AP Environmental Science Notes — Key Concepts by Unit

AP Environmental Science (APES) is a lab-science course that integrates physical, biological, and social sciences. The FRQ always includes a calculation question. These notes organize key facts and concepts by unit with the quantitative formulas you need.

Units 1–2: Earth Systems and Biodiversity

Biogeochemical cycles: carbon cycle (photosynthesis/respiration, fossil fuels), nitrogen cycle (fixation by bacteria, nitrification, denitrification), phosphorus cycle (no atmospheric component). Biomes: determined by temperature and precipitation. Biodiversity hotspots: high endemism + severe habitat loss. Ecosystem services: provisioning, regulating, cultural, supporting. Keystone species have disproportionate ecosystem impact. Island biogeography: larger islands and those closer to mainland have more species.

Units 3–4: Populations and Land/Water Use

Population ecology: exponential growth (J-curve) vs. logistic growth (S-curve); carrying capacity K. Age structure diagrams predict growth: wide base = fast growth. Tragedy of the commons (Hardin). Agriculture: irrigation drawbacks (salinization, aquifer depletion — Ogallala Aquifer). Deforestation consequences: soil erosion, flooding, biodiversity loss. GMO crops: benefits and controversies. Sustainable forestry: selective cutting vs. clear-cutting impacts.

Units 5–6: Energy Resources and Pollution

Fossil fuels: coal (most CO₂), oil, natural gas. EROI = energy return on investment — higher = better. Nuclear: fission (not fusion); waste storage problem; Chernobyl, Fukushima case studies. Renewable: solar (PV and thermal), wind, hydroelectric (disrupts migration, alters sediment), geothermal, biomass. Water pollution: point source (pipe outfall) vs. nonpoint source (agricultural runoff). Eutrophication sequence: nutrient loading → algal bloom → decomposition → hypoxia. Air pollutants: primary (SO₂, NOₓ, CO, particulates) vs. secondary (ozone, smog).

Units 7–9: Climate Change and Policy

Greenhouse gases: CO₂, CH₄ (25× more potent over 100 years), N₂O, water vapor, CFCs (ozone depleter). Climate feedback loops: ice-albedo feedback (positive), carbon cycle feedbacks. Ozone depletion: CFCs → chlorine radicals → catalytic destruction; Montreal Protocol (1987) success. International agreements: Kyoto Protocol, Paris Agreement (1.5°C target). Cap-and-trade vs. carbon tax. Environmental justice: polluting facilities disproportionately in low-income/minority communities.

APES Study Guide · APES Flashcards · How to Get a 5 on APES

AP and Advanced Placement are trademarks of College Board. AimFive is not affiliated with or endorsed by College Board.