Are flashcards effective for AP Environmental Science?

Yes. Flashcards use active recall — retrieving an answer from memory — which research shows is one of the most effective study methods, especially in short, spaced sessions. Because APES rewards instant recall of cycles, definitions, laws, and pollutants, the cards are an efficient way to make that knowledge automatic.

What topics do the APES flashcards cover?

All nine units: ecosystems and energy flow, biodiversity and succession, population dynamics, Earth systems, land and water use, energy resources, atmospheric pollution, aquatic and terrestrial pollution, and global change — including the carbon and nitrogen cycles, key environmental laws, and major pollutants.

How should I study with these APES flashcards?

Lead with the highest-weighted units — Global Change (Unit 9) and Units 3 through 6 (Populations, Earth Systems, Land and Water Use, and Energy). Mix the modes: flip to learn, type to test recall, match for speed, and quiz to check yourself before working full practice questions.

Are the AP Environmental Science flashcards free?

Yes — 100% free, all four study modes, no paywall.

Do these flashcards match the current AP Environmental Science course?

Yes. The cards are organized to the College Board's nine official AP Environmental Science units and reflect the current course and exam description, including the 1–5 score scale and the 80-question multiple-choice section.

Only about 10% of the energy at one trophic level is passed to the next; the rest (~90%) is lost as heat through cellular respiration.

A feeding position in a food chain: producers, primary consumers, secondary consumers, etc. Energy decreases at each higher level.

An organism that makes its own food, usually by photosynthesis (plants, algae); the base of the food chain.

A herbivore that eats producers (the second trophic level).

A carnivore that eats primary consumers (the third trophic level).

An organism (bacteria, fungi) that breaks down dead matter and recycles nutrients back into the ecosystem.

A network of interconnected food chains showing all the feeding relationships in a community.

Gross primary productivity (GPP)

The total rate at which producers capture and store energy through photosynthesis.

Net primary productivity (NPP)

GPP minus the energy producers use for their own respiration; the energy available to consumers.

A species with a disproportionately large effect on its community; removing it dramatically changes the ecosystem (e.g., sea otters).

The movement of an element through the living and nonliving parts of an ecosystem (carbon, nitrogen, phosphorus, water).

Photosynthesis removes CO₂ from the air; respiration, decomposition, and combustion return it. Oceans, soils, and fossil fuels are reservoirs.

Conversion of inert N₂ gas into ammonia (NH₃/NH₄⁺) usable by organisms — done by bacteria, lightning, and the Haber-Bosch process.

The bacterial conversion of ammonium (NH₄⁺) to nitrite (NO₂⁻) and then nitrate (NO₃⁻), the form plants use most easily.

The bacterial conversion of nitrate (NO₃⁻) back into N₂ gas, returning nitrogen to the atmosphere.

Moves phosphorus through rock, soil, and water with NO atmospheric (gas) phase; phosphorus often limits aquatic plant growth.

The nutrient in shortest supply that caps growth; nitrogen often limits land plants, phosphorus often limits aquatic ones.

Water moves through evaporation, transpiration, condensation, precipitation, runoff, and infiltration into aquifers.

Process where producers use sunlight, CO₂, and water to make glucose and release oxygen; it stores energy and removes CO₂.

Process where organisms break down glucose with oxygen to release energy, returning CO₂ to the atmosphere.

A diagram showing energy decreasing at each higher trophic level, with producers at the wide base.

A large region defined by its climate and characteristic plant and animal communities (e.g., tundra, desert, rainforest).

The variety of life at three levels — genetic, species, and ecosystem diversity. Higher diversity = more resilience.

The number of different species in a community.

How balanced the populations of different species are in a community.

The variety of genes within a species; greater diversity helps a species adapt to change and resist disease.

Free benefits ecosystems provide: pollination, water filtration, flood control, climate regulation, and food.

Ecological succession

The gradual, predictable change in a community over time after a disturbance, ending in a climax community.

Succession that begins on bare rock with no soil (after a glacier or lava flow); pioneer species are lichens and mosses.

Succession that rebuilds on existing soil after a disturbance (fire, abandoned farm); much faster than primary.

The first organisms to colonize a disturbed area (lichens, mosses, fast-growing weeds), which begin building soil.

A relatively stable, mature community in equilibrium with the local climate at the end of succession.

Resilience (ecological)

The ability of an ecosystem to recover after a disturbance; higher biodiversity generally increases resilience.

A species whose health reflects the condition of its environment (e.g., amphibians for water quality).

A species with a narrow niche and specific requirements (e.g., the panda); vulnerable to environmental change.

A species with a broad niche that can use many resources (e.g., raccoons); adaptable to change.

The role a species plays in its ecosystem — what it eats, where it lives, and how it interacts with others.

The theory that larger islands closer to the mainland support more species than small, remote ones.

A period when a large fraction of Earth's species go extinct over a short geologic time; Earth has had five.

A symbiotic relationship in which both species benefit (e.g., bees and flowers).

A relationship in which one species benefits and the other is unaffected (e.g., barnacles on a whale).

A relationship in which one species (the parasite) benefits at the host's expense.

Predator-prey relationship

An interaction where one organism hunts and eats another; their populations rise and fall in linked cycles.

The range of conditions (temperature, pH, salinity) an organism can survive; outside it, the organism cannot live.

Carrying capacity (K)

The maximum population size an environment can support indefinitely given its resources.

Your FREE AP Environmental Science Flashcards 2026 – 200+ Cards

Realistic AP Environmental Science flashcards across all nine units — flip, match, type, and quiz yourself on the cycles, laws, pollutants, and key concepts.

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AP Environmental Science Flashcards

The 10% rule: Only about 10% of the energy at one trophic level is passed to the next; the rest (~90%) is lost as heat through cellular respiration.
Trophic level: A feeding position in a food chain: producers, primary consumers, secondary consumers, etc. Energy decreases at each higher level.
Producer (autotroph): An organism that makes its own food, usually by photosynthesis (plants, algae); the base of the food chain.
Primary consumer: A herbivore that eats producers (the second trophic level).
Secondary consumer: A carnivore that eats primary consumers (the third trophic level).
Decomposer: An organism (bacteria, fungi) that breaks down dead matter and recycles nutrients back into the ecosystem.
Food web: A network of interconnected food chains showing all the feeding relationships in a community.
Gross primary productivity (GPP): The total rate at which producers capture and store energy through photosynthesis.
Net primary productivity (NPP): GPP minus the energy producers use for their own respiration; the energy available to consumers.
Keystone species: A species with a disproportionately large effect on its community; removing it dramatically changes the ecosystem (e.g., sea otters).
Biogeochemical cycle: The movement of an element through the living and nonliving parts of an ecosystem (carbon, nitrogen, phosphorus, water).
Carbon cycle: Photosynthesis removes CO₂ from the air; respiration, decomposition, and combustion return it. Oceans, soils, and fossil fuels are reservoirs.
Nitrogen fixation: Conversion of inert N₂ gas into ammonia (NH₃/NH₄⁺) usable by organisms — done by bacteria, lightning, and the Haber-Bosch process.
Nitrification: The bacterial conversion of ammonium (NH₄⁺) to nitrite (NO₂⁻) and then nitrate (NO₃⁻), the form plants use most easily.
Denitrification: The bacterial conversion of nitrate (NO₃⁻) back into N₂ gas, returning nitrogen to the atmosphere.
Phosphorus cycle: Moves phosphorus through rock, soil, and water with NO atmospheric (gas) phase; phosphorus often limits aquatic plant growth.
Limiting nutrient: The nutrient in shortest supply that caps growth; nitrogen often limits land plants, phosphorus often limits aquatic ones.
The water cycle: Water moves through evaporation, transpiration, condensation, precipitation, runoff, and infiltration into aquifers.
Photosynthesis: Process where producers use sunlight, CO₂, and water to make glucose and release oxygen; it stores energy and removes CO₂.
Cellular respiration: Process where organisms break down glucose with oxygen to release energy, returning CO₂ to the atmosphere.
Energy pyramid: A diagram showing energy decreasing at each higher trophic level, with producers at the wide base.
Biome: A large region defined by its climate and characteristic plant and animal communities (e.g., tundra, desert, rainforest).
Biodiversity: The variety of life at three levels — genetic, species, and ecosystem diversity. Higher diversity = more resilience.
Species richness: The number of different species in a community.
Species evenness: How balanced the populations of different species are in a community.
Genetic diversity: The variety of genes within a species; greater diversity helps a species adapt to change and resist disease.
Ecosystem services: Free benefits ecosystems provide: pollination, water filtration, flood control, climate regulation, and food.
Ecological succession: The gradual, predictable change in a community over time after a disturbance, ending in a climax community.
Primary succession: Succession that begins on bare rock with no soil (after a glacier or lava flow); pioneer species are lichens and mosses.
Secondary succession: Succession that rebuilds on existing soil after a disturbance (fire, abandoned farm); much faster than primary.
Pioneer species: The first organisms to colonize a disturbed area (lichens, mosses, fast-growing weeds), which begin building soil.
Climax community: A relatively stable, mature community in equilibrium with the local climate at the end of succession.
Resilience (ecological): The ability of an ecosystem to recover after a disturbance; higher biodiversity generally increases resilience.
Indicator species: A species whose health reflects the condition of its environment (e.g., amphibians for water quality).
Specialist species: A species with a narrow niche and specific requirements (e.g., the panda); vulnerable to environmental change.
Generalist species: A species with a broad niche that can use many resources (e.g., raccoons); adaptable to change.
Ecological niche: The role a species plays in its ecosystem — what it eats, where it lives, and how it interacts with others.
Island biogeography: The theory that larger islands closer to the mainland support more species than small, remote ones.
Mass extinction: A period when a large fraction of Earth's species go extinct over a short geologic time; Earth has had five.
Mutualism: A symbiotic relationship in which both species benefit (e.g., bees and flowers).
Commensalism: A relationship in which one species benefits and the other is unaffected (e.g., barnacles on a whale).
Parasitism: A relationship in which one species (the parasite) benefits at the host's expense.
Predator-prey relationship: An interaction where one organism hunts and eats another; their populations rise and fall in linked cycles.
Ecological tolerance: The range of conditions (temperature, pH, salinity) an organism can survive; outside it, the organism cannot live.
Carrying capacity (K): The maximum population size an environment can support indefinitely given its resources.
Exponential growth: J-shaped growth that occurs with unlimited resources; the population grows by a constant percent each interval.
Logistic growth: S-shaped growth that slows as a population nears its carrying capacity and limiting factors increase.
Density-dependent factor: A limiting factor that intensifies as population density rises: food shortage, disease, predation, competition.
Density-independent factor: A limiting factor that affects a population regardless of its density: weather, natural disasters, climate.
r-selected species: Species with many small offspring, little parental care, and short lives (insects, weeds); boom-and-bust populations.
K-selected species: Species with few large offspring, high parental care, and long lives (elephants, oaks); stable near carrying capacity.
Survivorship curve Type I: Most individuals survive to old age then die quickly (humans, large mammals).
Survivorship curve Type III: Most individuals die young in huge numbers; few survive to adulthood (fish, insects, plants).
Population growth rate formula: Growth rate = (births − deaths + immigration − emigration). For a simple rate: (births − deaths) ÷ 10 per 1,000.
Rule of 70: Doubling time (years) ≈ 70 ÷ the percent growth rate. A 2% growth rate doubles in about 35 years.
Demographic transition model: A four-stage model of how birth and death rates fall as a country develops.
Total fertility rate (TFR): The average number of children a woman has in her lifetime; about 2.1 is replacement level in developed nations.
Replacement-level fertility: The TFR (~2.1) at which a population exactly replaces itself, leading to stable size over time.
Age-structure diagram: A graph of a population by age and sex; a wide base predicts rapid growth, a narrow base predicts decline.
Infant mortality rate: The number of infant deaths per 1,000 live births; a key indicator of a country's development.
Doubling time: The time it takes a population to double in size, estimated with the rule of 70.
Limiting factor: Anything that restricts the size of a population, such as food, water, space, or predators.
Population crash (die-off): A sharp drop in numbers after a population overshoots its carrying capacity.
Biotic potential: The maximum reproductive rate of a population under ideal conditions.
Immigration vs. emigration: Immigration is individuals moving INTO a population; emigration is individuals moving OUT. Both change population size.
Demographic momentum: Continued population growth after fertility falls to replacement level, because of a large young population.
Plate tectonics: The movement of Earth's crustal plates, which causes earthquakes, volcanoes, and mountain-building at boundaries.
Soil horizon: A layer in a soil profile, from O (organic litter) and A (topsoil) at the top down to C and bedrock.
Soil texture: The proportion of sand, silt, and clay in soil; it controls water and nutrient holding. Loam is best for farming.
Loam: A balanced mix of sand, silt, and clay that holds water and nutrients well — ideal agricultural soil.
Troposphere: The lowest atmospheric layer where weather occurs and most air mass and water vapor are found.
Stratosphere: The atmospheric layer above the troposphere that contains the protective ozone layer.
Hadley cell: A global circulation cell where air rises at the equator (wet) and sinks around 30° latitude (dry, where deserts form).
Coriolis effect: The deflection of moving air and water by Earth's rotation, which shapes global wind belts and ocean currents.
El Niño: A periodic warming of the eastern Pacific that weakens trade winds, suppresses upwelling, and shifts global weather.
La Niña: The cool phase of ENSO with stronger trade winds and cooler eastern Pacific water — the opposite of El Niño.
Upwelling: The rise of cold, nutrient-rich water from the deep ocean to the surface, supporting productive fisheries.
Aquifer: An underground layer of permeable rock or sediment that stores and transmits groundwater.
Watershed: The land area that drains into a particular river, lake, or other body of water.
Albedo: The fraction of sunlight a surface reflects; ice and snow are high (reflective), dark land and ocean are low (absorbent).
Milankovitch cycles: Long-term natural variations in Earth's orbit and tilt that drive ice ages — a natural, not human, climate driver.
Weathering: The physical and chemical breakdown of rock at Earth's surface, the first step in soil formation.
Erosion: The transport of weathered soil and rock by water, wind, or ice; worsened by removing vegetation.
Salinization: The buildup of salts in soil from irrigation in dry climates, which reduces crop productivity.
Permeability: How easily water and air move through soil or rock; sandy soil is highly permeable, clay is not.
Thermohaline circulation: The global ocean conveyor belt driven by differences in water temperature and salinity (density).
Rain shadow: The dry region on the leeward side of a mountain, where descending air has lost its moisture.
Earthquake / Richter scale: Ground shaking from plate movement; the Richter (or moment magnitude) scale measures its energy.
Tragedy of the commons: The overuse of a shared, unregulated resource because individuals benefit while the cost of depletion is shared by all.
Green Revolution: The 20th-century increase in crop yields through fertilizer, irrigation, pesticides, and high-yield seed varieties.
Contour plowing: Plowing across a slope along its contour lines to reduce soil erosion and water runoff.
No-till farming: Planting without plowing, which keeps soil and moisture in place and stores carbon.
Crop rotation: Alternating the crops grown in a field to restore soil nitrogen and break pest cycles.
Integrated pest management (IPM): Combining biological, mechanical, and limited chemical controls to manage pests with less pesticide.
Monoculture: Growing a single crop over a large area; efficient but vulnerable to pests and hard on soil.
Overgrazing: Letting livestock eat vegetation faster than it regrows, leading to soil erosion and desertification.
Desertification: The degradation of once-productive land into desert, often from overgrazing, deforestation, or drought.
CAFO: Concentrated Animal Feeding Operation; raises many animals in a small area and generates large amounts of waste.
Sustainable yield: Harvesting a renewable resource no faster than it can replenish itself.
Surface (strip) mining: Removing surface layers to reach a shallow deposit; cheaper but highly destructive to the land.
Mountaintop removal: A form of surface mining that blasts off mountain tops to reach coal, burying streams with debris.
Subsurface mining: Tunneling underground to reach deep deposits; costlier and more dangerous than surface mining.
Mine reclamation: Restoring land after mining by regrading, replacing topsoil, and replanting vegetation.
Overfishing: Catching fish faster than populations can reproduce, leading to collapse; managed with catch limits.
Aquaculture: Farming fish and shellfish; boosts food supply but can pollute water and spread disease.
Clear-cutting: Removing all trees in an area at once; cheap but causes erosion and habitat loss.
Urban sprawl: The spread of low-density development outward from a city, consuming farmland and increasing car dependence.
Ecological footprint: The amount of productive land and water needed to supply a person's resources and absorb their waste.
Tragedy fix: regulation/ownership: Solutions to the tragedy of the commons: government quotas/regulation or assigning private ownership.
Buffer strip: A vegetated zone along a waterway that filters runoff and reduces fertilizer and sediment pollution.
Nonrenewable energy: Energy from finite stocks formed over millions of years: coal, oil, natural gas, and nuclear fuel.
Renewable energy: Energy from sources that replenish on a human timescale: solar, wind, hydro, geothermal, and biomass.
Fossil fuels: Coal, oil, and natural gas formed from buried ancient organisms; burning them releases CO₂ and pollutants.
Coal: The dirtiest fossil fuel; abundant and cheap but releases the most CO₂, SO₂, mercury, and particulates.
Natural gas: The cleanest-burning fossil fuel; releases less CO₂ than coal but leaks methane, a potent greenhouse gas.
Nuclear fission: Splitting uranium-235 atoms to release heat that boils water to spin a turbine; no CO₂ but radioactive waste.
Control rods: Rods in a nuclear reactor that absorb neutrons to slow or stop the fission chain reaction.
Nuclear meltdown: Overheating that melts a reactor core and can release radiation (e.g., Chernobyl, Fukushima).
Solar (photovoltaic) energy: Converting sunlight directly into electricity with solar cells; clean but intermittent.
Wind energy: Using turbines to convert wind into electricity; clean and renewable but intermittent and location-dependent.
Hydroelectric power: Generating electricity from flowing water, usually behind a dam; reliable but disrupts rivers and fish.
Geothermal energy: Using Earth's internal heat to generate electricity or heat buildings; steady and clean but location-limited.
Biomass energy: Burning organic material (wood, crops, waste) for energy; renewable but releases CO₂ and air pollutants.
Energy conservation: Reducing energy use through efficiency and behavior; the cheapest and cleanest 'source' of energy.
Energy efficiency: Getting more useful output from each unit of energy input (e.g., LED bulbs, hybrid cars).
Cogeneration (CHP): Capturing waste heat from electricity generation to use for heating, raising overall efficiency.
Fuel cell: A device that produces electricity from hydrogen and oxygen, emitting only water; clean but costly.
Cap and trade: A market policy that sets a pollution limit and lets companies buy and sell emission allowances.
Net energy yield: The usable energy from a source after subtracting the energy needed to produce it.
Tar sands / oil shale: Unconventional fossil fuels that are energy- and water-intensive to extract and process.
Fracking (hydraulic fracturing): Injecting high-pressure fluid to crack rock and release natural gas or oil; can contaminate groundwater.
Three Gorges / dam trade-offs: Large dams provide renewable power and flood control but flood habitat, displace people, and block fish.
Primary air pollutant: A pollutant emitted directly into the air (CO, SO₂, NOₓ, particulates, VOCs).
Secondary air pollutant: A pollutant that forms in the atmosphere from reactions of primary pollutants (e.g., ground-level ozone).
Photochemical smog: A brownish haze of ground-level ozone formed when sunlight reacts with NOₓ and VOCs on hot, sunny days.
Ground-level ozone: A harmful secondary pollutant in smog that damages lungs and crops — 'bad' ozone, nearby.
Thermal inversion: A layer of warm air over cooler air near the ground that traps pollutants and worsens smog.
Particulate matter (PM): Tiny solid or liquid particles in the air (soot, dust); PM2.5 lodges deep in the lungs and harms health.
Acid rain: Precipitation acidified by sulfuric and nitric acids formed when SO₂ and NOₓ react with water in the air.
Sulfur dioxide (SO₂): A pollutant from burning coal that contributes to acid rain and respiratory problems.
Nitrogen oxides (NOₓ): Pollutants from combustion that form smog and acid rain and contribute to ground-level ozone.
Carbon monoxide (CO): A colorless, odorless gas from incomplete combustion that binds hemoglobin and reduces oxygen delivery.
Volatile organic compounds (VOCs): Carbon compounds that evaporate easily (from fuels, paints, solvents) and help form photochemical smog.
Clean Air Act: The U.S. law that regulates air pollutants and sets National Ambient Air Quality Standards.
Scrubber: A smokestack device that removes SO₂ and particulates from exhaust gases before they reach the air.
Catalytic converter: A device on cars that converts CO, NOₓ, and VOCs in exhaust into less harmful gases.
Electrostatic precipitator: A device that uses an electric charge to remove particulates from smokestack exhaust.
Radon: A naturally occurring radioactive gas that seeps into buildings from soil; a leading cause of indoor lung cancer.
Asbestos: A fibrous mineral once used as insulation; inhaling its fibers causes lung disease and cancer.
Sick building syndrome: Health problems linked to poor indoor air quality in a building, from VOCs, mold, and poor ventilation.
Industrial (gray) smog: Smog from burning coal and oil, high in sulfur dioxide and particulates; common in industrial cities.
Indoor air pollution: Pollutants inside buildings (radon, CO, VOCs, mold, asbestos), often a greater health risk than outdoor air.
Noise pollution: Unwanted or harmful sound that can cause hearing loss and stress in humans and disrupt wildlife.
Lead (Pb) as a pollutant: A toxic metal once in gasoline and paint that harms the nervous system, especially in children.
Eutrophication: Nutrient enrichment of water (nitrogen, phosphorus) that triggers algal blooms; decay then depletes oxygen.
Cultural eutrophication: Human-accelerated eutrophication from fertilizer runoff, sewage, and detergents.
Dead zone (hypoxia): An area of water with too little dissolved oxygen to support most life, caused by eutrophication.
Point-source pollution: Pollution from a single identifiable source, such as a factory discharge pipe — easier to regulate.
Nonpoint-source pollution: Diffuse pollution from many sources, such as farm and street runoff — harder to control.
Biochemical oxygen demand (BOD): The amount of oxygen decomposers use to break down organic waste in water; high BOD starves water of oxygen.
Bioaccumulation: The buildup of a persistent toxin in one organism's tissues over its lifetime.
Biomagnification: The increase in a toxin's concentration at each higher trophic level, so top predators carry the most.
DDT: A persistent pesticide that biomagnified up food chains and thinned the eggshells of birds of prey like eagles.
Mercury (as a pollutant): A toxic metal from coal burning and mining that biomagnifies in fish and harms the nervous system.
Persistent organic pollutant (POP): A long-lasting, fat-soluble toxic chemical (DDT, PCBs) that biomagnifies and resists breakdown.
Dose-response curve: A graph showing how the harmful effect of a substance increases with the dose received.
LD50: The dose of a toxin that is lethal to 50% of a test population; a standard measure of toxicity.
Sanitary landfill: A lined and covered site for solid waste, designed to protect groundwater from leachate.
Leachate: Liquid that drains through a landfill, picking up contaminants that can pollute groundwater.
Incineration: Burning solid waste to reduce its volume and generate energy; releases air pollutants and ash.
The 3 Rs (reduce, reuse, recycle): The waste hierarchy: reduce consumption first, then reuse, then recycle before disposal.
Sewage treatment (primary): The first stage that physically removes solids from wastewater by screening and settling.
Sewage treatment (secondary): The biological stage that uses bacteria to break down dissolved organic waste in wastewater.
Thermal pollution: The release of heated water (often from power plants) that lowers dissolved oxygen and harms aquatic life.
Oil spill effects: Oil coats organisms and feathers, smothers habitats, and is hard to clean; harms birds, mammals, and fisheries.
Clean Water Act: The U.S. law that regulates pollutant discharges into surface waters and sets water-quality standards.
Greenhouse effect: Natural warming when greenhouse gases (CO₂, methane, water vapor, nitrous oxide) absorb and re-emit Earth's infrared heat.
Enhanced greenhouse effect: The extra warming caused by human emissions of greenhouse gases above natural levels.
Carbon dioxide (CO₂): The most abundant human-released greenhouse gas, mainly from burning fossil fuels and deforestation.
Methane (CH₄): A greenhouse gas that traps far more heat per molecule than CO₂ but is less abundant; from livestock, landfills, and gas leaks.
Global warming: The long-term rise in Earth's average surface temperature driven by the enhanced greenhouse effect.
Climate change: Long-term shifts in temperature and weather patterns, largely driven by human greenhouse-gas emissions.
Ocean acidification: The drop in ocean pH as CO₂ dissolves to form carbonic acid, harming coral and shell-building organisms.
Sea-level rise: The rise in ocean levels from melting land ice and the thermal expansion of warming seawater.
Positive feedback loop: A change that amplifies itself; melting ice lowers albedo, absorbing more heat and melting more ice.
Albedo feedback: As reflective ice melts it exposes dark land/ocean, which absorbs more heat and accelerates warming.
Ozone depletion: Thinning of the stratospheric ozone layer by chlorine from CFCs, letting more harmful UV reach the surface.
Chlorofluorocarbons (CFCs): Chemicals once used in refrigerants and aerosols that release ozone-destroying chlorine in the stratosphere.
Montreal Protocol: The 1987 treaty that phased out CFCs and is allowing the ozone layer to slowly recover — a major success.
Stratospheric vs. ground-level ozone: Stratospheric ozone protects life from UV ('good up high'); ground-level ozone is a pollutant ('bad nearby').
Invasive species: A non-native species that spreads rapidly and harms an ecosystem, often lacking natural predators (zebra mussels, kudzu).
HIPPCO: The drivers of biodiversity loss: Habitat destruction, Invasive species, Pollution, Population, Climate change, Overexploitation.
Habitat fragmentation: Breaking a large habitat into smaller, isolated patches, which reduces biodiversity and species movement.
Endangered species: A species at serious risk of extinction throughout all or much of its range.
Endangered Species Act: The U.S. law that protects threatened and endangered species and their critical habitat.
Tipping point: A threshold beyond which a system shifts abruptly and often irreversibly to a new state (e.g., a dying coral reef).
Kyoto Protocol / Paris Agreement: International agreements to reduce greenhouse-gas emissions and limit global warming.
Carbon footprint: The total greenhouse gases produced by a person, product, or activity, expressed as CO₂ equivalent.
Carbon sequestration: Capturing and storing atmospheric CO₂ in forests, soils, oceans, or underground to slow warming.
Deforestation and climate: Clearing forests removes a carbon sink and releases stored carbon, worsening global warming.

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By Career EmployerUpdated Sep 12, 2026

200+ free AP Environmental Science flashcards — 4 ways to study

AP Environmental Science Flashcard of the DayNew daily

The classic card. Do you know this one?

Click Study Flashcards above to open the flashcard hub — 200 AP Environmental Science cards you can flip, match, type, or quiz yourself on. Every card is drawn from the nine College Board APES units, so you study exactly what the exam measures.^[1] Pair them with our free practice test and study guide.

AP Environmental Science is one of the 17 AP exams — explore our AP flashcards to compare and prep across the whole family.

APES Flashcard Study Modes

Four modes run off the same 200 cards. Flip is for first-pass study, turning each term over to check the definition. Match times you pairing terms with their meanings. Type shows the definition and asks you to produce the term, so a card like Eutrophication has to come from memory. Quiz builds multiple-choice questions from the same deck for spot-checking.

Free AP Environmental Science flashcards from Career Employer — active recall for the APES exam

Why Flashcards Work for AP Environmental Science

Unit 9: Global Change is the biggest section at 24 cards, and it pulls vocabulary from every other unit into the climate picture. You get greenhouse drivers and feedback language such as Methane (CH₄) and Albedo feedback, plus consequence terms like Sea-level rise and Ozone depletion, and the memory device HIPPCO for the causes of biodiversity loss.

Unit 1: Ecosystems holds 22 cards on energy flow and nutrient cycling, with fronts such as The 10% rule, Trophic level, and Nitrification that reward precise numeric and stepwise definitions. Unit 2: Biodiversity adds another 22 cards on species interactions and community change, drilling distinctions like Commensalism versus Mutualism, along with Pioneer species and Species evenness.

Unit 3: Populations contributes 22 cards built around growth math and life strategies, including Rule of 70, Logistic growth, and the contrast between r-selected species and K-selected species. Unit 4: Earth Systems & Resources covers 22 cards on soil, water, and ocean-atmosphere patterns, with fronts like Loam, Upwelling, and El Niño that are easy to confuse under time pressure.

Unit 5: Land & Water Use offers 22 cards on agricultural and land management practice, including CAFO, Monoculture, and Buffer strip. Unit 6: Energy Resources matches that with 22 cards spanning fuels, reactors, and policy tools, so Control rods, Cap and trade, and Biomass energy sit in the same rotation.

Unit 7: Atmospheric Pollution runs 22 cards on pollutants, control technology, and legislation, with Thermal inversion, Scrubber, and Clean Air Act among the fronts. Unit 8: Aquatic & Terrestrial Pollution closes the deck with 22 cards on toxicology and waste, drilling LD50, Biomagnification, and Leachate.

APES rewards instant recall of the carbon and nitrogen cycles, environmental laws, pollutants, and key definitions.^[2] Spaced flashcards are the most efficient way to make that knowledge automatic. Used alongside our practice test and study guide, they turn review time into measurable progress.

APES Flashcards by Unit

The cards are organized by the nine College Board units. Drill the highest-weighted ones first — Global Change anchors the exam, and Units 3 through 6 together make up roughly half of it:^[1]

AP Environmental Science flashcards by unit
Unit	Topic
Unit 1	The Living World: Ecosystems
Unit 2	The Living World: Biodiversity
Unit 3	Populations
Unit 4	Earth Systems and Resources
Unit 5	Land and Water Use
Unit 6	Energy Resources and Consumption
Unit 7	Atmospheric Pollution
Unit 8	Aquatic and Terrestrial Pollution
Unit 9	Global Change

How to Get the Most Out of These Flashcards

Start with Unit 9: Global Change. At 24 cards it is the largest section and it recycles terms from the pollution, energy, and biodiversity units, so it doubles as review.
Type-drill the quantitative cards. The 10% rule and Rule of 70 need exact wording and numbers, and typing them forces recall that flipping quietly lets you skip.
Use Match for the interaction and lookalike terms. Pairing Mutualism, Parasitism, and Commensalism against their definitions under a clock exposes which ones you only half know.
Move to the practice test once Quiz holds steady. When multiple choice stops surprising you across all nine units, shift to full questions and use the study guide for the gaps.
Work two units per sitting. With 200 cards split into nine units, a pair of units per session keeps rotations short and brings every label back around quickly.

AP Environmental Science Flashcards FAQ

Two hundred free AP Environmental Science (APES) flashcards, organized across all nine College Board units — from ecosystems, biodiversity, and populations through Earth systems, land and water use, energy, pollution, and global change. They're free with no account required.

References

1.College Board. “AP Environmental Science Course and Exam Description.” College Board. ↑
2.U.S. Environmental Protection Agency. “Environmental Topics.” U.S. EPA. ↑
3.U.S. Geological Survey. “The Carbon Cycle.” USGS. ↑

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