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AP Bio

AP Biology

From water molecules to whole ecosystems, practiced the way the exam asks: read the data, design the test, justify the claim.

Category
Sciences
Units
8 units
Exam
Exam May 3, 2027 (in 218 days)
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What the course covers

A full introductory college biology course in eight units, from the chemistry of life through cells, energy, signaling, heredity, gene expression, evolution, and ecology. The AP exam rewards far more than recall: most points go to reading experiments (identify the variables, the controls, the null hypothesis), working with data (graph it with error bars, calculate a rate, a percent change, an allele frequency, or a chi-square), interpreting models (pathway diagrams, cladograms, pedigrees), and making and justifying predictions when part of a biological system is disrupted. Every unit here trains those moves on original scenarios. The exam is 60 multiple-choice questions and 6 free-response questions in 3 hours, with a calculator and an equations sheet allowed throughout.

8 units, with exam weights

  1. Unit 1

    Chemistry of Life

    8-11% of examFree
    Why water behaves the way it does and how four families of macromolecules are built, broken, and shaped for their jobs. The unit sets up the structure determines function reasoning the whole course runs on: hydrogen bonding explains cohesion and heat capacity, directionality (5′5' to 3′3') explains how nucleic acids are copied, and R-group chemistry explains how a protein folds.
    7 topics
    1. 1.1Structure of Water and Hydrogen Bonding
    2. 1.2Elements of Life
    3. 1.3Introduction to Macromolecules
    4. 1.4Carbohydrates
    5. 1.5Lipids
    6. 1.6Nucleic Acids
    7. 1.7Proteins

  2. Unit 2

    Cells

    10-13% of exam
    How cell structures do their jobs and how membranes control what enters and leaves. The unit moves from organelles and the endomembrane system through surface-area-to-volume limits, membrane structure, passive and active transport, tonicity and water potential, and the evolutionary origin of compartmentalization. Expect calculations of surface-area-to-volume ratio and water potential, and prediction questions about cells in hypertonic and hypotonic solutions.
    10 topics
    1. 2.1Cell Structure and Function
    2. 2.2Cell Size
    3. 2.3Plasma Membrane
    4. 2.4Membrane Permeability
    5. 2.5Membrane Transport
    6. 2.6Facilitated Diffusion
    7. 2.7Tonicity and Osmoregulation
    8. 2.8Mechanisms of Transport
    9. 2.9Cell Compartmentalization
    10. 2.10Origins of Cell Compartmentalization

  3. Unit 3

    Cellular Energetics

    12-16% of exam
    How enzymes speed reactions and how cells capture energy from light and release it from food. The unit covers enzyme-substrate specificity, denaturation, temperature and pH optima, competitive and noncompetitive inhibition, the thermodynamics of living order, and the big-picture flow of photosynthesis and cellular respiration: electron transport chains, proton gradients, ATP synthase, and fermentation. Named intermediates and enzymes (other than ATP synthase) are excluded; the exam tests where energy goes and what happens when a step is blocked.
    5 topics
    1. 3.1Enzymes
    2. 3.2Environmental Impacts on Enzyme Function
    3. 3.3Cellular Energy
    4. 3.4Photosynthesis
    5. 3.5Cellular Respiration

  4. Unit 4

    Cell Communication and Cell Cycle

    10-15% of exam
    How cells send and receive signals, turn a signal into a response, keep conditions stable with feedback, and control when they divide. The exam loves disruption questions here: a mutated receptor, a blocked kinase, a drug that mimics a ligand, a checkpoint that fails. Students must trace the pathway from ligand to response and predict what changes downstream.
    6 topics
    1. 4.1Cell Communication
    2. 4.2Introduction to Signal Transduction
    3. 4.3Signal Transduction Pathways
    4. 4.4Feedback
    5. 4.5Cell Cycle
    6. 4.6Regulation of Cell Cycle

  5. Unit 5

    Heredity

    8-11% of exam
    How meiosis and fertilization pass chromosomes to the next generation and generate variation, and how traits are inherited. The unit runs from meiosis versus mitosis through Mendel's laws, probability, pedigrees, and chi-square tests to linked and sex-linked genes, incomplete dominance, codominance, pleiotropy, non-nuclear inheritance, and environmental effects on phenotype. Calculation-heavy: expect Punnett and probability problems, map distances, and chi-square with the table on the equations sheet.
    5 topics
    1. 5.1Meiosis
    2. 5.2Meiosis and Genetic Diversity
    3. 5.3Mendelian Genetics
    4. 5.4Non-Mendelian Genetics
    5. 5.5Environmental Effects on Phenotype

  6. Unit 6

    Gene Expression and Regulation

    12-16% of exam
    How DNA is copied, how its information becomes RNA and protein, how cells control which genes are on, how mutations change phenotypes, and how biotechnology reads and edits DNA. The unit is the mechanical core of heredity and evolution: codon tables, operons, transcription factors, epigenetics, small regulatory RNAs, mutation types, gel electrophoresis, and PCR. Expect data from gels, expression experiments, and knockouts.
    8 topics
    1. 6.1DNA and RNA Structure
    2. 6.2DNA Replication
    3. 6.3Transcription and RNA Processing
    4. 6.4Translation
    5. 6.5Regulation of Gene Expression
    6. 6.6Gene Expression and Cell Specialization
    7. 6.7Mutations
    8. 6.8Biotechnology

  7. Unit 7

    Natural Selection

    13-20% of exam
    The heaviest-weighted unit: how natural selection, artificial selection, and random processes change populations; how to detect evolution with Hardy–Weinberg; the evidence for evolution and common ancestry; how to read phylogenetic trees and cladograms; how species form and go extinct; why genetic diversity matters; and how life may have begun. Evolutionary reasoning also appears in FRQs set in every other unit.
    12 topics
    1. 7.1Introduction to Natural Selection
    2. 7.2Natural Selection
    3. 7.3Artificial Selection
    4. 7.4Population Genetics
    5. 7.5Hardy–Weinberg Equilibrium
    6. 7.6Evidence of Evolution
    7. 7.7Common Ancestry
    8. 7.8Continuing Evolution
    9. 7.9Phylogeny
    10. 7.10Speciation
    11. 7.11Variations in Populations
    12. 7.12Origins of Life on Earth

  8. Unit 8

    Ecology

    10-15% of exam
    How organisms respond to their environment and each other, how energy flows and matter cycles through ecosystems, how populations grow and are limited, how communities are structured, and how biodiversity, invasive species, human activity, and geological events change ecosystems. Calculation-heavy: population growth rates, logistic growth, Simpson's Diversity Index, and trophic energy transfers.
    7 topics
    1. 8.1Responses to the Environment
    2. 8.2Energy Flow Through Ecosystems
    3. 8.3Population Ecology
    4. 8.4Effect of Density on Populations
    5. 8.5Community Ecology
    6. 8.6Biodiversity
    7. 8.7Disruptions in Ecosystems

The exam, part by part

3 parts, 3 h in all.

  • Section I: Multiple Choice

    Questions
    60
    Time
    1 h 30 min
    Weight
    50%

    Calculator allowed

    Format details

    Four answer choices (A-D). A mix of discrete items and stimulus-based sets of typically 4-5 questions that share a data table, graph, diagram, model, or experimental description. All six science practices are tested; published practice weights are Concept Explanation 25-33%, Visual Representations 16-24%, Questions and Methods 8-14%, Representing and Describing Data 8-14%, Statistical Tests and Data Analysis 8-14%, Argumentation 20-26%. Unit weights (below) apply to this section only. Answered on screen in Bluebook.

  • Section II, Questions 1-2: Long Free Response

    Questions
    2
    Time
    50 min
    Weight
    26.5%

    Calculator allowed

    Format details

    Task types: Interpreting and Evaluating Experimental Results, Interpreting and Evaluating Experimental Results with Graphing

    One of each long type, 9 points each, about 25 minutes each (recommended pacing; Section II is one 90-minute block and students may move between questions). Both present an authentic experiment with data; Question 2 always requires constructing a graph (bar, line, or scatter, with error bars when given) on a printed template. College Board publishes only the 50% weight for all of Section II; the 26.5 / 23.5 split here is proportional to raw points (18 of 34).

  • Section II, Questions 3-6: Short Free Response

    Questions
    4
    Time
    40 min
    Weight
    23.5%

    Calculator allowed

    Format details

    Task types: Scientific Investigation, Conceptual Analysis, Analyze Model or Visual Representation, Analyze Data

    One of each short type in this fixed order (Q3 Scientific Investigation, Q4 Conceptual Analysis, Q5 Analyze Model or Visual Representation, Q6 Analyze Data), 4 points each (one point per part A-D), about 10 minutes each. Each short question focuses on a different big idea and a different unit.

How the 1 to 5 score is set

Section I (60 multiple-choice questions) and Section II (6 free-response questions: two 9-point long questions and four 4-point short questions, 34 raw points) each count for 50% of the score. There is no penalty for wrong multiple-choice answers. Free-response points are awarded point by point against a scoring guideline that lists acceptable answers for each part; each point is independent, answers must be written in sentences (a diagram or bulleted list alone earns nothing), and only the first answer given is scored when a prompt asks for one. The weighted composite is converted to the 1-5 AP scale with cut scores set each year.

What you bring and get

Students receive the AP Biology Equations and Formulas reference sheet throughout the exam (printed and in Bluebook): statistics (mean, standard deviation, standard error, chi-square with a critical-value table), laws of probability, Hardy–Weinberg equations, metric prefixes, rate and population growth equations (exponential and logistic), Simpson's Diversity Index, water and solute potential, and surface area and volume formulas. A four-function, scientific, or graphing calculator is allowed on both sections (an approved handheld or the calculator built into Bluebook). The exam is hybrid digital: multiple choice is answered in Bluebook; free-response questions are shown in Bluebook and answered by hand in a paper booklet, including the graph for Question 2 on a printed grid template.

Skills the exam scores

  • SP1Concept Explanation

    Explain biological concepts and processes presented in writing. 1.A describe a concept or process; 1.B explain it; 1.C explain it in an applied context. 25-33% of multiple choice; Part A of FRQs 1-5 is a 1.A point.

  • SP2Visual Representations

    Analyze visual representations of concepts and processes. 2.A describe characteristics of a visual representation; 2.B explain relationships between characteristics of a model; 2.C explain how a model relates to larger principles, processes, or theories; 2.D represent relationships within a model (diagrams, flowcharts, mathematical models). 16-24% of multiple choice; the focus of FRQ 5.

  • SP3Questions and Methods

    Determine scientific questions and methods. 3.A identify or pose a testable question; 3.B state the null hypothesis or predict results; 3.C identify procedures that fit the question (independent and dependent variables, appropriate controls and why they are appropriate); 3.D propose a new investigation from an evaluation of the design or evidence. 8-14% of multiple choice; the focus of FRQs 1 and 3.

  • SP4Representing and Describing Data

    Represent and describe data. 4.A construct a graph (bar, histogram, line, log scale, dual y, scatter, box and whisker, pie) with the right type, labeled axes with units and a legend, sensible scaling, accurate points and error bars, and a trend line when appropriate; 4.B describe data: specific points, trends and patterns, relationships between variables. 8-14% of multiple choice; the focus of FRQs 2 and 6.

  • SP5Statistical Tests and Data Analysis

    Perform statistical tests and calculations to analyze and interpret data. 5.A calculate (equations in the course, means, rates, ratios, percentages and percent change); 5.B use confidence intervals and error bars to judge whether means differ; 5.C perform a chi-square test; 5.D use data to evaluate a hypothesis, including rejecting or failing to reject the null. 8-14% of multiple choice; calculations appear in FRQs 1 and 2, and FRQ 6 evaluates a hypothesis.

  • SP6Argumentation

    Develop and justify scientific arguments using evidence. 6.A make a claim; 6.B support a claim with evidence; 6.C provide reasoning that connects evidence to biological theory; 6.D explain how experimental results relate to larger concepts or theories; 6.E predict the causes or effects of a change in, or disruption to, a biological system. 20-26% of multiple choice; scored in FRQs 1, 2, 3, 4, and 6.