AP® Biology study guide: a printable PDF built from the College Board's official course and exam description, heaviest topics first.
Last updated 2026 · exam details checked against the College Board's published exam information in 2026
Real pages from the 54-page PDF.
One chapter for each area of the official course and exam description, heaviest topics first.
Multiple-choice questions taken from the guide's chapter quizzes: one from each of the ten heaviest areas. About 15 minutes, with every answer explained and a score by area. The exam's free-response questions aren't in this quiz: see how the exam works.
Answer: C. 210. q² = 45/500 = 0.09, so q = 0.3 and p = 0.7. Heterozygotes are 2pq = 2(0.7)(0.3) = 0.42, and 0.42 × 500 = 210 snails.
The trap: 245 is p² × 500 = 0.49 × 500, the expected number of homozygous dominant snails, not heterozygotes.
q² = 45/500 = 0.09, so q = 0.3 and p = 0.7. Heterozygotes are 2pq = 2(0.7)(0.3) = 0.42, and 0.42 × 500 = 210 snails.
The trap: 245 is p² × 500 = 0.49 × 500, the expected number of homozygous dominant snails, not heterozygotes.
Answer: D. Heat disrupted bonds that hold the enzyme's shape, changing its active site. Above its optimal temperature the enzyme begins to denature: heat breaks the hydrogen bonds and other interactions that hold its shape, so the active site no longer fits the substrate.
The trap: Slower molecules would explain a drop at low temperature. At higher temperatures molecules move faster, so collisions become more frequent, not less.
Above its optimal temperature the enzyme begins to denature: heat breaks the hydrogen bonds and other interactions that hold its shape, so the active site no longer fits the substrate.
The trap: Slower molecules would explain a drop at low temperature. At higher temperatures molecules move faster, so collisions become more frequent, not less.
Answer: B. Methionine–phenylalanine–glutamate. The mRNA is complementary to the template: 5′-AUG UUC GAA-3′, which codes for methionine, phenylalanine and glutamate.
The trap: Tyrosine–lysine–leucine comes from reading the template itself as if it were mRNA (UAC AAG CUU); codons are read on the complementary mRNA.
The mRNA is complementary to the template: 5′-AUG UUC GAA-3′, which codes for methionine, phenylalanine and glutamate.
The trap: Tyrosine–lysine–leucine comes from reading the template itself as if it were mRNA (UAC AAG CUU); codons are read on the complementary mRNA.
Answer: A. The target enzyme stays phosphorylated even when no hormone is present. Every step after the G protein depends on the G protein being active. If it is stuck on, cAMP is made, the kinase stays active and the target enzyme stays phosphorylated with or without the hormone.
The trap: Saying the hormone can no longer bind confuses the receptor with the G protein; the mutation is downstream of the receptor, so binding is unaffected.
Every step after the G protein depends on the G protein being active. If it is stuck on, cAMP is made, the kinase stays active and the target enzyme stays phosphorylated with or without the hormone.
The trap: Saying the hormone can no longer bind confuses the receptor with the G protein; the mutation is downstream of the receptor, so binding is unaffected.
Answer: B. 60 deer per year. dN/dt = rmax N((K − N)/K) = 0.4 × 600 × (200/800) = 0.4 × 600 × 0.25 = 60 deer per year.
The trap: 240 deer per year is the exponential rate, rmax N, with no adjustment for how close the population is to its carrying capacity.
dN/dt = rmax N((K − N)/K) = 0.4 × 600 × (200/800) = 0.4 × 600 × 0.25 = 60 deer per year.
The trap: 240 deer per year is the exponential rate, rmax N, with no adjustment for how close the population is to its carrying capacity.
Answer: D. Smooth endoplasmic reticulum. Steroid hormones are lipids, and the smooth ER is where cells make lipids, including steroids. Ribosomes and rough ER build proteins, which these cells secrete very little of.
The trap: Rough endoplasmic reticulum is tempting because it is also ER, but its ribosomes make proteins, and these cells secrete almost no protein.
Steroid hormones are lipids, and the smooth ER is where cells make lipids, including steroids. Ribosomes and rough ER build proteins, which these cells secrete very little of.
The trap: Rough endoplasmic reticulum is tempting because it is also ER, but its ribosomes make proteins, and these cells secrete almost no protein.
Answer: C. The rate of oxygen use by the seeds. The dependent variable is what is measured in response to the change: the rate at which the seeds use oxygen.
The trap: Temperature is what the student deliberately changed, so it is the independent variable.
The dependent variable is what is measured in response to the change: the rate at which the seeds use oxygen.
The trap: Temperature is what the student deliberately changed, so it is the independent variable.
Answer: A. A bar graph with one bar for each light color. Light color is a set of separate categories, and the dependent variable is a mean for each one, so a bar graph with error bars fits best.
The trap: A line graph implies a continuous independent variable with meaningful values between the points; there is nothing between "red" and "blue" on this axis.
Light color is a set of separate categories, and the dependent variable is a mean for each one, so a bar graph with error bars fits best.
The trap: A line graph implies a continuous independent variable with meaningful values between the points; there is nothing between "red" and "blue" on this axis.
Answer: C. χ² ≈ 2.67, below 3.84, so the null hypothesis is not rejected. Expected counts are 150 and 50. χ² = (140 − 150)²/150 + (60 − 50)²/50 = 0.67 + 2.00 = 2.67. With 1 degree of freedom the critical value is 3.84, and 2.67 is smaller, so the data are consistent with a 3:1 ratio.
The trap: χ² ≈ 2.38 comes from dividing by the observed counts instead of the expected counts; each term must be divided by the expected value.
Expected counts are 150 and 50. χ² = (140 − 150)²/150 + (60 − 50)²/50 = 0.67 + 2.00 = 2.67. With 1 degree of freedom the critical value is 3.84, and 2.67 is smaller, so the data are consistent with a 3:1 ratio.
The trap: χ² ≈ 2.38 comes from dividing by the observed counts instead of the expected counts; each term must be divided by the expected value.
Answer: A. Adhesion to the glass and cohesion among water molecules. Water molecules stick to the polar glass (adhesion) and pull neighboring water molecules along through hydrogen bonds (cohesion). In a narrow tube this pull lifts the water column higher.
The trap: Specific heat and heat of vaporization are real properties of water, but they describe how water absorbs heat, not how it climbs a surface.
Water molecules stick to the polar glass (adhesion) and pull neighboring water molecules along through hydrogen bonds (cohesion). In a narrow tube this pull lifts the water column higher.
The trap: Specific heat and heat of vaporization are real properties of water, but they describe how water absorbs heat, not how it climbs a surface.
The AP® Biology exam is from the College Board. It has 60 multiple-choice questions, plus 6 free-response questions. You get 90 minutes for multiple choice (3 hours in all); scientific or four-function calculator allowed. The score scale is 1–5 (AP® score scale; many U.S. colleges give credit for 3 and above). The guide has 11 chapters, one for each area of the official course and exam description; the heaviest is Natural Selection at 13–20%.
Source: official AP® Biology page and the official course and exam description. Last updated 2026.
11 chapters, heaviest first, with each area's official weight. The guide's chapters follow this order.
* Not units: skills tested inside every unit. Questions and Methods: questions about testable questions, hypotheses, variables and controls appear inside every unit, 8–14% of the multiple-choice section. Representing and Describing Data: graph and table questions appear inside every unit, 8–14% of the multiple-choice section. Statistical Tests and Data Analysis: calculation and statistics questions appear inside every unit, 8–14% of the multiple-choice section. These weights are a share of the same multiple-choice questions, so the weights add up to more than 100%.
Where to start: the 5 heaviest areas (marked in the map) carry about 42 of the 60 questions. The guide puts them first, so working front to back covers the most points earliest.
The 2 heaviest areas are open to read now. The full guide has a chapter for every area, each with all its terms, a quiz and an answer key.
Unit 7, the heaviest unit at 13–20%, explains how populations evolve: natural selection, random processes, Hardy–Weinberg, the evidence for evolution, phylogenetic trees and speciation. It ends with the origin of life: Earth formed about 4.6 billion years ago, and the earliest fossils are about 3.5 billion years old.
Key terms, with examples
What this area covers
Key people
| Charles Darwin | Set out the theory of evolution by natural selection in On the Origin of Species (1859). |
|---|
How the exam asks it
Many questions give a population scenario and ask which mechanism explains a change: selection when a trait affects survival and reproduction, drift when chance does the sorting, gene flow when individuals move. Hardy–Weinberg questions give a phenotype or genotype frequency and ask for allele or carrier frequencies (use the equation sheet). Tree questions ask which species are most closely related or which trait marks a branch. Speciation questions ask which barrier is acting or which pattern of change fits the evidence.
Common traps
Trap 1. Individuals don't evolve; populations do. Selection acts on individuals' phenotypes, but evolution shows up as changing allele frequencies in the population.
Trap 2. A drug doesn't create resistance. Resistant variants were already present; the drug killed the others and selected them.
Trap 3. Tips drawn close together on a tree aren't necessarily close relatives. Find the most recent node the two lineages share.
Memory trick
Hardy–Weinberg needs a big, closed, randomly mating population with no mutation and no selection.
Homologous = same origin; analogous = same job.
Unit 3 covers how cells capture and use energy: enzymes, the energy rules living things follow, photosynthesis and cellular respiration. Questions expect you to trace energy, electrons and protons through a process, not to recite every step.
Key terms, with examples
What this area covers
How the exam asks it
Many questions describe an enzyme graph in words (rate against temperature, pH or substrate) and ask why the rate changes. Others describe a blocked step, such as an inhibitor, a leaky membrane, darkness or a lack of oxygen, and ask what happens to ATP, NADPH, oxygen or carbon dioxide. The CED excludes memorizing the steps, molecules and enzyme names of the Calvin cycle, glycolysis and the Krebs cycle (ATP synthase is the exception), so focus on inputs, outputs, locations and the proton gradient.
Common traps
Trap 1. Enzymes lower activation energy; they don't add energy to a reaction, and they aren't used up by it.
Trap 2. Extra substrate overcomes a competitive inhibitor but not a noncompetitive one. Check what happens to the rate when substrate is high.
Trap 3. The oxygen released in photosynthesis comes from water, not from carbon dioxide; the carbon in the sugar comes from CO2.
Memory trick
OIL RIG: Oxidation Is Loss, Reduction Is Gain (of electrons).
Light reactions sit on the thylakoid stacks; the Calvin cycle swims in the stroma.
The exam has 60 multiple-choice questions, plus 6 free-response questions. The guide sorts the questions into 5 types; spot the type and you'll know what the question wants before you read the choices.
A short description of an organism, cell or process, then "which of the following best explains..." with four possible explanations.
A system is described, then one part is changed: a mutation, a drug, a removed species or a missing nutrient. You predict what happens next.
A diagram of a pathway, cell, food web, cladogram or graph (on the exam it is shown as an image), then a question about what one part shows or what the model predicts.
A short investigation, then a question about its testable question, null hypothesis, variables, controls or how to improve it.
A small table or a described graph, then a calculation (mean, rate, percent change, ratio, standard error, chi-square, Hardy–Weinberg, water potential) or a judgment about what the numbers show.
Pacing: 60 questions in 90 minutes, about 90 seconds a question.
Try the first 8 cards free. Read the term, say the definition out loud, then select the card to check yourself. Arrow keys move between cards.
Follow the steps, then enter your test date. The planner gives you a dated plan that starts with the heaviest areas and saves the last days for review.
Everything on this page is free with no account. The full guide is a PDF you keep.
| Study tool | This page | Full study guide ($5) |
|---|---|---|
| Chapters | A preview of 2 of 11 | All 11 |
| Terms explained | A sample from the open chapters | All 225, each with an example |
| Practice questions | 10 free questions | 59, with an answer key |
| Flashcards | 8 cards | All 225 terms on the self-check list |
| Study plan | Dated planner | 2-, 4- and 8-week plans |
| Cram sheet | — | 2 pages, for the night before |
| Format | Web page | 54-page PDF, printable |
We built one chapter for each area of the College Board's official course and exam description for AP® Biology, using its published weights to order the chapters and size the quizzes. Each chapter was written, then fact-checked against the official exam information in a separate review. The exam details were checked against the College Board's published exam information in 2026.
Sources: official AP® Biology page, official course and exam description. Last updated 2026.
AP® is a trademark registered by the College Board, which is not affiliated with, and does not endorse, this guide. TransferCredit.org is independent and not affiliated with the College Board. © 2026 UPI Globale Edu Inc.
Ready for the full AP® Biology guide? 54 pages, 225 terms, 59 practice questions and a 2-page cram sheet, $5.
Get the guide · $5