AP Bio · Unit 7 Progress Check

AP Biology Unit 7 Progress Check Natural Selection walkthrough.

AP Biology Unit 7 covers natural selection and evolution, and the Unit 7 Progress Check MCQ leans heavily on Hardy–Weinberg and phylogenetic trees. This walkthrough explains what the questions test, the conditions students forget, and how to reason through them. Explanations only — we never publish AP Classroom answer keys.

Updated August 2026Written by Mahmudul HasanFree · No signup

What Unit 7 covers

Unit 7 is Natural Selection. Natural selection is roughly 13–20% of the AP Biology exam — the single heaviest unit in the course.

Mechanisms of evolution

Natural selection, genetic drift, gene flow, mutation, and non-random mating.

Hardy–Weinberg equilibrium

p + q = 1 and p² + 2pq + q² = 1, plus the five conditions required.

Evidence for evolution

Fossils, homologous and analogous structures, molecular and biogeographic evidence.

Phylogenetic trees

Reading cladograms, shared derived characters, and common ancestry.

Speciation

Allopatric and sympatric speciation and reproductive isolation.

Origin of life

Early Earth conditions and the evidence for early cellular life.

The Progress Check MCQ: what each question type tests

These are the question patterns that recur on this Progress Check, and what each one is really asking.

Hardy–Weinberg calculation

Usually you are given q² (the recessive phenotype). Take the square root to get q, then p = 1 − q.

Equilibrium conditions

Asked which condition is violated. Any violation means the population is evolving.

Cladogram reading

Shared derived characters define clades. Closeness on the page is not closeness in ancestry.

Selection type

Directional, stabilising, or disruptive — identify which from a graph of phenotype frequency.

Drift versus selection

Drift is random and strongest in small populations; selection is non-random and adaptive.

The Progress Check FRQ

Unit 7 free response commonly asks for a Hardy–Weinberg calculation followed by an interpretation. Points come from showing the algebra, stating whether the population is in equilibrium, and — the part most often skipped — explaining which condition is being violated and what that implies biologically.

Where students lose the most points

Using Hardy–Weinberg without checking the conditions

All five must hold for equilibrium. Applying the equations blindly loses the reasoning points.

Confusing p² with p

p² is the homozygous dominant frequency; p is the allele frequency. Take the square root carefully.

Reading cladograms by proximity

Relatedness is determined by branch points, not by how close two tips sit on the page.

Calling genetic drift a form of selection

Drift is random change; selection is differential survival based on fitness.

Saying organisms evolve

Populations evolve, individuals do not. The wording matters on the free response.

How to work through this unit

On any Hardy–Weinberg question, start from the recessive phenotype — that is q². Square-root it for q, subtract from 1 for p, and everything else falls out.

Once you have finished the Progress Check, put your raw score into our AP Biology Calculator to see roughly where that pace puts you on the 1–5 scale, and use the AP Biology Review for the full exam format and study plan.

Frequently asked questions

Quick answers — written by humans, not a chatbot.

What does the AP Biology Unit 7 Progress Check cover?

Natural selection and evolution: mechanisms of evolution, Hardy–Weinberg equilibrium and its conditions, evidence for evolution, phylogenetic trees, speciation, and the origin of life.

How do you solve a Hardy-Weinberg problem?

Start with the recessive phenotype frequency, which is q squared. Take its square root to find q, then use p = 1 minus q, and substitute into p squared plus 2pq plus q squared.

What are the five Hardy-Weinberg conditions?

No mutation, no gene flow, no natural selection, random mating, and a very large population. If any is violated, the population is evolving.

Do you publish AP Biology Unit 7 answer keys?

No. We publish walkthroughs of the reasoning and the common mistakes rather than raw AP Classroom answers.