on Figure 1, which statement gives the strongest supported interpretation?

  1. AMarker A: An outgroup can help infer which character states are ancestral in a phylogenetic comparison.
  2. BMarker B: A derived character mapped after a branch point is expected in descendant lineages from that branch.
  3. CMarker C: Branch length may represent change
  4. DMarker D: C and D share the derived character through common ancestrycorrect
Why D is correct

Figure 1 shows two taxa joined at the most recent shared node before the third taxon splits from the lineage. Marker D: Taxa joined by the most recent shared node are interpreted as the closest relatives in the model. The figure does not mark an outgroup, a derived character, branch-length scale, bootstrap value, or parsimony comparison.

The evidence in the prompt matters before the topic label: "A cladogram shows a derived character appearing on the branch leading to species C and D, but not species A or B....". The supported answer is "Species C and D inherited the derived character from a recent common ancestor" because A derived character marked before the C-D split is inferred to be inherited by both C and D from their common ancestor. Distractors such as Species B is the ancestor of species C or All four species must be equally related to each other either ignore the stated pattern or name a related concept without matching the evidence.

Visual Representations · with figure

A student is using Figure 1 as evidence for a phylogenetic model. Which statement is supported?

  1. AMarker A: Branch length may represent change
  2. BMarker B: More recent common ancestry indicates closer relatednesscorrect
  3. CMarker C: An outgroup can help infer which character states are ancestral in a phylogenetic comparison.
  4. DMarker D: A derived character mapped after a branch point is expected in descendant lineages from that branch.
Why B is correct

Figure 1 shows two taxa joined at the most recent shared node before the third taxon splits from the lineage. Marker B: Taxa joined by the most recent shared node are interpreted as the closest relatives in the model. The figure does not mark an outgroup, a derived character, branch-length scale, bootstrap value, or parsimony comparison.

The evidence in the prompt matters before the topic label: "In a phylogenetic tree, species B and C share a more recent common ancestor with each other than either shares...". The supported answer is "Species B and C are more closely related to each other than either is to A" because Relatedness on a phylogenetic tree is based on recency of common ancestry. Distractors such as Species C must be the most complex species or Species A is the ancestor of species B either ignore the stated pattern or name a related concept without matching the evidence.

Visual Representations · with figure

Figure 1 shows a phylogenetic model. Which complete statement is best supported by the visual evidence?

  1. AMarker A: An outgroup can help infer which character states are ancestral in a phylogenetic comparison.
  2. BMarker B: A derived character mapped after a branch point is expected in descendant lineages from that branch.
  3. CMarker C: Branch length may represent change
  4. DMarker D: Shared recent node supports closer relatedness of Y and Zcorrect
Why D is correct

Figure 1 shows two taxa joined at the most recent shared node before the third taxon splits from the lineage. Marker D: Taxa joined by the most recent shared node are interpreted as the closest relatives in the model. The figure does not mark an outgroup, a derived character, branch-length scale, bootstrap value, or parsimony comparison.

The evidence in the prompt matters before the topic label: "A phylogenetic tree shows species X branching off before a node that later splits into species Y and Z. Which...". The supported answer is "Species Y and Z share a more recent common ancestor with each other than with X" because On a phylogenetic tree, more recent shared nodes indicate closer evolutionary relationships. Distractors such as Species X cannot share any DNA sequences with Y or Z or Species X is the parent of species Y either ignore the stated pattern or name a related concept without matching the evidence.

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Last reviewed 2026-08-28. Topic and unit names follow the College Board course framework. Question counts describe the PrepScore practice bank, not the exam.
Same unit
Natural Selection52 questionsPopulation Genetics29 questionsSpeciation26 questionsHardy-Weinberg Equilibrium23 questions

Work phylogeny until the reasoning is automatic.

Real AP questions with a full explanation on every answer, and a mistake bank that only clears when you get it right.

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