The AP Biology Syllabus covers the major biological concepts and scientific skills required for the Advanced Placement Biology course. The current course framework is organized into eight units, beginning with the chemistry of life and progressing through cells, cellular energetics, heredity, gene expression, evolution and ecology. College Board describes AP Biology as an introductory college-level biology course built around inquiry, experimentation, data analysis and biological reasoning. AP Central
This page provides the AP Biology course content in a structured unit-by-unit format. Each unit contains the individual topics students study during the course, including water and biological macromolecules, cell structure and transport, enzymes, photosynthesis, cellular respiration, cell communication, meiosis, genetics, DNA replication, gene expression, natural selection, population genetics and ecosystem interactions.
The syllabus outline can be used by students to organize their AP Biology notes, identify topics for revision and move directly to detailed study resources for individual lessons. The current College Board Course and Exam Description, effective from fall 2025, retains the eight-unit structure and provides the required course content for each topic.
Unit 1: Chemistry of Life
- Structure of Water and Hydrogen Bonding
Covers the polarity of water, hydrogen bonding and properties such as high specific heat, evaporative cooling, cohesion, adhesion and surface tension that make water important for life. - Elements of Life
Examines the major elements required to build biological molecules, particularly carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur. - Introduction to Macromolecules
Introduces the chemical reactions used to build and break biological macromolecules, including dehydration synthesis, hydrolysis and polymer formation. - Carbohydrates
Covers the structure and function of carbohydrates, including monosaccharides and the formation of linear or branched polysaccharides. - Lipids
Examines the structure and properties of lipids, including hydrophobicity and the differences between saturated and unsaturated fatty acids. - Nucleic Acids (Related)
Covers DNA and RNA as nucleotide polymers, including their sugar, phosphate and nitrogenous-base components and the directional organization of nucleic acid strands. - Proteins
Examines amino acids, peptide bonds and how amino acid sequence and R-group interactions determine protein structure and function.
Unit 2: Cells
- Cell Structure and Function
Examines how cellular structures and organelles, including ribosomes and components of the endomembrane system, perform specialized functions within cells. - Cell Size
Covers how surface area-to-volume ratio affects the exchange of nutrients, wastes, heat and other materials and places limits on cell size and shape. - Plasma Membrane
Examines phospholipids, membrane proteins and other membrane components and how their arrangement helps maintain the internal environment of the cell. - Membrane Permeability
Covers selective permeability and how membrane structure determines which nonpolar, polar and charged substances can cross the plasma membrane. - Membrane Transport
Examines concentration gradients, passive and active transport and the movement of large materials through endocytosis and exocytosis. - Facilitated Diffusion
Explains how channel and transport proteins allow ions and large polar molecules to move down concentration gradients without direct energy input. - Tonicity and Osmoregulation
Covers hypotonic, hypertonic and isotonic conditions, osmosis, water potential and mechanisms organisms use to maintain water and solute balance. - Mechanisms of Transport
Examines energy-dependent membrane transport, including the role of ATP, membrane proteins and ion pumps in establishing electrochemical gradients. - Cell Compartmentalization
Explains how internal membranes and membrane-bound organelles separate cellular processes, reduce competing reactions and provide additional surfaces for biochemical reactions. - Origins of Cell Compartmentalization (Related)
Compares prokaryotic and eukaryotic compartmentalization and examines the endosymbiotic origin of mitochondria and chloroplasts.
Unit 3: Cellular Energetics
- Enzymes
Covers enzymes as biological catalysts, their role in lowering activation energy and the importance of active-site compatibility with substrates. - Environmental Impacts on Enzyme Function
Examines how temperature, pH, chemical conditions and substrate availability can alter enzyme structure, efficiency and reaction rates. - Cellular Energy (Related)
Explores how living systems obtain, transfer and use energy, including energy coupling and the controlled transfer of energy through metabolic pathways. - Photosynthesis
Covers how photosynthetic organisms capture light energy and convert it into chemical energy, including reactions associated with chloroplast structures and carbohydrate production. - Cellular Respiration
Examines how cells extract energy from biological molecules to produce ATP through respiration, electron transport, electrochemical gradients and related metabolic processes.
Unit 4: Cell Communication and Cell Cycle
- Cell Communication
Covers direct and chemical communication between cells and explains how signals can act over short or long distances. - Introduction to Signal Transduction
Introduces receptors, ligands and intracellular signaling components that connect signal reception with a cellular response. - Signal Transduction Pathways
Examines how signaling pathways can alter gene expression, cellular activity or apoptosis and how mutations or chemicals can modify these pathways. - Feedback
Covers negative feedback used to maintain homeostasis and positive feedback that amplifies a biological response. - Cell Cycle
Examines the sequence of the eukaryotic cell cycle, including G1, S and G2 phases, mitosis, cytokinesis and the nondividing G0 state. - Regulation of Cell Cycle
Covers cell-cycle checkpoints, cyclins and cyclin-dependent kinases and examines how loss of normal regulation can contribute to cancer or apoptosis.
Unit 5: Heredity
- Meiosis
Covers the stages of meiosis and explains how diploid cells produce haploid gametes while transmitting chromosomes between generations. - Meiosis and Genetic Diversity (Related)
Examines how crossing over, chromosome assortment and fertilization generate genetic variation and how nondisjunction can produce abnormal chromosome numbers. - Mendelian Genetics
Covers segregation, independent assortment, dominance, probability and genetic crosses used to predict the inheritance of traits. - Non-Mendelian Genetics
Examines inheritance patterns that differ from simple Mendelian ratios, including genetic linkage, codominance and incomplete dominance. - Environmental Effects on Phenotype
Explains how environmental conditions can alter gene expression and cause the same genotype to produce different phenotypes.
Unit 6: Gene Expression and Regulation
- DNA and RNA Structure
Examines DNA and RNA as hereditary molecules, chromosome organization, plasmids and complementary nucleotide base pairing. - DNA Replication
Covers semiconservative DNA replication and the roles of enzymes such as helicase, DNA polymerase, topoisomerase and ligase in copying genetic information. - Transcription and RNA Processing
Examines the transfer of genetic information from DNA to RNA, the functions of mRNA, tRNA and rRNA and the processing of RNA before translation. - Translation
Covers how ribosomes read mRNA codons and use tRNA to assemble amino acids during initiation, elongation and termination of protein synthesis. - Regulation of Gene Expression
Examines regulatory DNA sequences, regulatory proteins and epigenetic modifications that control when and how strongly genes are expressed. - Gene Expression and Cell Specialization
Explains how transcription factors, promoters, enhancers and regulatory molecules produce different patterns of gene expression and specialized cell functions. - Mutations
Covers point, frameshift, nonsense and silent mutations and examines how DNA changes can alter proteins, phenotypes and genetic variation. - Biotechnology (Related)
Introduces techniques used to analyze and manipulate genetic material, including PCR, gel electrophoresis, bacterial transformation and DNA sequencing.
Unit 7: Natural Selection
- Introduction to Natural Selection
Introduces natural selection as a mechanism of evolution and explains how competition, heritable variation and reproductive success influence populations. - Natural Selection
Examines how environmental selective pressures act on phenotypic variation and change the reproductive fitness of organisms. - Artificial Selection
Explains how human selection of particular traits changes genetic and phenotypic variation within domesticated populations. - Population Genetics
Covers changes in allele frequencies caused by mutation, genetic drift, bottleneck events, founder effects and gene flow. - Hardy–Weinberg Equilibrium
Examines the Hardy–Weinberg model, its assumptions and the use of allele and genotype frequencies to evaluate whether a population is evolving. - Evidence of Evolution
Covers geological, geographical, morphological, genetic and molecular evidence used to support evolutionary change and common ancestry. - Common Ancestry
Examines shared cellular and molecular characteristics of eukaryotes, including membrane-bound organelles, linear chromosomes and genes containing introns. - Continuing Evolution
Explains how evolution continues in living populations, including genomic change, drug and pesticide resistance and the emergence of new pathogen variants. - Phylogeny
Covers the use of phylogenetic trees and cladograms to infer evolutionary relationships from morphological, fossil and molecular evidence. - Speciation
Examines reproductive isolation and the formation of new species, together with gradualism, punctuated equilibrium, divergent evolution and convergent evolution. - Variations in Populations
Explains how genetic diversity influences a population’s ability to respond to environmental pressures and affects its risk of decline or extinction. - Origins of Life on Earth
Examines scientific evidence used to construct models for the origin of life, including geological evidence, early Earth conditions and the RNA world hypothesis.
Unit 8: Ecology
- Responses to the Environment (Related)
Examines behavioral and physiological responses to internal and external environmental changes and how organisms exchange information in response to environmental cues. - Energy Flow Through Ecosystems
Covers how organisms acquire and use energy, how energy moves through trophic levels and how matter cycles through ecosystems in major biogeochemical cycles. - Population Ecology
Examines population growth and the effects of birth rate, death rate, population size and environmental conditions on population dynamics. - Effect of Density on Populations
Covers carrying capacity and how resource availability, density-dependent factors and density-independent factors regulate population growth. - Community Ecology
Examines community structure, species composition, species diversity and interactions among populations competing for energy and resources. - Biodiversity
Explains how biodiversity contributes to ecosystem resilience and examines the importance of producers, keystone species and other biotic and abiotic components. - Disruptions in Ecosystems
Examines how environmental change, genetic variation, invasive species and other disturbances can alter populations and ecosystem dynamics.
Disclaimer
Disclaimer: The AP Biology Syllabus and related information on this page are provided for educational and reference purposes. Biology Notes Online is an independent educational website and is not affiliated with, sponsored by, or endorsed by College Board or the Advanced Placement Program. Topic names and course information have been organized for easier study and are accompanied by independently written educational content. Students and teachers should refer to the official College Board resources for the latest AP Biology curriculum, examination requirements and course updates. For copyright concerns or content-related enquiries, contact us at biologynotesonlinecontact@gmail.com.
References
- College Board. (2025). AP Biology Course and Exam Description: Effective Fall 2025.
https://apcentral.collegeboard.org/media/pdf/ap-biology-course-and-exam-description.pdf
The official course framework containing the required AP Biology units, topics, learning objectives, essential knowledge and science practices. AP Central - College Board. (n.d.). AP Biology Course – AP Central.
https://apcentral.collegeboard.org/courses/ap-biology
Official AP Biology course page containing the current Course and Exam Description, course overview and teaching resources. AP Central - College Board. (n.d.). AP Biology – AP Students.
https://apstudents.collegeboard.org/courses/ap-biology
Provides the official student-facing overview of the eight AP Biology units, course skills and exam weighting for each unit. AP Students - College Board. (n.d.). AP Biology Exam – AP Central.
https://apcentral.collegeboard.org/courses/ap-biology/exam
Provides the current AP Biology examination structure, question types, timing and scoring distribution. AP Central - College Board. (n.d.). AP Biology Exam – AP Students.
https://apstudents.collegeboard.org/courses/ap-biology/assessment
Student reference for the AP Biology examination format, multiple-choice and free-response sections, exam resources and preparation information.