Exam Overview
Format, big ideas, and the formula sheet.
The AP Biology exam is 3 hours: half multiple-choice, half free-response. Every question is anchored in one of four Big Ideas and tests one of six Science Practices. A four-function calculator and a formula sheet are provided.
Section structure
| Section | Questions | Time | Weight |
|---|---|---|---|
| I — Multiple choice | 60 | 90 min | 50% |
| II — Long FRQ ×2 | 2 (8–10 pts each) | ~50 min | ~33% |
| II — Short FRQ ×4 | 4 (4 pts each) | ~40 min | ~17% |
The Four Big Ideas
| Code | Idea | Plain meaning |
|---|---|---|
| EVO | Evolution | Evolution drives the diversity and unity of life. |
| ENE | Energetics | Cells use energy and matter to grow, reproduce, and stay in homeostasis. |
| IST | Information Storage & Transmission | Living systems store, retrieve, and transmit information. |
| SYI | Systems Interactions | Biological systems interact and produce emergent properties. |
The Six Science Practices
- Concept Explanation — Explain biological concepts, processes, and models.
- Visual Representations — Analyze diagrams, models, and figures.
- Questions and Methods — Identify scientific questions and design methods.
- Representing and Describing Data — Tables, graphs, descriptions.
- Statistical Tests and Data Analysis — chi-square, error bars, calculations.
- Argumentation — Justify claims with evidence.
Practices 5 and 6 dominate the FRQ rubrics — strong calculation and argumentation are non-negotiable.
Unit weights at a glance
| Unit | Title | Big Idea(s) | Weight |
|---|---|---|---|
| 1 | Chemistry of Life | Energetics, Systems | 8–11% |
| 2 | Cell Structure and Function | Energetics, Systems | 10–13% |
| 3 | Cellular Energetics | Energetics | 12–16% |
| 4 | Cell Communication & Cell Cycle | Information, Systems | 10–15% |
| 5 | Heredity | Information | 8–11% |
| 6 | Gene Expression & Regulation | Information | 12–16% |
| 7 | Natural Selection | Evolution | 13–20% |
| 8 | Ecology | Systems | 10–15% |
Formula sheet (memorize cold)
The College Board provides the sheet, but you should still know how to apply each one without thinking.
Water potential
Ψ = Ψp + Ψs
Ψs = −iCRT
i = ionization constant (1.0 sucrose, 2.0 NaCl) ·
C = molarity (mol/L) ·
R = 0.0831 L·bar/(mol·K) ·
T = Kelvin (°C + 273)
Hardy-Weinberg
p + q = 1
p² + 2pq + q² = 1
p² = AA · 2pq = Aa · q² = aa.
Conditions: no mutation, random mating, no gene flow, no drift, no selection.
Chi-square
χ² = Σ (O − E)² / E
Compare to critical value at df = (categories − 1), p = 0.05. Accept H₀ if χ² < critical.
Statistics
x̄ = Σxᵢ / n
s = √[ Σ(xᵢ − x̄)² / (n − 1) ]
SEx̄ = s / √n
Mean · standard deviation · standard error of the mean.
Probability
P(A or B) = P(A) + P(B)
P(A and B) = P(A) × P(B)
Mutually exclusive (or-rule) · independent (and-rule).
Population growth
dN/dt = rN (exponential)
dN/dt = rN[(K − N)/K] (logistic)
K = carrying capacity. r-selected fast in J-curve; K-selected stabilizes at S-curve.
Misc.
pH = −log[H⁺]
C₁V₁ = C₂V₂
Q₁₀ = (k₂/k₁)^(10/(T₂−T₁))
pH · dilution · temperature coefficient.