AP Environmental Science Exam — Questions and Answers

Question 1: What is 'disaster risk reduction' (DRR) in the context of environmental hazard management?

Insurance programs that compensate communities after a disaster occurs
Emergency response coordination immediately after a hazard event
Systematic efforts to analyze and reduce risk factors that lead to disasters (Correct answer)
The process of relocating entire communities away from hazard zones permanently

Correct answer: Systematic efforts to analyze and reduce risk factors that lead to disasters

Disaster risk reduction encompasses proactive policies, assessments, and measures aimed at preventing new risks and reducing existing vulnerabilities before a hazard event strikes.

Question 2: What is the primary source of energy for most ecosystems on Earth?

Geothermal heat
Water
Sunlight (Correct answer)
Wind

Correct answer: Sunlight

Sunlight is captured by photosynthetic organisms and forms the foundation of most food webs.

Question 3: Which U.S. law regulates the transportation, storage, and disposal of hazardous waste from 'cradle to grave'?

Clean Water Act
CERCLA
RCRA (Correct answer)
TSCA

Correct answer: RCRA

The Resource Conservation and Recovery Act (RCRA) establishes a framework for managing hazardous waste throughout its lifecycle.

Question 4: Which type of ecological relationship exists between a lion and a zebra?

Commensalism
Predation (Correct answer)
Competition
Mutualism

Correct answer: Predation

Predation is a relationship where one organism (predator) kills and eats another (prey) for energy.

Question 5: Endocrine disruptors are chemicals that pose health risks primarily by:

Mimicking, blocking, or interfering with the body's hormonal signaling systems (Correct answer)
Causing rapid mutations in endocrine gland DNA, leading to cancer
Directly destroying hormone-producing glands like the thyroid or adrenals
Replacing iodine in thyroid hormones, impairing metabolism

Correct answer: Mimicking, blocking, or interfering with the body's hormonal signaling systems

Endocrine disruptors interfere with synthesis, secretion, transport, binding, or elimination of natural hormones, disrupting development, reproduction, and metabolism.

Question 6: What is desalination, and what is its primary environmental concern?

Removing salt from water; produces brine waste harmful to marine ecosystems (Correct answer)
Adding minerals to purified water; may alter water taste
Filtering sediment; disrupts river flow
Treating wastewater; requires large energy inputs

Correct answer: Removing salt from water; produces brine waste harmful to marine ecosystems

Desalination converts seawater to freshwater but produces concentrated brine that can harm marine environments when discharged.

Question 7: What is the zone of an aquatic ecosystem where photosynthesis can occur due to sufficient light penetration?

Abyssal zone
Benthic zone
Aphotic zone
Photic zone (Correct answer)

Correct answer: Photic zone

The photic zone is the sunlit upper layer of water where enough light exists for photosynthesis.

Question 8: The primary environmental concern associated with coal combustion is:

Depletion of stratospheric ozone
Radioactive waste generation
Emission of sulfur dioxide, nitrogen oxides, mercury, and CO2 (Correct answer)
Thermal pollution of rivers

Correct answer: Emission of sulfur dioxide, nitrogen oxides, mercury, and CO2

Coal combustion emits SO2 (acid rain), NOx (smog/acid rain), mercury (neurotoxin), particulates, and large quantities of CO2 (climate change).

Question 9: What is the term for the total mass of living organisms in a given area or trophic level?

Standing crop
Net primary productivity
Biodensity
Biomass (Correct answer)

Correct answer: Biomass

Biomass refers to the total mass of living biological organisms in a particular area or ecosystem.

Question 10: Second-generation biofuels differ from first-generation biofuels in that they:

Are produced from food crops like corn and sugarcane rather than waste biomass
Use the same fermentation processes as first-generation but with more efficient yeast strains
Are derived from non-food feedstocks (cellulosic biomass, agricultural residues, algae) that don't compete with food production (Correct answer)
Are liquid fuels burned in conventional engines without any engine modification

Correct answer: Are derived from non-food feedstocks (cellulosic biomass, agricultural residues, algae) that don't compete with food production

Second-generation (advanced) biofuels use lignocellulosic feedstocks (switchgrass, wood chips, corn stover, municipal solid waste) or algae, avoiding the food vs. fuel conflict of corn ethanol and sugarcane ethanol.

Question 11: Which process removes dissolved oxygen from water, harming aquatic life, often caused by excess nutrient runoff?

Salinization
Sedimentation
Eutrophication (Correct answer)
Acidification

Correct answer: Eutrophication

Eutrophication occurs when nutrient overload triggers algal blooms that deplete oxygen as they decompose.

Question 12: Which type of drought is defined by a deficiency of precipitation over an extended period?

Hydrological drought
Socioeconomic drought
Agricultural drought
Meteorological drought (Correct answer)

Correct answer: Meteorological drought

A meteorological drought is defined purely in terms of the degree of dryness compared to normal precipitation levels over a defined period.

Question 13: Desertification of agricultural land is most commonly caused by:

Mining activities that compact soil and prevent water infiltration
Industrial pollution from nearby factories
Natural climate cycles that periodically dry out large regions
Overgrazing, unsustainable cultivation, and deforestation that degrade dryland soils (Correct answer)

Correct answer: Overgrazing, unsustainable cultivation, and deforestation that degrade dryland soils

Land degradation in arid and semi-arid areas - driven by overgrazing, poor cultivation, and vegetation removal - reduces soil fertility and vegetation cover, eventually converting productive land to desert-like conditions.

Question 14: What is the primary driver of global biodiversity loss today?

Climate change
Pollution
Overexploitation of wildlife
Habitat destruction and land use change (Correct answer)

Correct answer: Habitat destruction and land use change

Habitat destruction and land conversion for agriculture, urban development, and other uses is the leading cause of global species loss.

Question 15: Which concept describes the minimum viable population (MVP) in conservation?

The optimal breeding population for captive programs
The population level at which a species is removed from the endangered list
The maximum population a habitat can support
The smallest population size with a high probability of persisting long-term (Correct answer)

Correct answer: The smallest population size with a high probability of persisting long-term

MVP is the smallest population size estimated to have a reasonable chance of surviving genetic, demographic, and environmental stochasticity.

Question 16: Which climate adaptation strategy involves restoring coastal wetlands to buffer communities from storm surges?

Green infrastructure (Correct answer)
Demand-side management
Geoengineering
Carbon trading

Correct answer: Green infrastructure

Green infrastructure uses natural and engineered systems (wetlands, mangroves) to reduce vulnerability to climate impacts.

Question 17: Acid rain is primarily caused by atmospheric reactions involving which two gases?

SO₂ and NOₓ (Correct answer)
HFCs and PFCs
O₃ and CO
CO₂ and CH₄

Correct answer: SO₂ and NOₓ

SO₂ and NOₓ emitted from power plants and vehicles react with water vapor to form sulfuric and nitric acids.

Question 18: Which phenomenon involves unusual warming of the central and eastern Pacific Ocean, disrupting global weather patterns?

La Niña
El Niño (Correct answer)
North Atlantic Oscillation
Arctic Oscillation

Correct answer: El Niño

El Niño is a periodic warming of Pacific surface waters that shifts rainfall patterns and can cause droughts and floods globally.

Question 19: Biomagnification refers to the process by which:

Pesticides in soil are absorbed by plant roots and concentrated in leaves
Bacteria break down organic pollutants into more toxic compounds
Contaminants become more concentrated at each successive level of a food chain (Correct answer)
Pollutants evaporate from tropical regions and condense in polar areas

Correct answer: Contaminants become more concentrated at each successive level of a food chain

Lipophilic (fat-soluble) pollutants like PCBs, DDT, and methylmercury accumulate in fatty tissues and increase in concentration with each trophic level because organisms consume many prey items over their lifetime.

Question 20: What is phytoremediation?

Using animals to control invasive plant species
Photosynthesis-based energy production for cleanup
Using plants to absorb, contain, or detoxify soil pollutants (Correct answer)
Treating water with plant extracts

Correct answer: Using plants to absorb, contain, or detoxify soil pollutants

Phytoremediation uses hyperaccumulator plants to absorb heavy metals and other contaminants from soil and water.

Question 21: An offshore wind farm generally produces more electricity per unit of installed capacity than an onshore wind farm because:

Ocean temperatures moderate the air density, increasing turbine efficiency
Offshore wind speeds are higher and more consistent due to reduced surface friction and fewer obstructions (Correct answer)
Offshore turbines use larger blades that are prohibited in many onshore locations
Salt water conducts electricity better, reducing transmission losses

Correct answer: Offshore wind speeds are higher and more consistent due to reduced surface friction and fewer obstructions

Oceans have low surface roughness, fewer turbulence-causing obstacles, and higher average wind speeds - improving capacity factors from ~25-40% onshore to ~40-55% offshore.

Question 22: The competitive exclusion principle states that two species competing for identical resources cannot:

Occupy different niches
Share a predator
Coexist indefinitely (Correct answer)
Evolve together

Correct answer: Coexist indefinitely

Gause's principle holds that two species with the same niche cannot coexist; one will outcompete the other.

Question 23: Which gas is responsible for the stratospheric ozone hole primarily observed over Antarctica?

Nitrous oxide
Methane
Carbon dioxide
Chlorofluorocarbons (CFCs) (Correct answer)

Correct answer: Chlorofluorocarbons (CFCs)

CFC molecules release chlorine in the stratosphere, which catalytically destroys ozone molecules in cold polar vortex conditions.

Question 24: Which type of symbiosis benefits one organism while the other is neither harmed nor helped?

Competition
Commensalism (Correct answer)
Mutualism
Parasitism

Correct answer: Commensalism

Commensalism describes a relationship where one organism benefits and the other is unaffected.

Question 25: U.S. EPA's Superfund program (CERCLA) was established to:

Provide grants to states for wastewater treatment plant construction
Clean up the nation's most hazardous abandoned waste sites and assign cleanup costs to responsible parties (Correct answer)
Fund air quality monitoring stations across the country
Regulate the disposal of municipal solid waste in landfills

Correct answer: Clean up the nation's most hazardous abandoned waste sites and assign cleanup costs to responsible parties

CERCLA (1980) created the Superfund to finance cleanup of contaminated sites and empowered EPA to hold potentially responsible parties (PRPs) liable for cleanup costs.

Question 26: Thermal pollution of waterways primarily harms aquatic life by:

Reducing dissolved oxygen levels (Correct answer)
Increasing water salinity
Increasing water turbidity
Introducing heavy metals

Correct answer: Reducing dissolved oxygen levels

Warmer water holds less dissolved oxygen, stressing or killing fish and other aerobic aquatic organisms.

Question 27: The Clean Water Act requires municipalities to obtain which type of permit for wastewater discharges?

NPDES permit (Correct answer)
CAA operating permit
CERCLA authorization
RCRA permit

Correct answer: NPDES permit

The National Pollutant Discharge Elimination System (NPDES) permit program regulates point source discharges into U.S. waters.

Question 28: What is the global warming potential (GWP) of methane compared to CO₂ over a 100-year timeframe?

About equal
About 28–36 times greater (Correct answer)
About 5 times greater
About 300 times greater

Correct answer: About 28–36 times greater

Methane's 100-year GWP is approximately 28–36 times that of CO₂, making it a potent but shorter-lived greenhouse gas.

Question 29: Lithium-ion batteries are currently the dominant technology for grid-scale and electric vehicle energy storage primarily because:

Lithium-ion batteries have no safety risks and require no thermal management
They offer high energy density, long cycle life, and rapidly declining costs driven by manufacturing scale (Correct answer)
They can be fully charged and discharged infinitely without capacity degradation
Lithium is the most abundant mineral on Earth, ensuring low material costs

Correct answer: They offer high energy density, long cycle life, and rapidly declining costs driven by manufacturing scale

Li-ion batteries have high gravimetric/volumetric energy density, high round-trip efficiency (~90-95%), long cycle life, and costs that have fallen ~97% since 1991 due to manufacturing scale from the consumer electronics and EV industries.

Question 30: What is the primary cause of saltwater intrusion into coastal freshwater aquifers?

Sea turtle migrations
Increased rainfall
Storm surges during hurricanes
Over-pumping of groundwater (Correct answer)

Correct answer: Over-pumping of groundwater

Excessive groundwater pumping lowers water table pressure, allowing denser saltwater from the ocean to move inland.

Question 31: What is the main environmental advantage of municipal solid waste incineration over landfilling?

Lower operating costs
No air emissions
Significant volume reduction and energy recovery (Correct answer)
Elimination of all toxins

Correct answer: Significant volume reduction and energy recovery

Incineration reduces waste volume by up to 90% and can generate electricity, though it requires strict emission controls.

Question 32: The tragedy of the anticommons (complementary to Hardin's commons tragedy) describes:

The collapse of ecosystem services when too many stakeholders attempt to manage them simultaneously
The underuse of a resource when too many owners each hold veto rights, preventing anyone from using it productively (Correct answer)
The destruction of public goods by private companies seeking profit
The excessive protection of rare species that prevents sustainable harvesting

Correct answer: The underuse of a resource when too many owners each hold veto rights, preventing anyone from using it productively

The anticommons (Heller, 1998) occurs when too many parties hold the right to exclude others from a resource, leading to underuse - seen in patent thickets, fragmented land ownership, and pharmaceutical research.

Question 33: Which trophic level consists of organisms that convert solar energy into chemical energy?

Secondary consumers
Decomposers
Primary consumers
Producers (Correct answer)

Correct answer: Producers

Producers (plants, algae, cyanobacteria) fix solar energy via photosynthesis and form the base of the food chain.

Question 34: Lead poisoning in children is particularly harmful because:

Lead is released into breast milk, exposing infants during nursing
Children's smaller body mass makes the same dose proportionally more toxic
Lead permanently interferes with neurological development, causing irreversible cognitive and behavioral damage (Correct answer)
Children absorb lead through skin contact more readily than adults do

Correct answer: Lead permanently interferes with neurological development, causing irreversible cognitive and behavioral damage

Lead permanently damages the developing nervous system - reducing IQ, causing learning disabilities, behavioral problems, and reduced hearing - with no safe blood lead level established for children.

Question 35: Which process converts organic waste into nutrient-rich soil amendment through microbial decomposition?

Pyrolysis
Composting (Correct answer)
Landfilling
Incineration

Correct answer: Composting

Composting harnesses aerobic microorganisms to break down organic matter into humus-rich material useful for soil amendment.

Question 36: Which farming practice best describes no-till agriculture and its primary environmental benefit?

Irrigating crops only when soil moisture sensors indicate water stress
Rotating crops annually to prevent nutrient depletion in the soil
Seeding crops directly into undisturbed soil, preserving soil structure and reducing erosion (Correct answer)
Planting crops without using any synthetic fertilizers, relying on natural soil nutrients

Correct answer: Seeding crops directly into undisturbed soil, preserving soil structure and reducing erosion

No-till (conservation tillage) leaves crop residues on the surface and disturbs the soil as little as possible during planting, dramatically reducing erosion and retaining soil moisture and carbon.

Question 37: The Convention on Biological Diversity (CBD) established which global target framework for protecting biodiversity by 2030?

REDD+
Kunming-Montreal Global Biodiversity Framework (Correct answer)
Aichi Biodiversity Targets
Paris Biodiversity Agreement

Correct answer: Kunming-Montreal Global Biodiversity Framework

The Kunming-Montreal Global Biodiversity Framework (2022) includes the '30×30' target to protect 30% of land and ocean by 2030.

Question 38: Which U.S. federal law governs the cleanup of contaminated hazardous waste sites?

Clean Water Act
CERCLA (Superfund) (Correct answer)
RCRA
TSCA

Correct answer: CERCLA (Superfund)

CERCLA (Comprehensive Environmental Response, Compensation, and Liability Act), known as Superfund, funds hazardous site cleanup.

Question 39: The circular economy model differs from the traditional linear economy in that:

A circular economy focuses only on recycling at end of life rather than the full production process
A circular economy is driven exclusively by government mandates rather than market incentives
A circular economy designs out waste by keeping materials in productive use through reuse, repair, remanufacturing, and recycling (Correct answer)
A circular economy requires all products to be made from biological materials that decompose naturally

Correct answer: A circular economy designs out waste by keeping materials in productive use through reuse, repair, remanufacturing, and recycling

The circular economy moves from the take-make-dispose linear model to closed loops: products and materials are designed for longevity, repair, remanufacture, and ultimately recycling, minimizing waste and virgin resource extraction.

Question 40: Which type of natural hazard is primarily caused by the movement of tectonic plates along fault lines?

Wildfires
Droughts
Hurricanes
Earthquakes (Correct answer)

Correct answer: Earthquakes

Earthquakes are caused by the sudden release of energy as tectonic plates slip or fracture along fault lines.

Question 41: Which contaminant, naturally occurring in some well water, has been linked to cancer and is regulated by the Safe Drinking Water Act?

Magnesium
Arsenic (Correct answer)
Chlorine
Fluoride

Correct answer: Arsenic

Arsenic occurs naturally in some aquifers and, at elevated concentrations, is a known human carcinogen regulated under the SDWA.

Question 42: In a food chain, approximately what percentage of energy is transferred from one trophic level to the next?

1%
90%
10% (Correct answer)
50%

Correct answer: 10%

The 10% rule states that only about 10% of energy is passed to the next trophic level; the rest is lost as heat.

Question 43: Cogeneration (combined heat and power) improves energy efficiency by:

Capturing waste heat from electricity generation for useful heating (Correct answer)
Using two types of fuel simultaneously
Generating electricity from two separate turbines
Mixing fossil fuels with biofuels

Correct answer: Capturing waste heat from electricity generation for useful heating

Cogeneration captures the heat that would otherwise be wasted in conventional power generation and uses it for space or process heating.

Question 44: Concentrated Solar Power (CSP) differs from photovoltaic (PV) solar in that CSP:

Uses mirrors or lenses to concentrate sunlight as heat to drive a conventional steam turbine (Correct answer)
Requires direct contact with sunlight and cannot use diffuse radiation
Generates electricity only during brief periods of peak solar irradiance
Converts sunlight directly into electricity using semiconductor materials

Correct answer: Uses mirrors or lenses to concentrate sunlight as heat to drive a conventional steam turbine

CSP concentrates sunlight to produce high-temperature heat used in a conventional thermodynamic power cycle (steam or Stirling engine), and can incorporate thermal storage to dispatch power after sunset.

Question 45: The U.S. National Environmental Policy Act (NEPA) requires federal agencies to:

Ban development in federally designated wilderness areas
Purchase carbon offsets for all government operations
Prepare an Environmental Impact Statement (EIS) for major federal actions significantly affecting the environment (Correct answer)
Set binding emission limits for all industrial facilities

Correct answer: Prepare an Environmental Impact Statement (EIS) for major federal actions significantly affecting the environment

NEPA (1970) mandates Environmental Impact Statements for significant federal actions, ensuring environmental consequences are analyzed before decisions are made.

Question 46: The primary route of human exposure to methylmercury is through:

Contact with mercury-containing thermometers or fluorescent light bulbs
Consuming fish and shellfish, particularly large predatory marine fish (Correct answer)
Drinking groundwater contaminated by industrial mercury discharges
Breathing air near coal-burning power plants

Correct answer: Consuming fish and shellfish, particularly large predatory marine fish

Inorganic mercury from industrial sources is methylated by anaerobic bacteria, enters aquatic food chains, and biomagnifies; large predatory fish (tuna, swordfish, shark) accumulate highest concentrations.

Question 47: What is the term for species that significantly shape their community's structure, often out of proportion to their abundance?

Keystone species (Correct answer)
Endemic species
Invasive species
Pioneer species

Correct answer: Keystone species

Keystone species have a disproportionately large effect on their ecosystem relative to their biomass or numbers.

Question 48: Which energy source accounts for the largest share of global primary energy consumption?

Renewable energy
Natural gas
Nuclear power
Petroleum and other liquids (Correct answer)

Correct answer: Petroleum and other liquids

Petroleum and other liquids remain the largest source of global primary energy, used heavily in transportation and industry.

Question 49: Which of the following is a primary environmental concern associated with utility-scale solar PV installations?

Electromagnetic radiation from solar panels that harms wildlife in surrounding areas
Release of silicon dioxide dust from panel surfaces causing respiratory hazards
Land use impacts and habitat disruption in desert ecosystems, plus waste from end-of-life panel disposal (Correct answer)
Significant noise pollution from inverter operation affecting nearby communities

Correct answer: Land use impacts and habitat disruption in desert ecosystems, plus waste from end-of-life panel disposal

Large solar farms require significant land area (5-10 acres/MW), potentially displacing desert tortoises, plant communities, and other sensitive species; end-of-life panels contain cadmium, lead, and other materials requiring careful disposal.

Question 50: Life Cycle Assessment (LCA) is a tool that evaluates:

The lifecycle of regulatory permits from application through renewal and cancellation
The environmental impacts of a product or process across its entire life from raw material extraction through production, use, and disposal (Correct answer)
The career trajectory of environmental professionals from entry level to executive positions
The expected operational lifespan of industrial equipment before replacement is needed

Correct answer: The environmental impacts of a product or process across its entire life from raw material extraction through production, use, and disposal

LCA (standardized in ISO 14040/14044) systematically quantifies the environmental inputs (energy, water, materials) and outputs (emissions, waste) of a product system across its full life cycle.

Question 51: What is the primary mechanism by which volcanic eruptions can cause short-term global cooling?

Sulfur dioxide emissions form sulfate aerosols in the stratosphere that reflect sunlight (Correct answer)
Ash particles trap outgoing infrared radiation, causing a greenhouse effect
The heat released by lava flows warms the upper atmosphere, causing circulation changes
Carbon dioxide from eruptions acidifies clouds, reducing their reflectivity

Correct answer: Sulfur dioxide emissions form sulfate aerosols in the stratosphere that reflect sunlight

Large eruptions inject sulfur dioxide into the stratosphere, where it converts to sulfate aerosols that scatter incoming solar radiation, temporarily reducing surface temperatures globally.

Question 52: Which treaty regulates international trade in endangered species?

Ramsar Convention
Bern Convention
CITES (Correct answer)
Convention on Biological Diversity (CBD)

Correct answer: CITES

CITES (Convention on International Trade in Endangered Species) lists species and controls or bans international commercial trade in them.

Question 53: The Hubbert Peak theory predicts that:

Coal consumption will peak due to environmental regulations
Renewable energy will surpass fossil fuels by 2050
Nuclear energy will plateau as uranium reserves are exhausted
Global oil production will eventually reach a maximum and then decline (Correct answer)

Correct answer: Global oil production will eventually reach a maximum and then decline

M. King Hubbert predicted in 1956 that oil production in any region follows a bell-shaped curve, rising to a peak then declining as reserves deplete.

Question 54: The Environmental Kuznets Curve (EKC) hypothesis suggests that:

Wealthier countries always have better environmental conditions than poorer countries
Environmental pollution initially increases as a country develops economically but decreases after a certain income threshold (Correct answer)
Economic growth and environmental protection are always mutually exclusive goals
Environmental degradation is linearly proportional to economic growth in all countries

Correct answer: Environmental pollution initially increases as a country develops economically but decreases after a certain income threshold

The EKC (Grossman and Krueger, 1991) proposes an inverted-U relationship between per-capita income and pollution: at low incomes, development increases pollution; beyond a turning point, higher incomes support cleaner technology and environmental regulation.

Question 55: Industrial ecology is best described as a field that:

Studies the ecological impacts of industrial facilities on surrounding natural habitats
Regulates industrial pollution through ecological risk assessment frameworks
Replaces conventional industries with biological production methods like fermentation
Analyzes material and energy flows through industrial systems to optimize resource use and minimize waste by mimicking natural ecosystems (Correct answer)

Correct answer: Analyzes material and energy flows through industrial systems to optimize resource use and minimize waste by mimicking natural ecosystems

Industrial ecology uses the biological ecosystem as a model for industrial systems: one firm's waste becomes another's input (industrial symbiosis), closing material loops and reducing virgin resource demand and waste generation.

Question 56: Which biome is characterized by permafrost, low precipitation, and very short growing seasons?

Tundra (Correct answer)
Taiga
Grassland
Temperate deciduous forest

Correct answer: Tundra

The tundra biome has permanently frozen subsoil (permafrost) and supports only low-growing vegetation.

Question 57: What does BOD (Biochemical Oxygen Demand) measure in water quality assessment?

The concentration of nitrogen compounds
The amount of dissolved oxygen in water
The amount of oxygen consumed by microbes decomposing organic matter (Correct answer)
The biological diversity of a water body

Correct answer: The amount of oxygen consumed by microbes decomposing organic matter

BOD measures how much oxygen microorganisms use to decompose organic waste, indicating the level of organic pollution.

Question 58: What is gray water?

Water with high sediment content
Highly contaminated industrial wastewater
Reclaimed water from sewage treatment plants
Lightly used household water from sinks and showers, not toilets (Correct answer)

Correct answer: Lightly used household water from sinks and showers, not toilets

Gray water is relatively clean wastewater from bathroom sinks, showers, and laundry that can be recycled for irrigation.

Question 59: The process by which nitrogen-fixing bacteria convert atmospheric N₂ into ammonia is called:

Nitrification
Denitrification
Ammonification
Nitrogen fixation (Correct answer)

Correct answer: Nitrogen fixation

Nitrogen fixation converts inert atmospheric nitrogen gas into biologically available ammonia (NH₃).

Question 60: What does the concept of decoupling mean in the context of sustainable development?

Separating environmental management from economic planning in government decision-making
Disconnecting global supply chains to reduce transportation-related emissions
Achieving economic growth while simultaneously reducing environmental impacts such as resource use or emissions (Correct answer)
Separating carbon capture from energy generation to improve industrial efficiency

Correct answer: Achieving economic growth while simultaneously reducing environmental impacts such as resource use or emissions

Decoupling means that economic growth (GDP increase) is accompanied by a reduction (or slower growth) in environmental pressure - resource use, emissions, or waste - breaking the historic linkage between prosperity and pollution.

Question 61: Monoculture farming poses environmental risks primarily because:

Single crops deplete soil carbon faster than no-till methods
Genetic uniformity increases vulnerability to pests, diseases, and climate variability (Correct answer)
Monocultures cannot be harvested by mechanized equipment
It requires more land than polyculture for the same yield

Correct answer: Genetic uniformity increases vulnerability to pests, diseases, and climate variability

A single genetically uniform crop planted over large areas is highly vulnerable to a single pathogen or pest that overcomes its defenses, risking crop failures.

Question 62: Nitrate contamination of drinking water poses the greatest health risk to:

Pregnant women, for whom nitrates interfere with folic acid absorption
Infants under 6 months of age, who are at risk of methemoglobinemia (Correct answer)
Athletes who consume large quantities of water during exercise
Elderly people with weakened kidney function

Correct answer: Infants under 6 months of age, who are at risk of methemoglobinemia

In infants, gut bacteria convert nitrate to nitrite; nitrite oxidizes hemoglobin to methemoglobin (unable to carry oxygen), causing blue baby syndrome (methemoglobinemia).

Question 63: The rebound effect in energy economics refers to:

Grid stabilization after a power outage
Increased energy consumption that offsets efficiency gains when energy services become cheaper (Correct answer)
The bounce-back in renewable energy investment after a recession
The recovery of energy prices after an oil shock

Correct answer: Increased energy consumption that offsets efficiency gains when energy services become cheaper

When efficiency improvements lower the cost of using energy, people tend to use more energy services, partially or fully canceling the expected savings.

Question 64: Agroforestry differs from conventional agriculture in that it:

Applies forest management techniques like selective logging to annual croplands
Uses hydroponics to grow crops without soil
Deliberately integrates trees and shrubs with crops and/or livestock to create ecological and economic benefits (Correct answer)
Restricts farming to naturally forested areas without clearing trees

Correct answer: Deliberately integrates trees and shrubs with crops and/or livestock to create ecological and economic benefits

Agroforestry intentionally combines perennial woody plants with crops and/or animals to exploit synergies: nitrogen fixation by tree legumes, reduced erosion, diversified income, carbon storage, and microclimate benefits.

Question 65: Which of the following best defines ecological footprint?

The physical area of land that has been directly modified or urbanized by human activity
The total monetary cost of environmental damage caused by a country each year
The carbon emissions per capita of a country normalized for population size
The biologically productive land and water area required to produce the resources a population consumes and absorb its wastes (Correct answer)

Correct answer: The biologically productive land and water area required to produce the resources a population consumes and absorb its wastes

The ecological footprint (Wackernagel and Rees, 1996) measures human demand on the biosphere in global hectares, comparing it to Earth's biological capacity (biocapacity) to regenerate resources and absorb wastes.

Question 66: The term 'radiative forcing' refers to:

The change in energy flux in the atmosphere due to a climate driver (Correct answer)
Infrared radiation emitted by greenhouse gases
The reflection of solar radiation by clouds
The amount of solar radiation reaching Earth's surface

Correct answer: The change in energy flux in the atmosphere due to a climate driver

Radiative forcing quantifies how much a climate factor (e.g., CO₂ increase) alters the energy balance of Earth's atmosphere.

Question 67: Which term describes a species native and restricted to a particular geographic area?

Exotic
Migratory
Invasive
Endemic (Correct answer)

Correct answer: Endemic

Endemic species are found exclusively in a specific location and evolved in that area.

Question 68: What is desertification?

Degradation of dryland areas due to human activity and drought (Correct answer)
Conversion of wetlands to desert ecosystems
Coastal erosion from sea level rise
The spread of invasive desert plants

Correct answer: Degradation of dryland areas due to human activity and drought

Desertification is the process by which productive land in arid and semi-arid regions degrades into desert due to overgrazing, deforestation, and drought.

Question 69: The concept of safe minimum standard (SMS) in biodiversity economics suggests that:

Biodiversity protection budgets should be set at the minimum level needed to prevent political opposition
Environmental agencies should set pollution standards at the minimum level the law requires
Society should protect a minimum viable population of all species unless the costs are intolerably high, regardless of cost-benefit calculations (Correct answer)
The safe harbor provisions of the ESA establish a minimum standard for private landowner conservation

Correct answer: Society should protect a minimum viable population of all species unless the costs are intolerably high, regardless of cost-benefit calculations

SMS (Ciriacy-Wantrup) argues that because species extinction is irreversible and the value of biodiversity is highly uncertain, society should maintain a minimum viable population of each species unless costs are catastrophically high.

Question 70: Which ecological concept describes the variety of species in a given area?

Biomass
Bioaccumulation
Biotic potential
Biodiversity (Correct answer)

Correct answer: Biodiversity

Biodiversity refers to the variety and variability of life forms in a specific habitat or region.

Question 71: Which layer of the atmosphere contains the ozone layer that protects Earth from UV radiation?

Stratosphere (Correct answer)
Mesosphere
Thermosphere
Troposphere

Correct answer: Stratosphere

The stratospheric ozone layer (15–35 km altitude) absorbs harmful UV-B and UV-C radiation from the sun.

Question 72: Which of the following is an example of a full cost accounting approach in environmental management?

Calculating the full cost of environmental permits including application and compliance fees
Reporting all financial transactions related to environmental remediation projects
Auditing a company's environmental management system for ISO 14001 compliance
Including environmental externalities and social costs in the price of products (e.g., carbon-inclusive electricity pricing) (Correct answer)

Correct answer: Including environmental externalities and social costs in the price of products (e.g., carbon-inclusive electricity pricing)

Full cost accounting (FCA) incorporates all costs - including environmental externalities, social costs, and lifecycle costs - into product prices or decision-making, rather than externalizing them to society.

Question 73: The triple bottom line (TBL) framework in corporate sustainability reporting measures performance across:

Profit (financial), people (social), and planet (environmental) dimensions (Correct answer)
Economic growth, resource efficiency, and waste reduction targets
Short-term, medium-term, and long-term financial returns on sustainability investments
Local, national, and international environmental regulatory compliance

Correct answer: Profit (financial), people (social), and planet (environmental) dimensions

John Elkington's TBL framework (1994) holds that companies should account for social equity (people) and environmental stewardship (planet) alongside financial profit, recognizing all three as measures of business success.

Question 74: Particulate matter (PM2.5) is especially dangerous to human health because:

Its small size allows it to penetrate deep into the lungs and enter the bloodstream, causing respiratory and cardiovascular disease (Correct answer)
It reacts with atmospheric ozone to form more toxic compounds before entering the lungs
It blocks UV radiation, leading to vitamin D deficiency in exposed populations
PM2.5 carries heavy metals that dissolve in lung fluid and cause kidney damage

Correct answer: Its small size allows it to penetrate deep into the lungs and enter the bloodstream, causing respiratory and cardiovascular disease

Particles 2.5 micrometers or smaller can penetrate to the alveoli, enter the bloodstream, and trigger systemic inflammation linked to cardiovascular disease, stroke, and premature death.

Question 75: What is net primary productivity (NPP)?

Energy consumed by herbivores
Total photosynthesis minus plant respiration (Correct answer)
Total energy in sunlight hitting an area
Total decomposer activity

Correct answer: Total photosynthesis minus plant respiration

NPP is gross primary productivity minus the energy plants use for their own respiration, representing available organic matter.

Question 76: Which sector is the largest source of greenhouse gas emissions in the United States?

Agriculture
Electricity production
Industry
Transportation (Correct answer)

Correct answer: Transportation

Transportation overtook electricity as the largest U.S. GHG source, accounting for about 28% of total emissions.

Question 77: The Kyoto Protocol differed from the Paris Agreement primarily in that:

Paris established binding emission limits; Kyoto only set voluntary pledges
Kyoto addressed ozone depletion; Paris focused on biodiversity
Kyoto covered only developed (Annex I) countries with binding targets; Paris requires all nations to submit nationally determined contributions (Correct answer)
Paris was negotiated under the UN; Kyoto was a bilateral U.S.-China agreement

Correct answer: Kyoto covered only developed (Annex I) countries with binding targets; Paris requires all nations to submit nationally determined contributions

Kyoto (1997) set legally binding emission reduction targets for developed nations only; Paris (2015) includes all parties but uses nationally determined contributions (NDCs) that are not legally binding targets.

Question 78: Which U.S. law provides the primary legal framework for protecting threatened and endangered species and their habitats?

Lacey Act
Endangered Species Act (ESA) (Correct answer)
National Wildlife Refuge Act
Marine Mammal Protection Act

Correct answer: Endangered Species Act (ESA)

The Endangered Species Act (1973) prohibits harm to listed species and requires recovery plans and critical habitat designation.

Question 79: The Ogallala Aquifer, which underlies the U.S. Great Plains, is a critical concern for agriculture because:

It is being depleted by irrigation much faster than it is naturally recharged (Correct answer)
It supplies drinking water to New York City and other major eastern cities
It contains high levels of arsenic that contaminate irrigated crops
It is shrinking due to climate change reducing recharge from glacial melt

Correct answer: It is being depleted by irrigation much faster than it is naturally recharged

The Ogallala is a fossil aquifer recharged over thousands of years; current irrigation withdrawals vastly exceed recharge rates, threatening the agricultural productivity of 8 Great Plains states.

Question 80: A negative externality in economics occurs when:

A company receives a negative return on its environmental investments
A transaction between two parties imposes costs on a third party who is not compensated (Correct answer)
Government regulation reduces the profit margin of a business below zero
Consumers choose not to purchase a product because of its environmental impact

Correct answer: A transaction between two parties imposes costs on a third party who is not compensated

Negative externalities (e.g., pollution) are costs imposed on society that are not reflected in market prices, causing overproduction of harmful activities relative to the social optimum.

Question 81: Which dam removal trend is driven primarily by what environmental concern?

Decreasing sedimentation in reservoirs
Restoring fish migration routes and natural river flow (Correct answer)
Reducing flood risk downstream
Lowering water temperatures

Correct answer: Restoring fish migration routes and natural river flow

Many dams are being removed to allow migratory fish like salmon to access historic spawning grounds and restore natural river ecosystems.

AP Environmental Science Exam

The AP Environmental Science exam assesses students' understanding of environmental concepts, natural systems, and human impacts on the environment, testing scientific principles, analysis, and problem-solving through multiple-choice questions covering 9 content units.

Questions

90 min

Time Limit

65%

To Pass

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