AP Bio · Unit 7 Progress Check

AP Biology Unit 7 Progress Check: Natural Selection walkthrough.

AP Biology Unit 7 is Natural Selection, and College Board weights it at 13–20% of the exam’s multiple-choice section, the heaviest of the eight units. Progress Check 7 is the biggest one in the course: about 48 multiple-choice questions, split across two parts, plus two full-length free-response questions. College Board names both of them, and one is the only question on the AP Biology exam that asks you to construct a graph. Explanations only, never AP Classroom answer keys.

Updated September 2026Written by Mahmudul HasanFree · No signup

What is on the AP Biology Unit 7 Progress Check

College Board sets out what each Progress Check contains in its Course and Exam Description, and Unit 7 has the largest one in AP Biology. If you are working through the whole subject, we have every AP Biology Progress Check walkthrough, unit by unit.

The multiple-choice questions

College Board lists the AP Classroom Unit 7 Progress Check MCQ as roughly 48 questions delivered in two parts. That is roughly double the Unit 6 Progress Check, and only one other unit is split across two parts at all: Unit 2, at about 33. College Board prints the count as an approximation, so treat 48 as the scale rather than an exact promise.

The two free-response questions

There are two, and College Board names both: Interpreting and Evaluating Experimental Results with Graphing, and Analyze Data. Elsewhere in the same tables College Board flags shortened free-response questions as partial, and it does that on six other units. Neither of Unit 7’s two questions carries that marker, so both run full length.

How much the unit is worth

College Board weights Unit 7 at 13–20% of the multiple-choice section, which is the highest floor and the highest ceiling of the eight units. That figure describes Section I only. The free-response section is not weighted by unit at all: College Board spreads the four short free-response questions across four separate big ideas and four separate units.

The twelve topics College Board lists for Unit 7

Unit 7 is Natural Selection, and College Board divides it into twelve topics across about 19 to 21 class periods. The Progress Check draws on all of them.

7.1–7.3 Selection

Introduction to Natural Selection, Natural Selection, and Artificial Selection.

7.4 Population Genetics

Random change in allele frequencies: mutation, genetic drift, the bottleneck effect, the founder effect, and migration producing gene flow.

7.5 Hardy–Weinberg Equilibrium

p + q = 1 and p² + 2pq + q² = 1, with p and q the frequencies of the two alleles, plus the conditions a non-evolving population would need.

7.6 Evidence of Evolution

Geographical, geological, physical, biochemical and mathematical data; morphological homologies including vestigial structures; DNA nucleotide and protein amino acid sequences.

7.7–7.9 Ancestry and phylogeny

Common Ancestry, Continuing Evolution, and Phylogeny: cladograms, phylogenetic trees, shared derived characters, nodes, lineages and the out-group.

7.10–7.12 Speciation onward

Speciation, Variations in Populations, and Origins of Life on Earth: allopatric and sympatric speciation, pre-zygotic and post-zygotic isolating mechanisms, punctuated equilibrium and gradualism, divergent and convergent evolution, adaptive radiation.

College Board also notes where the unit connects outward. It tells students to recall the sources of genetic variation from Unit 5, which our AP Classroom Unit 5 Progress Check MCQ Answers AP Bio walkthrough covers in full. It also says the principles here carry into Unit 8 and ecology, picked up in our AP Classroom Unit 8 Progress Check MCQ Answers AP Bio walkthrough.

The multiple-choice questions: what each pattern tests

The multiple-choice section runs in two parts, and these patterns account for most of it.

Hardy–Weinberg calculation

Usually you are given q², the frequency of the recessive phenotype, which for a fully recessive trait is also the homozygous recessive genotype frequency. Take the square root for q, then p = 1 − q. The heterozygote frequency is 2pq.

Equilibrium conditions

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

Cladogram reading

Shared derived characters define clades and nodes mark common ancestors. Closeness on the page is not closeness in ancestry.

Trees versus cladograms

College Board draws the distinction explicitly: phylogenetic trees calibrate change over time using fossils or a molecular clock, and cladograms show no time scale.

Selection type

Directional, stabilizing or disruptive, identified from a graph of phenotype frequency. This is standard classroom vocabulary rather than College Board’s own wording, so expect the idea, not the labels.

Drift versus selection

College Board defines genetic drift as change in allele frequencies from a nonselective process in small populations. Selection is not random.

The two free-response questions

This is the part most Unit 7 guides get wrong, including ours until now. College Board does not leave the free response to guesswork: it names both questions on Progress Check 7, and it publishes what every part of each one is worth.

Part-level point values published by College Board in the AP Biology Course and Exam Description.

Interpreting and Evaluating Experimental Results with Graphing

This is the exam’s Question 2, worth nine points across four parts. Part A is one point for describing a biological concept or process. Part B is four points for constructing the appropriate graph from the data you are given. Part C is two points for analyzing data, performing calculations, stating a null hypothesis or predicting results. Part D is two points for making and justifying predictions.

Part B is the largest single part value anywhere in the AP Biology free-response section, and on its own it carries as much as Parts C and D put together. College Board describes it from two directions, and they do not quite agree: the exam structure puts four points on Part B, while its guidance on scoring graphs says up to three points are earned for a correctly constructed graph. Take the pair rather than either one alone. On any reading, the drawing is the biggest thing on this Progress Check.

How the graph is scored

College Board publishes what its Readers look for, which is unusual and worth more than any advice we could give. A graph earns credit on five fronts.

Pick the right kind of plot

The graph type has to suit the data you were handed. The prompt will tell you which graphing element it wants for that data set.

Label both axes, with units

Independent variable on the x-axis, dependent on the y-axis, units on both. If more than one condition appears, a legend has to say which line or bar is which.

Keep the intervals even

Equal spacing throughout. Mark any break in an axis, show whether the data actually start at the origin, and do not run the line past your last data point unless a dashed line flags it as a prediction.

Make the data readable

Points have to be easy to pick out, and error bars are required whenever the table gives you the standard error of the mean.

Trend lines where they belong

Appropriate on a scatter plot, or where one graph carries several sets of data.

One detail students lose time over: a title earns no point. College Board says so directly. It still recommends writing one, because it tells the Reader what was measured.

And this is what decides which one you should practice. Questions 1 and 2 share almost the same title and split their nine points differently: Question 1 runs 1-3-3-2 and has no graph-construction part at all, while Question 2 runs 1-4-2-2. Unit 6 gets Question 1. Unit 7 gets Question 2. A student who prepares for this Progress Check by grinding Hardy–Weinberg algebra is preparing for Part C, worth two of the nine points, and skipping the largest part on the question. For the full picture of how the section is built and scored, see our AP Biology FRQ guide.

Analyze Data

This is the exam’s Question 6, worth four points with one point on each of its four parts. Parts A and B ask you to describe data. Part C asks you to use the data to evaluate a hypothesis or prediction. Part D asks you to explain how the results relate to a larger biological principle. It is a short question, and every part is worth the same, so an unanswered part costs exactly as much as a wrong one.

Where students lose the most points

College Board names four of these itself, in the Course and Exam Description under Preparing for the AP Exam, and they are worth more than any list we could invent. Two more come from the way the questions are built.

Writing Lamarckian sentences

College Board asks for precision in how students write about evolution. Traits are not acquired through effort and passed on; variation already present is selected.

Using fitness as a buzzword

College Board names this directly: using a term like fitness without explaining the underlying concept. Fitness is reproductive success, and a free-response answer has to say so.

Saying organisms evolve

Natural selection acts on individuals; populations evolve. College Board flags the wording, and it matters on the free response.

Blurring the isolating mechanisms

College Board notes that students do not clearly separate the types of reproductive isolation that lead to speciation. Know which are pre-zygotic and which are post-zygotic.

Confusing p² with p

p² is the homozygous dominant genotype frequency; p is the allele frequency. College Board warns teachers to keep allele and genotype frequencies apart.

Reading cladograms by proximity

Relatedness comes from branch points, not from how close two tips sit on the page.

How to work through this unit

Start with the graph. It is the biggest single block of free-response points here, and College Board tells you in advance that it is coming. Practice drawing axes that carry labels and units, and plotting the data you are handed on them.

For the algebra, start from q². Square-root it for q, subtract from 1 for p, and the rest follows. You are not expected to memorize the equations: College Board prints both Hardy–Weinberg equations, and a chi-square table, on the equation sheet supplied with the exam. What you are expected to do is know when the model applies.

That last point is where College Board is more interesting than most study guides. Its own wording is that the Hardy–Weinberg conditions are never met in a real population, and that their value is as a null hypothesis. It asks for five things at once: a population large enough that chance alone does not shift the frequencies, no migration in or out, no new mutations, mating that happens at random, and no natural selection. So the useful question in a free-response answer is not whether the conditions hold, because they do not. It is which one is being violated, and what that tells you about the population.

When you have worked through the Progress Check, our AP Bio test score calculator converts a raw score into an approximate 1–5, and the AP Biology Review covers the exam format and a study plan.

Frequently asked questions

Quick answers, checked against College Board.

What does the AP Biology Unit 7 Progress Check cover?

Natural selection and evolution. College Board lists twelve topics for Unit 7. Five of them deal with selection and population genetics, ending at Hardy–Weinberg equilibrium; four with the evidence for evolution and common ancestry, ending at phylogeny; and three with speciation, variation inside populations, and how life began on Earth.

How many questions are on the Unit 7 Progress Check?

College Board’s Course and Exam Description lists roughly 48 multiple-choice questions, delivered in two parts, plus two free-response questions. It is the largest Progress Check in AP Biology. Only one other unit splits its multiple-choice section into two parts, Unit 2, and that one runs to about 33 questions. The count is published as an approximation.

Which free-response questions are on Progress Check 7?

College Board names both. One is Interpreting and Evaluating Experimental Results with Graphing, the exam’s nine-point Question 2, whose Part B is the graph you draw. The other is Analyze Data, a four-point question with one point on each of its four parts. Neither is marked as partial, so both run full length.

How do you solve a Hardy–Weinberg problem?

Start with the homozygous recessive genotype frequency, which is q². Take its square root to find q, then use p = 1 − q, and substitute into p² + 2pq + q² = 1. Both equations are printed on the equation sheet supplied with the exam.

What are the Hardy–Weinberg conditions?

Five have to hold at once: the population has to be large, nothing migrates in or out, no new mutations appear, mating is random, and natural selection is not acting. College Board also says these conditions are never met in practice, and that the model’s value is as a null hypothesis: a mismatch tells you 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.