AP Biology · Science
AP Biology: free lessons and course outline
College-level biology, from the hydrogen bonds in a water molecule to the carbon flowing through an ecosystem, taught unit by unit to the College Board framework. Every lesson ends with practice problems that have full worked answers, and every unit ends with a 20-question quiz that mixes stimulus-based multiple choice with short free-response items scored against the real AP rubric. Exam format from 2027: this is a hybrid digital exam: multiple choice in Bluebook, free response handwritten in a paper booklet. Work the free-response practice on paper first, then either type your answer into the response box or photograph your page and have it read in for scoring.
AP Biology follows the eight units of the College Board course framework. Unit 7 (natural selection) is the heaviest at 13–20%, with Units 3 and 6 close behind at 12–16% each, so the lessons below give those units the most room. The exam is three hours: 60 multiple-choice questions in 90 minutes for the first half, then six free-response questions in 90 minutes for the second, two long questions worth 9 points each (interpreting and evaluating experimental results, and the same task with a graph you construct) and four short questions worth 4 points each (scientific investigation, conceptual analysis, analysis of a model or visual representation, and data analysis). Every unit below ends with a quiz of 15 multiple-choice questions and 5 short free-response questions, several of them built on described data sets, graphs, and models, with a writing space that scores against the four-point AP rubric and a model 4/4 response to compare against.
- U1Chemistry of Life8–11%
- U2Cell Structure and Function10–13%
- U3Cellular Energetics12–16%
- U4Cell Communication and Cell Cycle10–15%
- U5Heredity8–11%
- U6Gene Expression and Regulation12–16%
- U7Natural Selection13–20%
- U8Ecology10–15%
Every lesson, unit by unit
U1 is free to read below. The other units open with a free month or a paid plan.
U1 Chemistry of Life 8–11% of the examFREE
U2 Cell Structure and Function 10–13% of the exam
- 2.1 Cell structure and function
- 2.2 Cell size and surface area to volume
- 2.3 The plasma membrane
- 2.4 Membrane permeability and the cell wall
- 2.5 Membrane transport
- 2.6 Facilitated diffusion
- 2.7 Tonicity and osmoregulation
- 2.8 Mechanisms of transport
- 2.9 Cell compartmentalization
- 2.10 Origins of cell compartmentalization
U3 Cellular Energetics 12–16% of the exam
- 3.1 Enzymes
- 3.2 Environmental effects on enzymes
- 3.3 Cellular energy and ATP
- 3.4 Photosynthesis: the light reactions
- 3.5 Photosynthesis: the Calvin cycle
- 3.6 Cellular respiration: glycolysis and the Krebs cycle
- 3.7 Cellular respiration: ATP synthesis and fermentation
U4 Cell Communication and Cell Cycle 10–15% of the exam
- 4.1 Cell communication
- 4.2 Signal transduction pathways: reception to response
- 4.3 Changes in signaling pathways
- 4.4 Feedback and homeostasis
- 4.5 The cell cycle and interphase
- 4.6 Mitosis and cytokinesis
- 4.7 Regulation of the cell cycle
U5 Heredity 8–11% of the exam
- 5.1 Meiosis
- 5.2 Meiosis and genetic diversity
- 5.3 Mendelian genetics
- 5.4 Pedigrees and sex-linked inheritance
- 5.5 Dominance patterns, pleiotropy, non-nuclear inheritance
- 5.6 Linked genes, gene mapping, and chi-square
- 5.7 Environmental effects on phenotype
U6 Gene Expression and Regulation 12–16% of the exam
- 6.1 DNA and RNA structure
- 6.2 DNA replication
- 6.3 Transcription and RNA processing
- 6.4 Translation and the genetic code
- 6.5 Gene regulation in prokaryotes: operons
- 6.6 Gene regulation in eukaryotes and cell specialization
- 6.7 Mutations
- 6.8 Genetic variation: horizontal gene transfer and selection
- 6.9 Biotechnology
U7 Natural Selection 13–20% of the exam
- 7.1 Introduction to Natural Selection
- 7.2 Natural Selection: Variation and Fitness
- 7.3 Artificial Selection
- 7.4 Population Genetics and Random Events
- 7.5 Hardy-Weinberg Equilibrium
- 7.6 Evidence of Evolution and Common Ancestry
- 7.7 Continuing Evolution and Genetic Diversity
- 7.8 Phylogenetic Trees and Cladograms
- 7.9 Speciation and Extinction
- 7.10 Origins of Life on Earth
U8 Ecology 10–15% of the exam
- 8.1 Responses to the Environment
- 8.2 Energy Flow Through Ecosystems
- 8.3 Biogeochemical Cycles
- 8.4 Population Growth and Density
- 8.5 Community Ecology and Species Interactions
- 8.6 Biodiversity, Keystone Species, and Succession
- 8.7 Disruptions to Ecosystems
Keep going in the full AP Biology course
All of U1 (Chemistry of Life) is free to everyone, with no account. The course has 64 lessons, each with worked examples and practice problems that come with full solutions. A free account can also start a free month of the whole course, with no card.
Open this lesson in the courseSee the whole course