AP Environmental Science

What the course covers

9 units, with exam weights

1. Unit 1

   The Living World: Ecosystems

   6-8% of examFree
   Earth as a set of connected living systems. Species interactions and the resources that shape them, the terrestrial and aquatic biomes, the carbon, nitrogen, phosphorus, and hydrologic cycles with their reservoirs and residence times, primary productivity (GPP, NPP, and respiration), trophic levels, the 10% rule and the laws of thermodynamics behind it, and food chains and food webs.
   11 topics

   1. 1.1Introduction to Ecosystems
   2. 1.2Terrestrial Biomes
   3. 1.3Aquatic Biomes
   4. 1.4The Carbon Cycle
   5. 1.5The Nitrogen Cycle
   6. 1.6The Phosphorus Cycle
   7. 1.7The Hydrologic (Water) Cycle
   8. 1.8Primary Productivity
   9. 1.9Trophic Levels
   10. 1.10Energy Flow and the 10% Rule
   11. 1.11Food Chains and Food Webs

2. Unit 2

   The Living World: Biodiversity

   6-8% of exam
   Why diversity matters and how communities change. Genetic, species, and habitat diversity and their link to resilience; the four categories of ecosystem services and what human disruption costs; island biogeography; ecological tolerance; natural disruptions on different time scales; adaptation through natural selection; and primary and secondary succession, with keystone and indicator species.
   7 topics

   1. 2.1Introduction to Biodiversity
   2. 2.2Ecosystem Services
   3. 2.3Island Biogeography
   4. 2.4Ecological Tolerance
   5. 2.5Natural Disruptions to Ecosystems
   6. 2.6Adaptations
   7. 2.7Ecological Succession

3. Unit 3

   Populations

   10-15% of exam
   How populations grow, crash, and change. Generalists and specialists, r-selected and K-selected strategies, survivorship curves, carrying capacity and overshoot, resource limits on growth, and then human populations: age structure diagrams, total fertility rate, birth, death, and migration, density-dependent and density-independent factors, rate of natural increase, the rule of 70, and the demographic transition model.
   9 topics

   1. 3.1Generalist and Specialist Species
   2. 3.2K-Selected r-Selected Species
   3. 3.3Survivorship Curves
   4. 3.4Carrying Capacity
   5. 3.5Population Growth and Resource Availability
   6. 3.6Age Structure Diagrams
   7. 3.7Total Fertility Rate
   8. 3.8Human Population Dynamics
   9. 3.9Demographic Transition

4. Unit 4

   Earth Systems and Resources

   10-15% of exam
   The physical Earth that supports life. Plate boundaries and the earthquakes, volcanoes, and mountains they produce; how soil forms, erodes, and is tested (horizons, texture, porosity, permeability, water-holding capacity, the soil texture triangle); the composition and layers of the atmosphere; global wind patterns; watersheds; solar radiation, latitude, and the seasons; rain shadows; and El Niño and La Niña.
   9 topics

   1. 4.1Plate Tectonics
   2. 4.2Soil Formation and Erosion
   3. 4.3Soil Composition and Properties
   4. 4.4Earth's Atmosphere
   5. 4.5Global Wind Patterns
   6. 4.6Watersheds
   7. 4.7Solar Radiation and Earth's Seasons
   8. 4.8Earth's Geography and Climate
   9. 4.9El Niño and La Niña

5. Unit 5

   Land and Water Use

   10-15% of exam
   How people use land and water, what it costs, and how to do it sustainably. The tragedy of the commons, clearcutting, the Green Revolution and agricultural damage (tilling, slash-and-burn, fertilizers), irrigation methods and their water losses, pest control and resistance, meat production (CAFOs versus pasture and rotational grazing, overgrazing, desertification), overfishing, mining, urbanization and impervious surfaces, ecological footprints, then the fixes: sustainability and sustainable yield, urban runoff reduction, integrated pest management, soil conservation, aquaculture, and sustainable forestry.
   17 topics

   1. 5.1The Tragedy of the Commons
   2. 5.2Clearcutting
   3. 5.3The Green Revolution
   4. 5.4Impact of Agricultural Practices
   5. 5.5Irrigation Methods
   6. 5.6Pest Control Methods
   7. 5.7Meat Production Methods
   8. 5.8Impacts of Overfishing
   9. 5.9Impacts of Mining
   10. 5.10Impacts of Urbanization
   11. 5.11Ecological Footprints
   12. 5.12Introduction to Sustainability
   13. 5.13Methods to Reduce Urban Runoff
   14. 5.14Integrated Pest Management
   15. 5.15Sustainable Agriculture
   16. 5.16Aquaculture
   17. 5.17Sustainable Forestry

6. Unit 6

   Energy Resources and Consumption

   10-15% of exam
   Where energy comes from and what it costs the environment. Renewable versus nonrenewable sources, global consumption trends, fuel types (wood, peat, coal ranks, natural gas, tar sands, cogeneration), where resources occur, fossil fuel power plants and fracking, nuclear fission, half-life, and accidents, biomass and ethanol, solar, hydroelectric and tidal, geothermal, hydrogen fuel cells, wind, and energy conservation at home and at scale.
   13 topics

   1. 6.1Renewable and Nonrenewable Resources
   2. 6.2Global Energy Consumption
   3. 6.3Fuel Types and Uses
   4. 6.4Distribution of Natural Energy Resources
   5. 6.5Fossil Fuels
   6. 6.6Nuclear Power
   7. 6.7Energy from Biomass
   8. 6.8Solar Energy
   9. 6.9Hydroelectric Power
   10. 6.10Geothermal Energy
   11. 6.11Hydrogen Fuel Cell
   12. 6.12Wind Energy
   13. 6.13Energy Conservation

7. Unit 7

   Atmospheric Pollution

   7-10% of exam
   What people put into the air and how to take it out. Sources and effects of the major pollutants ($\mathrm{CO_2}$, $\mathrm{SO_2}$, $\mathrm{NO_x}$, CO, particulates, lead), primary versus secondary pollutants, photochemical smog and its daily cycle, thermal inversions, natural sources of $\mathrm{CO_2}$ and particulates, indoor air pollutants including radon, control devices (catalytic converters, scrubbers, electrostatic precipitators, vapor recovery nozzles), acid deposition and buffering by limestone, and noise pollution.
   8 topics

   1. 7.1Introduction to Air Pollution
   2. 7.2Photochemical Smog
   3. 7.3Thermal Inversion
   4. 7.4Atmospheric CO₂ and Particulates
   5. 7.5Indoor Air Pollutants
   6. 7.6Reduction of Air Pollutants
   7. 7.7Acid Rain
   8. 7.8Noise Pollution

8. Unit 8

   Aquatic and Terrestrial Pollution

   7-10% of exam
   Pollution of water and land and its effects on ecosystems and people. Point and nonpoint sources, ranges of tolerance, coral reefs, oil spills, dead zones and the oxygen sag curve, heavy metals and methylmercury, endocrine disruptors, wetlands and mangroves, eutrophication, thermal pollution, persistent organic pollutants, bioaccumulation and biomagnification, solid waste and landfills, recycling and composting, sewage treatment, LD50 and dose-response curves, pollution and human health, and pathogens and infectious diseases.
   15 topics

   1. 8.1Sources of Pollution
   2. 8.2Human Impacts on Ecosystems
   3. 8.3Endocrine Disruptors
   4. 8.4Human Impacts on Wetlands and Mangroves
   5. 8.5Eutrophication
   6. 8.6Thermal Pollution
   7. 8.7Persistent Organic Pollutants (POPs)
   8. 8.8Bioaccumulation and Biomagnification
   9. 8.9Solid Waste Disposal
   10. 8.10Waste Reduction Methods
   11. 8.11Sewage Treatment
   12. 8.12Lethal Dose 50% (LD50)
   13. 8.13Dose Response Curve
   14. 8.14Pollution and Human Health
   15. 8.15Pathogens and Infectious Diseases

9. Unit 9

   Global Change

   15-20% of exam
   Local actions with global consequences, the most heavily weighted unit. Stratospheric ozone and its depletion by CFCs, replacements such as HFCs, the greenhouse effect and global warming potential, the threats from rising greenhouse gases, climate change evidence and feedback loops (especially in the Arctic), ocean warming and coral bleaching, ocean acidification, invasive species, endangered species, and the HIPPCO drivers of biodiversity loss with strategies to protect it.
   10 topics

   1. 9.1Stratospheric Ozone Depletion
   2. 9.2Reducing Ozone Depletion
   3. 9.3The Greenhouse Effect
   4. 9.4Increases in the Greenhouse Gases
   5. 9.5Global Climate Change
   6. 9.6Ocean Warming
   7. 9.7Ocean Acidification
   8. 9.8Invasive Species
   9. 9.9Endangered Species
   10. 9.10Human Impacts on Biodiversity

The exam, part by part

4 parts, 2 h 40 min in all.

• Section I: Multiple Choice

  Questions

  80

  Time

  1 h 30 min

  Weight

  60%

  Calculator allowed

  Format details

  Four answer choices (A-D), one point each, no penalty for guessing; about 67 seconds per question. A mix of individual questions and stimulus sets: 3-5 sets built on quantitative data (tables, charts, graphs; mainly Practice 5), 3-5 sets built on qualitative information (models, diagrams, maps; mainly Practice 2), and 2 sets built on a text source (mainly Practice 3). Unit weights: Unit 1 6-8%, Unit 2 6-8%, Units 3-6 10-15% each, Units 7-8 7-10% each, Unit 9 15-20%. Practice weights: Concept Explanation 30-38%, Visual Representations 12-19%, Text Analysis 6-8%, Scientific Experiments 2-4%, Data Analysis 12-19%, Mathematical Routines 6-9%, Environmental Solutions 17-23%. Calculator: four-function (with square root) or scientific handheld, or the built-in Desmos scientific calculator; no graphing calculators in 2027.

• Section II, Question 1: Design an Investigation

  Questions

  1

  Time

  23 min

  Weight

  13.3%

  Calculator allowed

  Format details

  Task types: Design an Investigation

  Section II is one 70-minute block for all three questions; Bluebook suggests about 22 minutes per question. Each question is 10 points, one third of the 40% free-response section.

• Section II, Question 2: Analyze and Interpret Quantitative Data

  Questions

  1

  Time

  23 min

  Weight

  13.3%

  Calculator allowed

  Format details

  Task types: Analyze and Interpret Quantitative Data

  Share of the 70-minute Section II. Built on a data table, chart, or graph; ends with propose-a-solution and justify rows.

• Section II, Question 3: Analyze an Environmental Problem Doing Calculations

  Questions

  1

  Time

  24 min

  Weight

  13.3%

  Calculator allowed

  Format details

  Task types: Analyze an Environmental Problem Doing Calculations

  Share of the 70-minute Section II. Usually three 2-point calculations (one point for a shown setup, one for the correct answer) plus content and solution rows.

Skills the exam scores

• 1.AConcept Explanation: describe concepts

  Describe environmental concepts and processes. Practice 1 (explaining concepts, processes, and models presented in writing) is 30-38% of the multiple-choice section and 13-20% of the free-response section.

• 1.BConcept Explanation: explain concepts

  Explain environmental concepts and processes: how or why they happen, as a cause-and-effect chain.

• 1.CConcept Explanation: explain in applied contexts

  Explain environmental concepts, processes, or models when they are placed inside a specific real-world scenario.

• 2.AVisual Representations: describe a visual

  Describe the characteristics of an environmental concept, process, or model shown in a diagram, map, or model. Practice 2 is 12-19% of the multiple-choice section and 6-10% of the free-response section.

• 2.BVisual Representations: explain relationships in a visual

  Explain relationships between different characteristics of a concept, process, or model represented visually, in theoretical and applied contexts.

• 2.CVisual Representations: connect a visual to broader issues

  Explain how the concepts and processes shown in a visual relate to broader environmental issues.

• 3.AText Analysis: identify the claim

  Identify the author's claim in a text source. Practice 3 is 6-8% of the multiple-choice section (two text-based sets) and is not explicitly assessed in the free-response section.

• 3.BText Analysis: perspective and assumptions

  Describe the author's perspective and the assumptions behind it.

• 3.CText Analysis: reasoning

  Describe the author's reasoning: how evidence is used to support the claim.

• 3.DText Analysis: credibility (not assessed)

  Evaluate the credibility of a source by recognizing bias and checking scientific accuracy. Taught in the course but not assessed on the AP Exam.

• 3.EText Analysis: validity of conclusions (not assessed)

  Evaluate whether a source or research study draws valid conclusions. Taught in the course but not assessed on the AP Exam.

• 4.AScientific Experiments: question or hypothesis

  Identify a testable hypothesis or scientific question for an investigation. Practice 4 is 2-4% of the multiple-choice section but 10-14% of the free-response section, concentrated in Question 1.

• 4.BScientific Experiments: identify the design

  Identify a research method, design, or measure used: the independent and dependent variables, the control, the constants.

• 4.CScientific Experiments: describe the design

  Describe an aspect of a research method, design, or measure, such as why a control is needed or how a variable was measured.

• 4.DScientific Experiments: collect data (not assessed)

  Make observations or collect data from laboratory setups. Practiced in labs but not assessed on the AP Exam.

• 4.EScientific Experiments: modified procedures

  Explain how a modification to an experimental procedure would alter the results.

• 5.AData Analysis: patterns and trends

  Describe patterns or trends in data from tables, charts, and graphs. Practice 5 is 12-19% of the multiple-choice section and 6-10% of the free-response section, anchored in Question 2.

• 5.BData Analysis: relationships among variables

  Describe relationships among variables in the data represented, such as a direct or inverse relationship.

• 5.CData Analysis: explain to draw conclusions

  Explain patterns and trends in data to draw conclusions.

• 5.DData Analysis: data and a hypothesis

  Interpret experimental data and results in relation to a given hypothesis: does the data support it, and which values show it?

• 5.EData Analysis: what the data implies

  Explain what the data implies or illustrates about an environmental issue.

• 6.AMathematical Routines: choose the approach

  Determine an approach or method aligned with the problem to be solved. Practice 6 is 6-9% of the multiple-choice section and 20% of the free-response section (the calculation points in Question 3).

• 6.BMathematical Routines: apply with work shown

  Apply appropriate mathematical relationships to solve a problem, with the work shown, for example by dimensional analysis. This is the setup point.

• 6.CMathematical Routines: accurate answer with units

  Calculate an accurate numeric answer with appropriate units. This is the answer point.

• 7.AEnvironmental Solutions: describe problems

  Describe environmental problems. Practice 7 is 17-23% of the multiple-choice section and 26-34% of the free-response section, the single largest share.

• 7.BEnvironmental Solutions: describe responses

  Describe potential responses or approaches to environmental problems.

• 7.CEnvironmental Solutions: tradeoffs

  Describe disadvantages, advantages, or unintended consequences of potential solutions.

• 7.DEnvironmental Solutions: use evidence

  Use data and evidence to support a potential solution.

• 7.EEnvironmental Solutions: propose a solution

  Make a claim that proposes a realistic solution to an environmental problem in an applied context.

• 7.FEnvironmental Solutions: justify a solution

  Justify a proposed solution by explaining its potential advantages.