AP Biology Unit 7 Topic 3: Evidence of evolution and common ancestry

What to Know

Shared structures and DNA similarities can indicate common ancestry.
Fossils show patterns of change and extinction across geologic time.
Biogeography helps explain why related organisms are found in particular places.
Always connect this topic back to the larger unit: Natural Selection.

Detailed Notes

Evidence of evolution and common ancestry belongs to Unit 7: Natural Selection. Evolution is supported by evidence from fossils, anatomy, embryos, molecular data, and geographic distribution. Treat the topic as a relationship between structure, process, evidence, and biological function instead of memorizing an isolated definition.

Key relationships: Shared structures and DNA similarities can indicate common ancestry. Fossils show patterns of change and extinction across geologic time. Biogeography helps explain why related organisms are found in particular places.

Model to use: Compare evidence types and rank which observations most strongly support common ancestry for a given group. A clear model should label the parts, show the direction of movement or information flow when relevant, and connect the diagram back to the biological outcome.

AP-style move: For evidence questions, describe the evidence and explain how it supports descent with modification rather than only naming it. Strong answers name the concept, apply it to the scenario, and explain the reasoning in complete sentences.

Key Vocabulary

Homologous structure

A structure shared due to common ancestry, even if functions differ.

Vestigial structure

A reduced structure inherited from ancestors that may have limited current function.

Molecular homology

Similarity in DNA, RNA, or protein sequences due to shared ancestry.

Fossil record

The collection of preserved remains and traces showing past life.

Biogeography

The study of how organisms are distributed across geographic areas.

Common ancestor

An ancestral population from which two or more lineages descend.

Quick Practice

How would you explain Evidence of evolution and common ancestry in one or two AP-style sentences?

Name the concept, apply it to a specific example or source, and explain the reasoning that connects the evidence to your answer.

Official Alignment

Reference and Attribution

Biology concept reference: Biology for AP Courses by OpenStax, Rice University. Access for free at OpenStax. Licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License. EduCompanion used this source as a conceptual reference and rewrote the study notes in original wording.