Exam Overview
Format, big ideas, and the math reference sheet.
The AP Environmental Science exam is 2 h 40 min. Section I is 80 multiple-choice in 90 minutes (60% of the score). Section II is 3 free-response questions in 70 minutes (40%). A four-function, scientific, or graphing calculator is allowed throughout.
Section structure
| Section | Questions | Time | Weight |
|---|---|---|---|
| I — Multiple choice | 80 | 90 min | 60% |
| II — Free response | 3 | 70 min | 40% |
The three FRQ types
One of each appears on every exam. Learn the rubric for each.
| FRQ | What it asks |
|---|---|
| Q1 · Design an Investigation | Propose a hypothesis. Identify IV, DV, controlled variables. Describe procedure. Justify a conclusion. |
| Q2 · Analyze Environmental Problem & Propose Solution | Describe the problem. Explain causes and effects. Propose AND defend a specific solution. |
| Q3 · Analyze Problem with Calculations | Same as Q2 plus multi-step quantitative calculations with required dimensional analysis. |
The Four Big Ideas
| Code | Idea | Plain meaning |
|---|---|---|
| ERT | Energy Transfer in Living Systems | Energy flow drives ecosystems and human energy systems. |
| EIN | Interactions Between Earth Systems | Land, water, air, and biota interact and respond to disturbance. |
| STB | Sustainability | Resources are finite; long-term human activity must balance use and renewal. |
| EUR | Environmental & Health Effects | Environmental change affects human and ecosystem health. |
Unit weights at a glance
| Unit | Title | Big Idea(s) | Weight |
|---|---|---|---|
| 1 | The Living World: Ecosystems | Energy Transfer, Earth Interactions | 6–8% |
| 2 | The Living World: Biodiversity | Energy Transfer, Earth Interactions | 6–8% |
| 3 | Populations | Earth Interactions, Sustainability | 10–15% |
| 4 | Earth Systems and Resources | Earth Interactions | 10–15% |
| 5 | Land and Water Use | Sustainability, Health & Environment | 10–15% |
| 6 | Energy Resources and Consumption | Sustainability, Health & Environment | 10–15% |
| 7 | Atmospheric Pollution | Health & Environment | 7–10% |
| 8 | Aquatic and Terrestrial Pollution | Health & Environment | 7–10% |
| 9 | Global Change | Sustainability, Health & Environment | 15–20% |
Math reference (memorize cold)
The College Board provides a sheet, but you should still know how to apply each one without thinking.
Energy unit conversions
1 kWh = 3.6 × 10⁶ J = 3.6 MJ
1 kcal (food Calorie) = 4184 J
1 BTU ≈ 1055 J
E = P × t (kWh = kW × hr)
Watch capitalization: 1 Calorie = 1 kcal = 1000 cal. The W in "Wh" is power; the kWh is energy.
Population growth
r% = (CBR − CDR) / 10
Doubling time = 70 / r%
Population in n doublings = N₀ × 2ⁿ
CBR/CDR are per 1000 per year. Don\'t forget immigration / emigration if given.
Radioactive decay
N = N₀ × (½)^(t/T)
T = half-life. After n half-lives, fraction remaining = (½)ⁿ.
Mass / volume / area
1 metric ton = 1000 kg
1 short ton = 2000 lb
1 lb ≈ 0.454 kg
1 gal = 3.785 L
1 hectare = 10,000 m² ≈ 2.47 acres
When given in tons, always check whether it is metric or short. The two differ by ~10%.
Concentration
ppm = mg/L (in dilute aqueous solution)
ppb = µg/L
1% = 10,000 ppm
Used for water-quality and atmospheric-pollutant problems.
Efficiency
% Efficiency = (useful output / input) × 100
A 30%-efficient power plant produces 30 J of electricity per 100 J of fuel energy; 70 J is lost as waste heat.