College Board · Two-semester introductory college biology

AP Biology Simulations and Calculators by Unit

Free AP Biology simulations and calculators for all eight units, from macromolecules and cells to heredity, gene expression, evolution and ecology.

19 tools across 8 units

Unit 1: Chemistry of Life

Water and hydrogen bonding, the elements of life, and the structure and function of carbohydrates, lipids, nucleic acids and proteins.

Biology DNA Double Helix Explorer The grooves, and the strand offset that creates them.
Biology Amino Acid 3D Explorer All 20 amino acids in 3D, grouped by side chain, their charges changing as you move the pH.
Biology Reverse Complement Calculator Reverse complement, complement or reverse of DNA or RNA, with IUPAC codes, length and GC content.

Unit 2: Cells

Organelles and what they do, cell size, the plasma membrane, membrane permeability and transport, tonicity and osmoregulation, and compartmentalisation.

Unit 3: Cellular Energetics

How enzymes work and what changes their activity, including inhibitors, how cells capture and use energy, photosynthesis and cellular respiration.

Unit 4: Cell Communication and Cell Cycle

How cells signal to each other, signal transduction pathways, positive and negative feedback, and the cell cycle and its regulation.

Biology Mitosis and Meiosis Explorer Mitosis and meiosis stage by stage, with chromosome and chromatid counts for your 2n.

Unit 5: Heredity

Meiosis and genetic diversity, Mendelian genetics and chi-square tests, codominance, sex-linked and other non-Mendelian inheritance, and environmental effects on phenotype.

Unit 6: Gene Expression and Regulation

DNA and RNA structure, DNA replication, transcription and RNA processing, translation, gene regulation, mutations, and biotechnology such as PCR and gel electrophoresis.

Unit 7: Natural Selection

Natural and artificial selection, population genetics and Hardy-Weinberg equilibrium, evidence for evolution and common ancestry, phylogeny, speciation and the origins of life.

Biology Hardy-Weinberg Calculator Allele and genotype frequencies from one known value or from counts, with a chi-square test of equilibrium.

Unit 8: Ecology

Responses to the environment, energy flow through ecosystems, population growth and density, interactions within communities, biodiversity and disruptions to ecosystems.

What are the units in AP Biology?

The College Board course framework divides AP Biology into eight units: Chemistry of Life; Cells; Cellular Energetics; Cell Communication and Cell Cycle; Heredity; Gene Expression and Regulation; Natural Selection; and Ecology. On this page, each unit has a short summary and the tools on this site that teach it.

Unit 7 carries the most weight on the exam, 13 to 20 percent of the multiple-choice section, and its population genetics is where the Hardy-Weinberg calculator belongs. The equations and formulas sheet in the course description includes chi-square, Hardy-Weinberg, water potential and Simpson’s diversity index, and each has a calculator listed under its unit.

Course outline: College Board, AP Biology Course and Exam Description, effective fall 2025.