AP Biology Unit 7 Topic 4: Phylogeny

What to Know

Identify the system, surroundings, and scale before explaining a process.
Use diagrams, graphs, and tables as evidence rather than decoration.
For quantitative questions, keep units visible from the setup through the final answer.
Always connect this topic back to the larger unit: Natural Selection.

Detailed Notes

Phylogeny belongs to Natural Selection, so study it as part of a larger scientific system rather than as a stand-alone fact. Start by identifying what is being described, what is changing, and what evidence would let you defend a claim.

In AP Biology, strong answers usually connect a visible pattern to an underlying mechanism. That means explaining not only what happens, but why it happens at the particle, organism, environmental, or system level.

For AP-style questions, expect this topic to appear with graphs, diagrams, data tables, experiments, or written scenarios. Your job is to describe the evidence, apply the correct concept, and explain the reasoning that connects them.

Key Vocabulary

Natural selection

A mechanism of evolution in which traits that improve reproductive success become more common.

Fitness

An organism's relative ability to survive and reproduce in a particular environment.

Allele frequency

How common an allele is in a population.

Phylogeny

A hypothesis about evolutionary relationships among organisms.

Speciation

Formation of new species over time.

Quick Practice

How would you explain Phylogeny 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.