AP Biology · Unit 7: Natural Selection
7.9 Phylogeny
In short
The topic requires you to understand how phylogenetic trees and cladograms are constructed and interpreted to infer evolutionary relationships. You must know that these models represent testable hypotheses subject to revision based on new evidence. You need to distinguish between phylogenetic trees (which show the amount of change over time calibrated by fossils or a molecular clock) and cladograms (which do not show a time scale).
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What else do you need to know about Phylogeny?
The curriculum emphasizes that molecular data typically provide more accurate and reliable evidence than morphological traits. You must be able to identify nodes as the most recent common ancestor and understand the role of an out-group (the lineage least closely related to the remainder of the organisms). You should also understand that shared derived characters can be present in more than one lineage, indicating common ancestry.
Can you do these?
- I can explain how traits gained or lost during evolution, including shared derived characters and molecular data, are used to construct phylogenetic trees and cladograms, and identify the out-group.
- I can use phylogenetic trees and cladograms to illustrate speciation and identify the most recent common ancestor at the nodes.
- I can construct phylogenetic trees and cladograms from morphological similarities and from DNA and protein sequence similarities.
How is Phylogeny tested on the exam?
You are assessed on your ability to analyze visual representations of biological concepts, specifically phylogenetic trees and cladograms (Skill 2.D). Exam questions may require you to identify nodes representing the most recent common ancestor, define an out-group based on missing derived characters, and explain how separate lineages can evolve similar traits (e.g., through convergent evolution or similar selective pressures). Free-response questions, such as Question 5 in the provided exam information, ask you to analyze a cladogram, identify points of greatest genomic similarity, and explain how genome changes contribute to speciation. A common you error is failing to recognize that these models are hypotheses that can be revised, or confusing the time scale representation between phylogenetic trees and cladograms.
Free practice questions with full explanations, and instant marking of your free-response answers.
Phylogeny: common questions
What do you need to know about Phylogeny for AP Biology?
The topic requires you to understand how phylogenetic trees and cladograms are constructed and interpreted to infer evolutionary relationships. You must know that these models represent testable hypotheses subject to revision based on new evidence. You need to distinguish between phylogenetic trees (which show the amount of change over time calibrated by fossils or a molecular clock) and cladograms (which do not show a time scale).
How is Phylogeny tested on the AP Biology exam?
You are assessed on your ability to analyze visual representations of biological concepts, specifically phylogenetic trees and cladograms (Skill 2.D). Exam questions may require you to identify nodes representing the most recent common ancestor, define an out-group based on missing derived characters, and explain how separate lineages can evolve similar traits (e.g., through convergent evolution or similar selective pressures).
How do I know I have mastered Phylogeny?
Check you can do each of these: explain how traits gained or lost during evolution, including shared derived characters and molecular data, are used to construct phylogenetic trees and cladograms, and identify the out-group; use phylogenetic trees and cladograms to illustrate speciation and identify the most recent common ancestor at the nodes; construct phylogenetic trees and cladograms from morphological similarities and from DNA and protein sequence similarities.
Where does Phylogeny fit in AP Biology?
Phylogeny is topic 7.9 in Unit 7: Natural Selection of AP Biology.
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