exam guide
How to study for AP Biology, from unit tests to the May 3, 2027 exam
The prettysmart teamUpdated 9 min readthe short answer
Study AP Bio on two tracks: spaced flashcards for the vocabulary and processes, and timed free-response practice for the science skills, which are half your score. Start with Unit 7, Natural Selection (13–20% of the multiple choice), then Units 3 and 6. The exam is Monday, May 3, 2027.
Key takeaways
- The exam is 3 hours: 60 multiple-choice and 6 free-response questions, and each half is 50% of your score.
- Graphing calculators are banned in 2027: bring a four-function or scientific one, or use Desmos inside Bluebook.
- Flashcards are for terms and processes; experiments, graphs and data need timed practice.
- Skip what College Board rules out, like the Krebs cycle intermediates and the Gibbs free energy equation.
- Self-studying? Get an exam-only seat before schools order exams on November 13, 2026.
In this guide
- What’s on the AP Biology exam in May 2027
- Which units matter most
- What to memorize and what to practice
- What you can skip
- How to study for an AP Bio unit test
- What exam readers marked down in 2025
- A plan from now to May 3, 2027
- If you have one week, or two days
- Self-studying AP Bio
- How AP Bio scores look
- Flashcards
- Questions
- Sources
What’s on the AP Biology exam in May 2027
The exam takes 3 hours, split into two halves that each count for 50% of your score.
| Multiple choice | Free response | |
|---|---|---|
| Questions | 60, some in sets of 4 or 5 sharing a graph, table or passage | 6: 2 long and 4 short |
| Time | 1 hour 30 minutes | 1 hour 30 minutes |
| Share of score | 50% | 50% |
The six free-response questions always come in the same order:
| # | Type | Points |
|---|---|---|
| 1 | Interpreting and evaluating experimental results | 9 |
| 2 | Interpreting and evaluating experimental results, with a graph you build | 9 |
| 3 | Scientific investigation | 4 |
| 4 | Conceptual analysis | 4 |
| 5 | Analyzing a model or visual representation | 4 |
| 6 | Analyzing data | 4 |
Four things to know before you start:
- It’s hybrid digital. You answer the multiple choice in College Board’s Bluebook app and read the free-response questions there, but you handwrite your free-response answers in a paper booklet.
- Graphing calculators are banned in 2027. You can bring a four-function calculator (with square root) or a scientific nongraphing one, or use the Desmos scientific calculator inside Bluebook. Plenty of guides, and even College Board’s own older course documents, still say graphing calculators are allowed.
- You get a formula sheet, with chi-square, Hardy–Weinberg, standard error, water potential, population growth and more. Practice using it, not memorizing it.
- There’s no penalty for guessing. Your multiple-choice score is the number you got right.
The exam is on Monday, May 3, 2027, in the afternoon session, which starts at 12 p.m. local time at most U.S. schools. AP Human Geography is the same morning: see how to study for AP Human Geography.
Which units matter most
These weights are for the multiple-choice section. College Board doesn’t publish unit weights for the free response, but each of the four short questions covers a different unit.
| Unit | Topic | Share of multiple choice |
|---|---|---|
| 1 | Chemistry of Life | 8–11% |
| 2 | Cells | 10–13% |
| 3 | Cellular Energetics | 12–16% |
| 4 | Cell Communication and Cell Cycle | 10–15% |
| 5 | Heredity | 8–11% |
| 6 | Gene Expression and Regulation | 12–16% |
| 7 | Natural Selection | 13–20% |
| 8 | Ecology | 10–15% |
Unit 7 is the heaviest, and it also has the most topics. Units 3 and 6 come next. The deck at the end of this page covers Unit 7.
What to memorize and what to practice
Memorize with flashcards:
- Terms with their exact meaning. Gene versus allele, allele frequency versus phenotype, even protein versus proton: College Board’s own notes say students mix these up, and precise wording decides free-response points.
- Structure and function pairs. Students can name an organelle but not say what it does.
- The inputs, outputs and locations of pathways: photosynthesis, cellular respiration, fermentation.
- Process sequences: signal transduction, cell cycle checkpoints, transcription and translation.
- Definitions with conditions: the five Hardy–Weinberg conditions, the biological species concept, prezygotic versus postzygotic barriers.
Practice, because flashcards can’t do it for you:
- Designing experiments: variables, controls and null hypotheses.
- Building a graph from a table: axes, units, scale and error bars. It’s 4 of the 9 points on question 2.
- Reading data: trends, points, relationships.
- Calculations with the formula sheet: chi-square, Hardy–Weinberg, standard error, water potential.
- Claim, evidence and reasoning: the “predict and justify” parts appear in five of the six questions.
Why flashcards for the first list: practice testing and spaced practice were the only two of ten common techniques rated high utility in a major review, and rereading and highlighting were rated low (Dunlosky et al., 2013).
Testing beats rereading. In one well-known experiment, students who tested themselves on reading passages remembered 56% a week later, against 42% for students who restudied (Roediger and Karpicke, 2006).
What you can skip
College Board’s course description lists things that will not be on the exam. Students waste hours on them:
| Topic | You don’t need |
|---|---|
| Macromolecules (1.4–1.7) | The molecular structures of specific carbohydrates, lipids, nucleotides or amino acids |
| Cellular energy (3.3) | The Gibbs free energy equation |
| Photosynthesis and respiration (3.4–3.5) | The steps of glycolysis and the Krebs cycle, the names of the intermediates, or the full names of the electron carriers |
| Cell cycle (4.6) | Specific cyclin and CDK pairs or growth factors |
| DNA replication (6.2) | Enzyme names, except DNA polymerase, ligase, RNA polymerase, helicase and topoisomerase |
| Translation (6.4) | The genetic code, except the start codon AUG |
| Mutations (6.7) | Specific mutations and chromosome-number disorders |
| Biotechnology (6.8) | The details of each technique |
You also don’t need to memorize formulas; they’re on the sheet. Learn when to use each one.
College biology and the MCAT do test the steps the exam skips. If you’re headed there next, how to memorize the Krebs cycle puts all 8 steps, their enzymes and products in one table.
How to study for an AP Bio unit test
- Use the unit’s learning objectives in the course description as your checklist, and cross off anything on the skip list above.
- Turn the unit’s key ideas into flashcards as you go, not the night before.
- Review them in three or four short sessions spread across the week before the test.
- Do the unit’s AP Classroom Progress Check, or one free-response question on the unit, under time.
Unit 1, the usual first test, covers:
- Water’s polarity and hydrogen bonding, and what they cause (cohesion, adhesion, surface tension).
- The elements in each macromolecule.
- Dehydration synthesis versus hydrolysis.
- The monomers and polymers of carbohydrates, lipids, nucleic acids and proteins, including the four levels of protein structure.
What exam readers marked down in 2025
Every year College Board publishes a report on how students answered. The 2025 report is a list of points students could have kept:
- The four short free-response questions averaged 1.7 to 2.0 points out of 4: half marks at best.
- Few students could justify an experimental control; many just called it “a baseline”.
- Students wrote the same thing for “provide evidence” and “justify the claim”. Evidence is what the data show; justification uses biology to explain why.
- Evolution answers used “phenotype” and “gene frequency” as if they meant the same thing. They don’t.
Watch out: “Ribosomes make amino acids” was one common error. They don’t; they link amino acids into proteins.
A plan from now to May 3, 2027
| When | What to do |
|---|---|
| Now to mid-November | Self-studying? Get an exam-only seat before schools order on November 13, 2026. Everyone: after each class unit, turn it into flashcards and review for 15–20 minutes most days |
| December–January | Keep every finished unit in your daily review; do one released free-response question a week on units you’ve covered, and score it with the official guidelines |
| February | Rotate through all six question types; practice building graphs from tables; do chi-square and Hardy–Weinberg with the formula sheet open |
| March | Try the Bluebook test preview to learn the interface; do timed multiple-choice sets that mix units |
| April | Two full timed practice exams, two weeks apart; sort your misses by unit and by skill |
| May 1–2 | Light review only; check your calculator isn’t a graphing one |
Short sessions spread over days beat one long session. A meta-analysis of 317 experiments found that spacing study across days, rather than cramming it into one sitting, is extremely useful for long-term memory (Cepeda et al., 2006).
The catch is doing the 15 minutes every day. That’s what prettysmart is for: it locks the apps you pick, and a few flashcards open them again. We compared it with the other options in the best app blockers for studying and the best study apps for high school students.
Tip: Taking more than one AP exam? AP World History is on May 6, AP U.S. History on May 7 and AP Psychology on May 14: see how to study for AP World History, how to study for APUSH and how to study for AP Psychology.
If you have one week, or two days
One week out:
- Order the units: 7, 3 and 6 first, then 4 and 8, then 1, 2 and 5.
- Each day: review yesterday’s cards first, add one new unit’s cards, do one timed free-response question of a different type, and 15 mixed multiple-choice questions.
- Day 6: one full timed section.
- Day 7: review lightly and sleep.
Two days out:
- Read the formula sheet once, so nothing on it is new on the day.
- Learn the command words: identify, describe, explain, justify, and the difference between a claim, evidence and reasoning.
- Do two or three short recall sessions on your Unit 7, 3 and 6 cards, hours apart, instead of rereading notes. In the same experiment as above, testing beat restudying even when the final test came two days later.
- Nothing new the night before.
Self-studying AP Bio
You can take the exam without taking the course.
- Sign up through a school. Join an exam-only section with a code from the AP coordinator at the school where you’ll test. If your school doesn’t offer AP Biology, call another school’s coordinator early.
- Deadline and fee: schools order exams by November 13, 2026, and the exam costs $99 in the U.S.
- The hard part on your own is the free response, which is built on lab-style experimental design and data, so start the six question types early.
How AP Bio scores look
| Year | 5 | 4 | 3 | 3 or higher |
|---|---|---|---|---|
| 2026 | 15% | 25% | 31% | 71% |
| 2025 | 18.9% | 24.1% | 27.4% | 70.4% |
| 2024 | 16.8% | 23.1% | 28.4% | 68.3% |
Heading for nursing or pre-med after AP Bio? College anatomy and physiology is less about experiments and more about naming structures and predicting what the body does next. Here is how to study for anatomy and physiology, including the timed lab practical.
Flashcards: AP Biology Unit 7: Natural Selection
71 cards, each checked against this guide's sources. Tap a card to see the answer.
AP Biology Unit 7 flashcards: Natural Selection: study them one at a time
1What is evolution in the context of population genetics?
A change in allele frequencies in a population over successive generations.
2According to Darwin's theory of natural selection, what does competition for limited resources lead to?
Differential survival: individuals with more favorable phenotypes are more likely to survive and produce more offspring, passing those traits on.
3What is differential reproductive success?
The phenomenon where individuals with traits better suited to the environment survive and produce more viable offspring.
4How is evolutionary fitness measured?
By reproductive success: an organism's contribution of offspring, and so of its alleles, to the next generation.
5_____ acts directly on an individual's phenotype, but it is populations that evolve over time.
Natural selection
6Natural selection acts directly on an individual's phenotype, but it is _____ that evolve over time.
populations
7Does natural selection act directly on genotypes or on phenotypes?
On phenotypes: it acts on phenotypic variation in a population. Allele frequencies change as a result.
8What is an adaptation in evolutionary biology?
A heritable trait that enhances an organism's ability to survive and reproduce in a specific environment.
9Can the same allele help in one environment and hurt in another? Why?
Yes. Selective pressures differ between environments, so an allele that is adaptive in one can be harmful in another.
10What is directional selection?
Natural selection that favors individuals at one extreme phenotypic range over others.
11What is stabilizing selection?
Natural selection that favors intermediate variants by acting against extreme phenotypes.
12What is disruptive selection?
Natural selection that favors individuals at both phenotypic extremes over intermediate phenotypes.
Show the other 59 cards
13What is artificial selection?
The selective breeding of domesticated plants and animals by humans to encourage desirable phenotypic traits.
14Which random process adds new genetic variation to a population?
Mutation. It supplies the variation that natural selection acts on.
15What is genetic drift?
A change in the allele frequencies of a population due to chance events.
16In what size population does genetic drift have the strongest effect?
Small populations.
17What is the bottleneck effect?
A type of genetic drift that happens when a population is cut to a small number of individuals for at least one generation (for example, by a natural disaster).
18What is the founder effect?
A type of genetic drift that happens when a few individuals are separated from the rest of the population; allele frequencies in the new population follow the founders' genes.
19Why can genetic drift make a small population diverge from other populations of its species?
Chance changes in allele frequency are biggest in small populations, so its allele frequencies can drift away from the others'.
20What is gene flow?
The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes.
21What does gene flow between two populations do to their chance of becoming separate species?
It lowers it: gene flow keeps the populations from diverging into separate species.
22What is the evidence that a population is evolving?
A change in its allele frequencies over time.
23In the Hardy–Weinberg equation p + q = 1, what does p represent?
The frequency of one of the two alleles (by convention, the dominant allele).
24In the Hardy–Weinberg equation p + q = 1, what does q represent?
The frequency of the other allele (by convention, the recessive allele).
25In the Hardy–Weinberg equation p2 + 2pq + q2 = 1, which term represents the frequency of heterozygous individuals?
2pq
26In the Hardy–Weinberg equation p2 + 2pq + q2 = 1, which term represents the frequency of homozygous dominant individuals?
p2
27In the Hardy–Weinberg equation p2 + 2pq + q2 = 1, which term represents the frequency of homozygous recessive individuals?
q2
28Name the five conditions required for a population to maintain Hardy–Weinberg equilibrium.
No mutations, random mating, no natural selection, extremely large population size, and no gene flow.
29The Hardy–Weinberg conditions are never met in nature. Why is the model still useful?
It is a null hypothesis: if allele frequencies change, at least one condition is being violated, so the population is evolving.
30If allele frequencies in a population change from one generation to the next, the population is violating _____ and undergoing evolution.
Hardy–Weinberg equilibrium
31If allele frequencies in a population change from one generation to the next, the population is violating Hardy–Weinberg equilibrium and undergoing _____.
evolution
32A population is in Hardy–Weinberg equilibrium and 16% of individuals show the recessive phenotype. What are q and p?
q² = 0.16, so q = 0.4 and p = 1 − 0.4 = 0.6.
33In that population (q = 0.4, p = 0.6), what fraction of individuals is heterozygous?
2pq = 2 × 0.6 × 0.4 = 0.48, or 48%.
34If 9% of a population shows the recessive phenotype, why is q not 0.09?
0.09 is q², a genotype frequency. The allele frequency is q = √0.09 = 0.3.
35Name the 3 ways fossils can be dated in AP Biology.
The age of the rocks the fossil is found in, the rate of decay of isotopes such as carbon-14, and geographical data.
36What are homologous structures?
Anatomical features that share a common evolutionary origin despite differences in current function.
37What are analogous structures?
Features that perform similar functions but evolved independently due to convergent evolution, not shared ancestry.
38What is convergent evolution?
The independent evolution of similar features in distinct evolutionary lineages due to similar selective pressures.
39What is a vestigial structure?
A remnant feature that served an important function in an organism's ancestors but has reduced or no function today.
40Which usually gives more accurate and reliable evidence for evolutionary relationships: molecular data or morphological traits?
Molecular data: comparisons of DNA nucleotide sequences and protein amino acid sequences.
41Name the 3 pieces of evidence that all eukaryotes share a common ancestor.
Membrane-bound organelles, linear chromosomes, and genes that contain introns.
42Give 2 examples showing that evolution is still happening.
Resistance to antibiotics, pesticides, herbicides or chemotherapy drugs, and pathogens evolving to cause emergent diseases.
43Why does using an antibiotic make resistant bacteria more common?
Bacteria that already carry resistance survive and reproduce while susceptible ones die, so the resistance allele's frequency rises.
44What is a phylogenetic tree?
A diagram that represents a hypothesis about the evolutionary history and relationships of a group of organisms.
45What does a phylogenetic tree show that a cladogram does not?
The amount of change over time, calibrated by fossils or a molecular clock. A cladogram shows relationships, not a time scale.
46Are phylogenetic trees and cladograms facts or hypotheses?
Hypotheses: they can be tested and are revised as new evidence comes in.
47On a phylogenetic tree, what does a branch point (node) represent?
The most recent common ancestor of the evolutionary lineages that diverge from that point.
48On a cladogram, the _____ is the lineage least closely related to all the other organisms shown.
outgroup
49What is a sister taxon?
One of two lineages that stem from the same branch point; the pair shares an immediate common ancestor that no other group shares.
50What is a monophyletic group (clade)?
A group composed of an ancestral species and all of its descendants.
51What is a shared derived character?
A trait that evolved in a common ancestor and is shared by its descendants but not by earlier lineages, such as hair in humans and rabbits but not lizards. It marks common ancestry.
52What does the principle of maximum parsimony state when constructing a phylogenetic tree?
The tree that needs the fewest evolutionary changes to explain the evidence is the most likely one.
53According to the biological species concept, what defines a species?
A group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring.
54When does speciation occur?
When two populations become reproductively isolated from each other.
55What is allopatric speciation?
Speciation that occurs when populations are geographically separated from one another.
56What is sympatric speciation?
Speciation that occurs in populations that live in the same geographic area.
57What is a prezygotic reproductive barrier?
An isolating mechanism that prevents mating or fertilization between different species.
58What is temporal isolation?
A prezygotic barrier in which species breed during different seasons, times of day, or years.
59What is behavioral isolation?
A prezygotic barrier in which specific courtship rituals or behaviors prevent interbreeding.
60What is mechanical isolation?
A prezygotic barrier where morphological differences prevent successful copulation.
61What is gametic isolation?
A prezygotic barrier where sperm of one species cannot fertilize the eggs of another species.
62What is a postzygotic reproductive barrier?
A mechanism that prevents hybrid zygotes from developing into viable, fertile adults.
63What is hybrid sterility?
A postzygotic barrier where the hybrid offspring develops into a viable adult but cannot produce functional gametes.
64What is punctuated equilibrium?
A model in which evolution happens rapidly after a long period of stasis.
65What is gradualism in the context of evolutionary tempo?
A model in which evolution happens slowly, through small changes over hundreds of thousands or millions of years.
66What is divergent evolution?
Adaptation to new habitats that leads related populations to become phenotypically different.
67_____ is the rapid evolution of many diversely adapted species from a common ancestor upon introduction to novel environmental niches.
Adaptive radiation
68Why are populations with little genetic diversity at greater risk of decline or extinction?
They are less likely to contain individuals that can withstand a new environmental pressure, such as a disease outbreak.
69About how old is Earth?
About 4.6 billion years old.
70When did Earth become hospitable to life, and how old is the earliest fossil evidence of life?
It was too hostile for life until about 3.9 billion years ago; the earliest fossils date to about 3.5 billion years ago.
71What does the RNA world hypothesis propose?
That RNA could have been the earliest genetic material, copied by base-pairing before genetically encoded proteins acted as catalysts.
Studying in Anki or Quizlet?
- Copy all the cards, or download the .txt.
- Quizlet: paste them into its import box. It reads Tab between term and definition.
- Anki: File, then Import, and pick the .txt file.
Questions people ask
Is AP Bio hard?
College Board describes it as equivalent to a two-semester introductory college biology course for biology majors, and recommends high school biology and chemistry first. In 2026, 71% of students scored 3 or higher and 15% scored a 5.
When is the AP Bio exam in 2027?
Monday, May 3, 2027, in Session 2, the afternoon slot, which starts at 12 p.m. local time at most U.S. schools. The late-testing date is Wednesday, May 19, 2027.
Can you use a graphing calculator on the AP Bio exam?
Not in 2027. College Board's 2027 policy allows a four-function calculator (with square root) or a scientific, nongraphing one, plus the Desmos scientific calculator built into Bluebook. Many older guides still say graphing calculators are fine.
How many questions are on the AP Bio exam?
60 multiple-choice questions in 90 minutes and 6 free-response questions (2 long, 4 short) in 90 minutes, each section worth half your score.
Is the AP Bio exam digital?
Partly. You answer the multiple-choice questions in the Bluebook app and read the free-response questions there too, but you handwrite your free-response answers in a paper booklet.
Can you self-study AP Bio?
Yes. You can take the exam without the course by joining an exam-only section through the AP coordinator at the school where you'll test. Schools order exams by November 13, 2026, and the fee is $99 in the U.S. The hard part alone is the free response, which is built on experimental design and data.
Is AP Bio harder than AP Chem?
Pass rates are close: in 2026, 71% of AP Biology and 75% of AP Chemistry students scored 3 or higher, and 15% of each scored a 5. Pass rates reflect who takes each exam, so they don't settle which is harder.
Sources
- AP Biology Course and Exam Description, effective fall 2025, College Board
- Biology 2e, 18.2 Formation of New Species, OpenStax
- Biology 2e, 20.2 Determining Evolutionary Relationships, OpenStax
- AP Biology Exam, College Board
- 2027 AP Exam Dates, College Board
- AP Exams Calculator Policy (update for 2027), College Board
- AP Biology Equations and Formulas sheet, College Board
- Chief Reader Report: 2025 AP Biology Free-Response Questions, College Board
- AP Biology score distributions, College Board
- Ordering exams for students who don't attend your school, College Board
- 2027 AP Exam Fees, College Board
- Improving Students' Learning With Effective Learning Techniques (Dunlosky et al., 2013), Psychological Science in the Public Interest
- Test-Enhanced Learning (Roediger and Karpicke, 2006), Psychological Science
- Distributed Practice in Verbal Recall Tasks (Cepeda et al., 2006), Psychological Bulletin