# AP Environmental Science exam guide > Cover all nine AP Environmental Science units with published exam weightings, from ecosystems through global change. - Canonical page: https://www.arcadesacademy.com/exams/ap-environmental-science - Markdown source: https://www.arcadesacademy.com/exams/ap-environmental-science/llms.txt - Exam family: AP exams - Governing body: College Board - Official exam information: https://apstudents.collegeboard.org/courses/ap-environmental-science - Who takes it: High school students taking AP Environmental Science for college credit or placement, often alongside or after a first biology or chemistry course. - Follows the fall 2026 course and exam description, from 13 May 2027 - Guide structure last checked against official sources: August 30, 2026 ## Overview AP Environmental Science is an interdisciplinary course that draws on biology, earth science, chemistry, and geography to examine how natural systems work and how human activity changes them. The Course and Exam Description organizes the content into nine units, each with a published weighting range, and pairs it with science practices that include experimental design, quantitative analysis, and evaluating proposed solutions. The exam is unusual among AP sciences in how much arithmetic it expects without leaning on advanced mathematics: dimensional analysis, percentage change, and energy-unit conversions appear throughout, and one free-response question is explicitly calculation-focused. Global change carries the largest published weighting, and the pollution units feed directly into it, so the back half of the course is where the most points sit. Arcade Academy is an independent study workspace. Use the official Course and Exam Description as the authoritative content list, and use the unit pages below to organize review, vocabulary practice, and timed free-response work. ## Exam format - **Total time:** 2 hours 40 minutes - **Section I:** 80 multiple-choice questions in 1 hour 30 minutes, 60% of the exam score - **Section II:** 3 free-response questions in 1 hour 10 minutes, 40% of the exam score - **Free-response types:** One question on designing an investigation, one on analyzing an environmental problem and proposing a solution, and one that does the same with calculations - **Delivery:** Fully digital: both sections are completed in College Board's Bluebook app, with reference information available in the app - **Calculator:** Permitted on the exam - **Score scale:** 1 to 5 ## Scoring The multiple-choice section contributes 60% and the free-response section 40% of a composite score, which College Board converts to the reported 1 to 5 scale using cut points set for that year's exam. Each college decides independently what score earns credit or placement. ## Units AP Environmental Science is organized into 9 units. Each one below lists its published weighting where the governing body publishes one, the topics it covers, and study tips specific to it. ### 1. Unit 1: The Living World: Ecosystems - Position: 1 of 9 - Published weighting: 6–8% - Page: https://www.arcadesacademy.com/exams/ap-environmental-science/unit-1-the-living-world-ecosystems Unit 1 introduces ecosystem structure and the biogeochemical cycles that move matter through it. Terrestrial and aquatic biomes are defined by temperature and precipitation patterns, and energy flow is governed by primary productivity and trophic efficiency. The cycles introduced here reappear in every pollution and global-change topic later in the course. #### Topics - **Terrestrial and aquatic biomes** — How temperature and precipitation define major biomes, and what distinguishes freshwater from marine systems. - **The carbon cycle** — Reservoirs, fluxes, and the human activities that move carbon from long-term storage into the atmosphere. - **The nitrogen and phosphorus cycles** — Fixation, nitrification, and denitrification, and why phosphorus has no significant atmospheric reservoir. - **The hydrologic cycle** — Evaporation, transpiration, precipitation, runoff, and infiltration, and how land use changes each. - **Primary productivity** — Gross and net primary productivity, the units used to express them, and what limits productivity in different systems. - **Trophic levels and food webs** — Energy transfer between levels, the approximate 10% rule, and reading a food web for indirect effects. #### Study tips - Draw each biogeochemical cycle once from memory with reservoirs boxed and fluxes as arrows; the exam tests fluxes more than names. - Practice the 10% rule in both directions, including problems that ask for energy available at a higher trophic level. - Learn biomes by their temperature-and-precipitation signature rather than by a list of species. ### 2. Unit 2: The Living World: Biodiversity - Position: 2 of 9 - Published weighting: 6–8% - Page: https://www.arcadesacademy.com/exams/ap-environmental-science/unit-2-the-living-world-biodiversity Unit 2 asks why biodiversity matters and what maintains it. Ecosystem services, island biogeography, ecological tolerance, and succession give a framework for predicting how a community responds to disturbance. Adaptation ties the unit back to evolutionary reasoning. #### Topics - **Introduction to biodiversity** — Genetic, species, and ecosystem diversity, and the link between diversity and resilience. - **Ecosystem services** — Provisioning, regulating, supporting, and cultural services, with concrete examples of each. - **Island biogeography** — How island size and distance from the mainland shape species richness, and why habitat fragments behave like islands. - **Ecological tolerance** — Ranges of tolerance and optimal ranges, and how a change in conditions shifts species distributions. - **Natural disruptions to ecosystems** — Periodic, episodic, and random disturbances such as fire, storms, and volcanic activity. - **Ecological succession** — Primary and secondary succession, pioneer and keystone species, and the path toward a climax community. #### Study tips - Practice naming a specific ecosystem service for a named ecosystem; generic answers score poorly on free-response questions. - Contrast primary and secondary succession using one worked example each, including what starts the sequence. - Connect island biogeography to habitat fragmentation now; the exam usually tests it in the applied form. ### 3. Unit 3: Populations - Position: 3 of 9 - Published weighting: 10–15% - Page: https://www.arcadesacademy.com/exams/ap-environmental-science/unit-3-populations Unit 3 covers population dynamics for organisms generally and humans specifically. Life-history strategies, survivorship curves, carrying capacity, and growth models set up the quantitative work, and the human section adds age structure diagrams, total fertility rate, and the demographic transition. Growth-rate calculations from this unit appear regularly on the exam. #### Topics - **Generalist and specialist species** — Niche breadth and why specialists are more vulnerable to environmental change. - **K-selected and r-selected species** — Reproductive strategies, parental investment, and the survivorship curve each pattern produces. - **Carrying capacity and population growth** — Exponential versus logistic growth, overshoot, dieback, and the factors that set carrying capacity. - **Age structure diagrams** — Reading a population pyramid for growth, stability, or decline, and connecting shape to future demand. - **Total fertility rate and human population dynamics** — Replacement-level fertility, the drivers that lower fertility rate, and their effect on growth. - **Demographic transition** — The stages of the model and the birth-rate and death-rate pattern that defines each one. #### Study tips - Practice population growth-rate and doubling-time calculations with units written out on every line. - Sketch the three survivorship curves and attach an organism to each so recall is concrete. - Rehearse describing an age structure diagram in one sentence that names the shape and the implication. ### 4. Unit 4: Earth Systems and Resources - Position: 4 of 9 - Published weighting: 10–15% - Page: https://www.arcadesacademy.com/exams/ap-environmental-science/unit-4-earth-systems-and-resources Unit 4 supplies the physical-science background the rest of the course assumes: plate tectonics, soil formation and properties, atmospheric structure, global circulation, watersheds, and the drivers of seasons and regional climate. El Nino and La Nina appear as a case study in coupled ocean and atmosphere behavior. #### Topics - **Plate tectonics** — Plate boundary types and the landforms, earthquakes, and volcanism associated with each. - **Soil formation, erosion, and properties** — Horizons, texture and the soil triangle, permeability and porosity, and the causes of soil loss. - **Earth's atmosphere** — Atmospheric layers, composition, and how temperature changes with altitude in each layer. - **Global wind patterns** — Convection cells, the Coriolis effect, and why deserts and rainforests sit at predictable latitudes. - **Watersheds** — Drainage basin structure and the land-use factors that change runoff quantity and quality. - **Solar radiation, seasons, and climate** — Axial tilt and insolation, plus how latitude, elevation, and proximity to water shape regional climate. #### Study tips - Practice reading the soil texture triangle until it is a fast lookup rather than a puzzle. - Explain global wind patterns starting from unequal heating; the derivation is more durable than a memorized map. - Compare El Nino and La Nina in a two-column table by wind direction, upwelling, and regional effects. ### 5. Unit 5: Land and Water Use - Position: 5 of 9 - Published weighting: 10–15% - Page: https://www.arcadesacademy.com/exams/ap-environmental-science/unit-5-land-and-water-use Unit 5 is the largest applied unit, covering agriculture, forestry, fishing, mining, and urbanization along with the sustainable alternatives to each. The tragedy of the commons frames the whole unit. Free-response questions here frequently ask you to name a practice, explain a consequence, and propose a specific solution. #### Topics - **Tragedy of the commons** — Why shared, unregulated resources are overused, and the policy responses that address it. - **Agricultural practices and the Green Revolution** — Mechanization, high-yield varieties, fertilizer and pesticide use, and their environmental trade-offs. - **Irrigation and pest control methods** — Drip, flood, furrow, and spray irrigation, salinization and waterlogging, and integrated pest management. - **Forestry, fishing, and mining impacts** — Clearcutting, overfishing and bycatch, surface and subsurface mining, and their ecological consequences. - **Urbanization and ecological footprints** — Impervious surfaces, urban runoff and heat islands, urban sprawl, and how footprints are estimated. - **Sustainability practices** — Sustainable agriculture, aquaculture, and forestry, plus green roofs and permeable pavement for runoff. #### Study tips - For every problem in this unit, memorize one specific, named solution; free-response rubrics reward specificity. - Build a practice-to-consequence table for agriculture so cause and effect are linked rather than listed. - Practice explaining a trade-off in both directions, since many questions ask for a drawback of a beneficial practice. ### 6. Unit 6: Energy Resources and Consumption - Position: 6 of 9 - Published weighting: 10–15% - Page: https://www.arcadesacademy.com/exams/ap-environmental-science/unit-6-energy-resources-and-consumption Unit 6 surveys energy sources from fossil fuels through nuclear and the renewables, comparing them on availability, cost, emissions, and land or water impact. Global consumption patterns and the uneven distribution of resources frame the comparison. Energy-unit calculations are common on the calculation free-response question. #### Topics - **Renewable and nonrenewable resources** — How resources are classified, and what distinguishes a renewable source from a sustainable practice. - **Global energy consumption and distribution** — Consumption patterns across countries and the geographic unevenness of energy resources. - **Fossil fuels** — Coal, oil, and natural gas formation, extraction methods, and their comparative emissions profiles. - **Nuclear power** — Fission, reactor components, the waste problem, and the trade-off between low emissions and accident risk. - **Solar, wind, hydro, and geothermal energy** — How each converts a natural flow into electricity, and the siting and intermittency constraints on each. - **Biomass, hydrogen fuel cells, and conservation** — Biomass and biofuel trade-offs, fuel cell chemistry, and the efficiency measures that reduce demand. #### Study tips - Practice energy conversions between kilowatt-hours, joules, and barrels with the units written on every step. - Keep one advantage and one disadvantage per energy source on a single card set for fast comparison questions. - Rehearse a full calculation free-response answer, including showing the setup, since setup earns points even if arithmetic slips. ### 7. Unit 7: Atmospheric Pollution - Position: 7 of 9 - Published weighting: 7–10% - Page: https://www.arcadesacademy.com/exams/ap-environmental-science/unit-7-atmospheric-pollution Unit 7 covers the sources, chemistry, and control of air pollutants. Photochemical smog, thermal inversions, particulates, indoor air pollutants, and acid deposition are the recurring topics, along with the technologies and regulations used to reduce them. Noise pollution appears here as well. #### Topics - **Introduction to air pollution** — Primary and secondary pollutants, their major sources, and the criteria pollutants that are regulated. - **Photochemical smog** — How nitrogen oxides and volatile organic compounds react in sunlight to form ground-level ozone. - **Thermal inversion** — The temperature profile that traps pollutants near the surface and the geography that favors it. - **Particulates and indoor air pollutants** — Sources and health effects of particulate matter, plus radon, asbestos, carbon monoxide, and combustion smoke. - **Acid deposition** — Sulfur and nitrogen oxide sources, downwind effects on soil and water, and buffering capacity. - **Reducing air pollutants** — Scrubbers, catalytic converters, electrostatic precipitators, and the regulations that require them. #### Study tips - Trace each pollutant from source through chemistry to effect to control technology as one linked chain. - Distinguish stratospheric ozone from ground-level ozone explicitly; conflating them is a frequent error. - Attach a specific control technology to each pollutant so solution questions have a concrete answer. ### 8. Unit 8: Aquatic and Terrestrial Pollution - Position: 8 of 9 - Published weighting: 7–10% - Page: https://www.arcadesacademy.com/exams/ap-environmental-science/unit-8-aquatic-and-terrestrial-pollution Unit 8 covers pollution of water and land: point and nonpoint sources, eutrophication, thermal pollution, persistent organic pollutants, solid waste, and sewage treatment. It also introduces the toxicology vocabulary the exam uses, including dose-response curves and the median lethal dose. Bioaccumulation and biomagnification are among the most reliably tested ideas. #### Topics - **Sources of pollution** — Point and nonpoint sources, and the range of human activities that introduce contaminants. - **Eutrophication and thermal pollution** — Nutrient loading, algal blooms, oxygen depletion, and the effect of warm discharge on dissolved oxygen. - **Persistent organic pollutants** — Why some compounds resist breakdown, and how persistence and fat solubility drive their spread. - **Bioaccumulation and biomagnification** — Accumulation within one organism versus concentration increases up trophic levels, with worked examples. - **Solid waste and sewage treatment** — Landfill design, incineration, waste reduction strategies, and the stages of wastewater treatment. - **Dose-response and human health** — Reading a dose-response curve, interpreting the median lethal dose, and linking pathogens to disease. #### Study tips - Work at least one numeric biomagnification problem; the concept is easy but the calculation trips people up. - Sequence the stages of wastewater treatment in order and note what each removes. - Learn eutrophication as a causal chain ending in low dissolved oxygen so you can write it under time pressure. ### 9. Unit 9: Global Change - Position: 9 of 9 - Published weighting: 15–20% - Page: https://www.arcadesacademy.com/exams/ap-environmental-science/unit-9-global-change Unit 9 carries the largest published weighting in the course. It covers stratospheric ozone depletion, the greenhouse effect and climate change, ocean warming and acidification, invasive species, and human impacts on biodiversity. Almost every earlier unit feeds into it, which is why it is worth reviewing last and most thoroughly. #### Topics - **Stratospheric ozone depletion** — How chlorofluorocarbons destroy ozone, the resulting effects, and the treaty response that reduced them. - **The greenhouse effect and greenhouse gases** — How the effect works, the major gases, and their differing residence times and warming potentials. - **Global climate change** — Observed changes, feedback loops such as albedo and permafrost, and the consequences for ecosystems. - **Ocean warming and acidification** — Coral bleaching, thermal expansion and sea level, and the carbonate chemistry behind acidification. - **Invasive species** — Why introduced species can spread rapidly, the damage they cause, and the control options available. - **Human impacts on biodiversity** — Habitat loss, overharvesting, pollution, and the conservation strategies used to slow species decline. #### Study tips - Keep ozone depletion and the greenhouse effect strictly separate in your notes; mixing them is the most common exam error in this unit. - Practice explaining one feedback loop in full, naming the trigger, the amplifying step, and the result. - Review this unit last and most often; it carries the largest published weighting of the nine. ## Study strategies - Weight review by the published percentages, giving global change and the four mid-course units at 10 to 15% the largest share of sessions. - Drill dimensional analysis regularly, because the calculation free-response question and many multiple-choice items hinge on unit conversion rather than difficult mathematics. - Build a specific-example bank: one named law, technology, or case study per major topic, since free-response rubrics reward specificity over general statements. - Practice the three free-response formats separately, especially the design-an-investigation prompt, which requires naming a hypothesis, a control, and an independent and dependent variable. - Use spaced repetition for the heavy vocabulary load, then shift later sessions toward applying terms in written explanations. - Take at least one full timed exam to calibrate pace; 80 multiple-choice questions in 90 minutes leaves little room to linger. ## Frequently asked questions ### How is the AP Environmental Science Exam structured? The exam runs 2 hours 40 minutes. Section I is 80 multiple-choice questions in 1 hour 30 minutes for 60% of the score, and Section II is 3 free-response questions in 1 hour 10 minutes for the remaining 40%. ### Which APES units do students find most challenging? College Board does not rank difficulty. Students most often report trouble with the calculation-heavy portions of the energy and populations units and with keeping ozone depletion separate from the greenhouse effect in Unit 9. Your practice results should drive your plan more than any general list. ### How is the exam scored? The multiple-choice section contributes 60% and the free-response section 40% to a composite score, which is converted to the reported 1 to 5 scale using cut points set each year. Credit and placement decisions are made by individual colleges. ### When do students typically begin exam review? Most commonly, students review each unit as the class completes it, then start cumulative practice and timed free-response work about two months before the May exam. Because the course is vocabulary-dense, early spaced repetition tends to help more than late cramming. ### Is a calculator allowed, and is the exam digital? Calculators are permitted. AP Environmental Science is a fully digital exam taken in College Board's Bluebook app, with reference information available in the app. Confirm current policy on the official exam page before test day. ### Is Arcade Academy affiliated with College Board? No. AP® is a registered trademark of College Board, which was not involved in the production of, and does not endorse, this site. Arcade Academy is an independent educational resource. ## Related exam guides - [AP Biology](https://www.arcadesacademy.com/exams/ap-biology): Study all eight AP Biology units against the College Board framework, from the chemistry of life through ecology. - [AP Chemistry](https://www.arcadesacademy.com/exams/ap-chemistry): Work through all nine AP Chemistry units with published exam weightings, from atomic structure to electrochemistry. - [AP Statistics](https://www.arcadesacademy.com/exams/ap-statistics): The revised five-unit AP Statistics framework, from exploring data and collecting it through inference and regression. ## Independence and trademark notice AP® is a registered trademark of College Board, which was not involved in the production of, and does not endorse, this site. Arcade Academy is an independent educational resource. Confirm current exam format, dates, and policies with College Board directly. AP® is a registered trademark of College Board, which was not involved in the production of, and does not endorse, this site. Arcade Academy is an independent educational resource.