Free AP® Environmental Science Practice Test (2026)

Question 1

Which process is mainly responsible for the thinning of the stratospheric ozone layer?

Accepted Answer

Chlorine atoms released from CFCs by ultraviolet light, which break down ozone in a repeating chain reaction

Answer

Carbon dioxide trapping heat in the stratosphere, which breaks ozone molecules apart

Answer

Sulfur dioxide from coal-fired power plants reacting directly with ozone

Answer

Methane from livestock rising into the stratosphere and absorbing ozone

Question 2

A country's population is growing at 2% per year. Using the rule of 70, about how long will it take the population to double?

Accepted Answer

35 years

Answer

14 years

Answer

20 years

Answer

140 years

Question 3

The producers in a food chain capture 50,000 kcal of energy. Following the 10% rule, about how much of that energy reaches the tertiary consumers?

Accepted Answer

50 kcal

Answer

500 kcal

Answer

5,000 kcal

Answer

5 kcal

Question 4

How does a nuclear fission power plant produce electricity?

Accepted Answer

Heat from splitting uranium-235 nuclei turns water into steam, which spins a turbine connected to a generator.

Answer

Hydrogen nuclei fuse in the reactor core, and the light they give off is turned into electricity.

Answer

The fuel rods give off an electric current directly as the uranium decays.

Answer

The control rods absorb neutrons and convert their energy into electric current.

Question 5

Which set of conditions produces photochemical smog?

Accepted Answer

Nitrogen oxides and volatile organic compounds reacting in sunlight to form ground-level ozone

Answer

Sulfur dioxide and soot from coal burning combining with water droplets on cold, damp winter mornings

Answer

CFCs breaking down the ozone layer directly above a city

Answer

Carbon monoxide combining with dust particles at night

Question 6

A farmer in a dry region wants the irrigation method that delivers the largest share of water to the crop roots with the least lost to evaporation and runoff. Which method should the farmer choose?

Accepted Answer

Drip irrigation

Answer

Furrow irrigation

Answer

Flood irrigation

Answer

Spray irrigation

Question 7

According to the theory of island biogeography, which island would be expected to have the greatest number of species?

Accepted Answer

A large island close to the mainland

Answer

A small island close to the mainland

Answer

A small island far from the mainland

Answer

A large island far from the mainland

Question 8

Fertilizer runoff causes an algal bloom in a lake, and weeks later many fish die. What most directly lowers the dissolved oxygen enough to kill the fish?

Accepted Answer

Bacteria decomposing the dead algae use up dissolved oxygen.

Answer

The algae release toxic levels of carbon dioxide during photosynthesis.

Answer

The nitrates in the runoff poison the fish's gills.

Answer

The phosphates in the runoff bind to oxygen molecules and remove them from the water.

Question 9

Which type of soil has the lowest permeability and the highest water-holding capacity?

Accepted Answer

Clay soil

Answer

Sandy soil

Answer

Gravel

Answer

Loam

Question 10

Over a 100-year period, which of these gases has the highest global warming potential per molecule?

Accepted Answer

Nitrous oxide (N₂O)

Answer

Methane (CH₄)

Answer

Carbon dioxide (CO₂)

Answer

Nitrogen gas (N₂)

Question 11

A 100-watt light bulb is left on 5 hours a day for 30 days. If electricity costs $0.10 per kilowatt-hour, what does it cost to run the bulb for those 30 days?

Accepted Answer

$1.50

Answer

$15.00

Answer

$0.15

Answer

$150.00

Question 12

Oysters release millions of eggs, most of the larvae die soon after hatching, and the few that survive can live for many years. Which survivorship curve fits oysters?

Accepted Answer

Type III: mortality is very high early in life

Answer

Type I: most individuals survive until old age

Answer

Type II: the death rate is about the same at every age

Answer

A logistic curve: mortality rises as the population nears carrying capacity

Question 13

Why does rising atmospheric CO₂ make it harder for corals and shellfish to build their calcium carbonate skeletons and shells?

Accepted Answer

CO₂ dissolves in seawater to form carbonic acid, which lowers the pH and reduces the carbonate ions available to build shells.

Answer

CO₂ raises the pH of seawater, so calcium carbonate cannot form.

Answer

CO₂ blocks the sunlight that corals need to make calcium carbonate.

Answer

CO₂ raises the amount of dissolved oxygen, which dissolves shells.

Question 14

A forested watershed is cleared and paved over for a new suburb with roads, roofs and parking lots. Which change in the watershed is most likely?

Accepted Answer

More surface runoff and less groundwater recharge

Answer

Less surface runoff and more water soaking into the ground

Answer

Lower peak stream flows after heavy storms

Answer

More water returned to the air by evapotranspiration

Question 15

Which process converts nitrogen gas (N₂) from the atmosphere into ammonia that plants can use?

Accepted Answer

Nitrogen fixation

Answer

Denitrification

Answer

Nitrification

Answer

Ammonification

Question 16

What forms where an oceanic plate collides with a continental plate?

Accepted Answer

A deep ocean trench and a chain of volcanic mountains, as the denser oceanic plate subducts

Answer

A mid-ocean ridge where new seafloor is created

Answer

A transform fault where the plates slide past each other without volcanoes

Answer

A rift valley where the continent splits apart

Question 17

A fat-soluble pesticide measures 0.00005 ppm in lake water, more in the zooplankton, more still in small fish, and 25 ppm in fish-eating birds. Which process explains this pattern?

Accepted Answer

Biomagnification

Answer

Bioremediation

Answer

Eutrophication

Answer

Leaching

Question 18

A coal-fired power plant needs to remove fine particulate matter from its exhaust by giving the particles an electric charge and collecting them on oppositely charged plates. Which device does this?

Accepted Answer

An electrostatic precipitator

Answer

A catalytic converter

Answer

A wet scrubber

Answer

A fluidized bed combustor

Question 19

Which combination of traits makes a species most likely to become invasive when it is carried to a new region?

Accepted Answer

A generalist diet, rapid reproduction and few natural predators in the new region

Answer

A narrow diet and slow reproduction

Answer

A specialist diet and a long life with few offspring

Answer

Dependence on a single host plant found only in its native range

Question 20

In which stage of the demographic transition does population grow fastest, because death rates have dropped while birth rates are still high?

Accepted Answer

Stage 2

Answer

Stage 1

Answer

Stage 3

Answer

Stage 4

Question 21

Which fossil fuel releases the least carbon dioxide per unit of energy produced when it is burned?

Accepted Answer

Natural gas

Answer

Anthracite coal

Answer

Lignite coal

Answer

Gasoline

Question 22

In which layer of the atmosphere is the ozone layer found, with temperature rising as altitude increases because ozone absorbs ultraviolet radiation?

Accepted Answer

Stratosphere

Answer

Troposphere

Answer

Mesosphere

Answer

Thermosphere

Question 23

Which practice most directly reduces soil erosion on a farm field that sits on a gentle slope?

Accepted Answer

Contour plowing, with furrows running across the slope

Answer

Plowing furrows straight up and down the slope

Answer

Leaving the field bare between harvests

Answer

Planting the same crop every year with heavy tilling

Question 24

Which of the following is a positive feedback loop that speeds up global warming?

Accepted Answer

Melting sea ice exposes darker ocean water, which absorbs more sunlight and causes more melting.

Answer

Warmer temperatures and more CO₂ increase plant growth, and the plants remove more CO₂ from the air.

Answer

Higher CO₂ levels make the ocean more alkaline, so it absorbs more heat.

Answer

Warmer air holds less water vapor, so the greenhouse effect weakens.

Question 25

If each of the following melted completely, which would contribute least to sea-level rise?

Accepted Answer

Floating Arctic sea ice

Answer

The Greenland ice sheet

Answer

Mountain glaciers

Answer

The ice sheet resting on land in Antarctica

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