An interdisciplinary look at the science behind environmental problems and their solutions.
Study guide last reviewed September 25, 2026 · see what changed
Format reflects the current published structure — always confirm against AP Central before test day, since formats occasionally change.
| Section | Details | Time | Weight |
|---|---|---|---|
| Section I – Multiple Choice | 80 questions | 1 hr 30 min | 60% |
| Section II – Free Response | 3 questions (design/analysis, data analysis, document-based) | 1 hr 10 min | 40% |
Straight answers about the AP Environmental Science exam — format, credit, dates, and this site.
Section I – Multiple Choice: 80 questions (1 hr 30 min, 60% of the total score); Section II – Free Response: 3 questions (design/analysis, data analysis, document-based) (1 hr 10 min, 40% of the total score). See the Exam Format tab above for the full breakdown, and always double-check the current year's format on AP Central before test day.
It's multiple-choice questions and written free-response or essay questions.
It depends entirely on the college — most award credit for a 3 or higher, but many selective schools require a 4 or a 5, and some don't grant credit at all for certain scores. Always check your target college's own AP credit policy page rather than assuming a 3 will count everywhere.
AP exams are administered during the College Board's annual testing window in the first two full weeks of May, with the exact date and time for each subject set by the College Board and announced the preceding fall. Check AP Central or your school's AP coordinator for this year's exact date.
Yes. The unit-by-unit study guide, worked examples, practice quiz, and full-length timed practice exam on this page are all free, with no login, signup, or paywall.
Unit-by-unit breakdown of what the course actually covers, in teaching order.
The carbon, nitrogen, phosphorus, and water (hydrologic) cycles traced step by step — for nitrogen specifically: fixation (by bacteria or lightning), nitrification, assimilation, ammonification, and denitrification. Energy flow through trophic levels via food chains and food webs, with the 10% rule limiting energy transfer and explaining why top predators are rare and biomagnification of toxins concentrates at higher trophic levels.
Species richness, evenness, and biodiversity indices as quantitative biodiversity measures, plus the ecosystem services biodiversity provides (pollination, water purification, soil formation, genetic resources for medicine/agriculture). Threats specifically named: habitat fragmentation, invasive species, overharvesting, and the difference between endemic, threatened, and endangered species classifications.
The exponential growth equation and logistic growth model incorporating carrying capacity (K), plus r-selected species (many offspring, little parental care, e.g. insects) versus K-selected species (few offspring, high investment, e.g. elephants). Density-dependent limiting factors (competition, disease, predation) versus density-independent factors (natural disasters, climate) and survivorship curve types (Type I, II, III).
Plate tectonics (divergent, convergent, transform boundaries) and their role in earthquakes, volcanism, and mineral resource formation. Soil composition and horizons (O, A, B, C, R layers), soil formation factors, and how soil texture/composition affects fertility, erosion risk, and water infiltration — directly connecting geology to agricultural viability.
Industrialized/monoculture agriculture versus sustainable practices (crop rotation, contour plowing, no-till farming, integrated pest management), and specific consequences like the Green Revolution's tradeoffs (higher yields vs. fertilizer/pesticide dependency and monoculture vulnerability). Deforestation causes (logging, agriculture, urbanization) and consequences (soil erosion, biodiversity loss, altered water cycles, carbon release).
Nonrenewable resources (coal, oil, natural gas, nuclear fission) versus renewables (solar, wind, hydroelectric, geothermal, biomass), each with specific extraction methods, efficiency figures, and environmental tradeoffs (e.g., fracking's water contamination risk, nuclear's waste storage problem, hydroelectric's habitat disruption). Global energy consumption patterns and the concept of net energy/EROI (energy returned on energy invested).
Primary pollutants (CO, NOx, SOx, particulates) versus secondary pollutants formed by reactions in the atmosphere (like ground-level ozone from photochemical smog). Acid rain's formation from SO2 and NOx reacting with atmospheric water, and its effects on lakes, forests, and buildings. Stratospheric ozone depletion via CFCs releasing chlorine radicals that catalytically destroy ozone, and the Montreal Protocol's role in addressing it.
Point source (identifiable, like a pipe) versus nonpoint source (diffuse, like agricultural runoff) water pollution, eutrophication's full sequence (nutrient runoff, algal bloom, decomposition, oxygen depletion, fish kill), and biological/chemical measures of water quality (BOD, dissolved oxygen, indicator species). Solid waste management hierarchy (reduce, reuse, recycle) and hazardous waste handling, including specific concerns like heavy metal contamination and landfill leachate.
The greenhouse effect mechanism (radiative forcing, specific gases: CO2, methane, water vapor, N2O, and their relative global warming potentials), evidence for climate change (ice core data, temperature records, sea level rise, ocean acidification from CO2 absorption), and projected/observed consequences (extreme weather, ecosystem shifts, glacial retreat). Mitigation strategies (renewable energy transition, carbon capture, reforestation) versus adaptation strategies, and international agreements like the Paris Agreement.
Concrete, fully worked examples — this is what separates a page reviewers see as genuinely useful from one that just lists topics.
Logistic growth: a population of 200 has a carrying capacity of 1000 and growth rate r=0.3/year. Estimate its growth rate right now using dN/dt = rN(1−N/K).
dN/dt = 0.3 × 200 × (1 − 200/1000) = 0.3 × 200 × 0.8 = 48 individuals/year. Growth rate peaks at N = K/2 (here, 500) and slows as the population approaches K — a graph-reading skill tested at least as often as the calculation itself.
EROI comparison: a coal plant returns 30 units of energy for every 1 unit invested extracting it (EROI=30); a biofuel process returns 1.3 units for every 1 invested (EROI=1.3). What does this actually mean?
An EROI of 1.3 means the process barely produces more usable energy than it consumes to run — it can still be net-positive but leaves very little surplus energy for society, while EROI=30 leaves enormous surplus. Comparing EROI values, not just whether a source is renewable, is often the deciding factor examiners want in an energy-policy FRQ.
Ozone depletion mechanism: explain, step by step, how a single CFC molecule can destroy many ozone molecules.
UV light breaks a C−Cl bond in the CFC, releasing a free chlorine radical. That radical reacts with O₃ to form ClO and O₂, then ClO reacts with a free oxygen atom to regenerate the original Cl radical plus another O₂. Because the chlorine radical is regenerated, not consumed, a single atom can catalytically destroy thousands of ozone molecules before it's eventually removed from the stratosphere — that catalytic cycle is the specific mechanism FRQs ask you to trace.
Eutrophication sequence: trace what happens after excess fertilizer runs off into a lake, step by step.
Nutrient runoff (mainly phosphorus/nitrogen) → algal bloom (rapid algae growth) → algae die and sink → decomposer bacteria consume the dead algae, using up dissolved oxygen → oxygen levels crash → fish and other oxygen-dependent organisms die (a fish kill). Each FRQ that asks about eutrophication expects this full causal chain, not just 'too many nutrients caused a fish kill.'
Radiative forcing comparison: methane has a much higher global warming potential (GWP) per molecule than CO₂, but CO₂ still drives more total warming. Why?
GWP measures warming effect per molecule over a set time period, but total atmospheric impact depends on both potency and quantity/concentration. CO₂ is far more abundant in the atmosphere than methane, so its much larger total quantity outweighs methane's higher per-molecule potency — a distinction between potency and total impact that's specifically tested.
The errors that cost the most points across the whole exam, not just one unit.
Unofficial practice questions written for this study guide — not official AP content and not from College Board. Use them to self-check, then use the real past free-response questions below for authentic exam practice.
Unofficial practice, timed to feel like the real thing. Section I pulls from this page's full multiple-choice bank; Section II gives you free-response prompts to write out and self-score against a rubric. Bank size is still growing toward full exam length — timing is paced per-question, not pulled from this subject's official duration.