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AP Biology is organized into 8 units by the College Board Course and Exam Description (CED), running from the chemistry of life up to whole-ecosystem ecology. Each unit is genuinely different biology with its own vocabulary, mechanisms, and exam traps. This hub explains the structure, the May exam format, and links to a dedicated study page for every unit.
Built for US students. Live online coaching in your time zone (ET / CT / MT / PT), pricing in USD.
The College Board defines AP Biology through its Course and Exam Description. The 8 units are sequenced from the smallest scale to the largest: you start with the atoms and molecules of life (Unit 1), build up to the cell (Unit 2), learn how cells harvest and spend energy (Unit 3), how they communicate and divide (Unit 4), then move into inheritance (Unit 5) and the molecular machinery behind it (Unit 6), and finally zoom out to populations evolving (Unit 7) and interacting in ecosystems (Unit 8).
Crucially, the units are not equally weighted on the exam. The CED publishes approximate weighting ranges rather than exact percentages, and the heaviest units are Natural Selection, Cellular Energetics, and Gene Expression. The lighter units — Chemistry of Life and Heredity — are still foundational, because later units assume you know them cold.
Across all 8 units, AP Biology threads four big ideas: Evolution; Energetics; Information storage and transmission; and Systems interactions. The exam rewards students who can connect a unit-level fact to one of these big ideas rather than memorizing it in isolation.
60 multiple-choice questions in 90 minutes. Worth 50% of the score. Many questions are data- and graph-based, asking you to interpret an experiment rather than recall a definition.
6 free-response questions in 90 minutes — 2 long FRQs and 4 short FRQs. Worth 50% of the score. Long FRQs include experimental design and data analysis; short FRQs test a focused concept or model.
The exam is administered in May and scored on the 1 to 5 AP scale, where a 3 is typically considered passing and a 5 is the top score. Most colleges award credit for a 4 or 5.
Each page covers the unit's key topics and learning objectives, the pitfalls students fall into, how it is tested in MCQ and FRQ form, and how we coach it.
8–11% (approximate, per the CED)
Water, macromolecules, and the chemistry that makes biology run — properties of water, the four macromolecule classes, and how structure dictates function.
10–13% (approximate, per the CED)
Organelles, membranes, transport, and how surface-area-to-volume ratio constrains cell size. The structural foundation everything else builds on.
12–16% (approximate, per the CED)
Enzymes, photosynthesis, and cellular respiration — the energy-flow mechanisms that AP Biology tests more heavily than almost anything else.
10–15% (approximate, per the CED)
Signal transduction, feedback, and the regulated cell cycle including mitosis and its checkpoints — how cells talk and how that goes wrong in cancer.
8–11% (approximate, per the CED)
Meiosis, Mendelian and non-Mendelian inheritance, linkage, and the chromosomal basis of genetic variation. Heavy on probability and pedigrees.
12–16% (approximate, per the CED)
DNA replication, transcription, translation, gene regulation, mutations, and biotechnology — the molecular flow of information and how it is controlled.
13–20% (approximate, per the CED)
Evidence for evolution, natural selection, Hardy-Weinberg equilibrium, speciation, and phylogenetics. The highest-weight unit, and the most quantitative.
10–15% (approximate, per the CED)
Energy flow, population dynamics, community interactions, ecosystems, and responses to disruption. Connects every prior unit at the scale of populations and biospheres.
We teach all 8 units live online, weight the time toward the high-yield ones, and grade your FRQs against the real rubric. Faculty trained at AIIMS (All India Institute of Medical Sciences, India's top medical school).
WhatsApp is free from the US — no international call needed. Live online classes in your US time zone (ET/CT/MT/PT).