• 76 questions

AP Environmental Science Unit 9 Practice Test

Unofficial practice for Unit 9 of AP Environmental Science, Global Change: ozone, greenhouse gases, climate, oceans and biodiversity.

Where is most of the ozone in Earth's atmosphere found?

Pick an answer, then press Check answer. Then you see Correct or Not quite, with the reason. Keys: A to D pick, Enter checks.

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Unofficial practice questions, not affiliated with the College Board. Bank checked October 14, 2026.

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All 76 questions

Topic 9.1: Stratospheric ozone depletion 9

  • About how many ozone molecules can one chlorine atom destroy before it leaves the stratosphere? U.S. Environmental Protection Agency, "Basic Ozone Layer Science"; course topic 9.1
  • During the yearly ozone hole over Antarctica, what can happen to the UVB measured at the surface there? U.S. Environmental Protection Agency, "Health and Environmental Effects of Ozone Layer Depletion"; course topic 9.1
  • How many oxygen atoms does a molecule of ozone contain? U.S. Environmental Protection Agency, "Basic Ozone Layer Science"; course topic 9.1
  • What is the Antarctic ozone "hole"? U.S. Environmental Protection Agency, "Basic Ozone Layer Science"; course topic 9.1
  • Where is most of the ozone in Earth's atmosphere found? U.S. Environmental Protection Agency, "Basic Ozone Layer Science"; course topic 9.1
  • Which band of ultraviolet radiation is not absorbed by ozone? U.S. Environmental Protection Agency, "Basic Ozone Layer Science"; course topic 9.1
  • Which human-made chemicals does the course outline name as a cause of stratospheric ozone depletion? College Board, AP Environmental Science Course and Exam Description, topic 9.1, essential knowledge STB-4.A.2
  • Which natural factor does the course outline name as a cause of stratospheric ozone depletion? College Board, AP Environmental Science Course and Exam Description, topic 9.1, essential knowledge STB-4.A.2
  • Which two effects on people does the course outline link to greater exposure to UV rays? College Board, AP Environmental Science Course and Exam Description, topic 9.1, essential knowledge STB-4.A.3
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Topic 9.2: Reducing ozone depletion 5

  • Because of measures taken under the Montreal Protocol, when is the ozone layer expected to be fully healed? U.S. Environmental Protection Agency, "International Treaties and Cooperation about the Protection of the Stratospheric Ozone Layer"; course topic 9.2
  • Under the terms the parties set in 1992, by what year were developed countries to end production of CFCs? U.S. Environmental Protection Agency, "International Treaties and Cooperation about the Protection of the Stratospheric Ozone Layer"; course topic 9.2
  • What does the adjustment provision of the Montreal Protocol let its parties do? U.S. Environmental Protection Agency, "International Treaties and Cooperation about the Protection of the Stratospheric Ozone Layer"; course topic 9.2
  • Which 1985 agreement first formalized international cooperation on the ozone layer, without requiring concrete controls? U.S. Environmental Protection Agency, "International Treaties and Cooperation about the Protection of the Stratospheric Ozone Layer"; course topic 9.2
  • Which chemicals does the course outline name as a replacement for CFCs? College Board, AP Environmental Science Course and Exam Description, topic 9.2, essential knowledge STB-4.B.1

Topic 9.3: The greenhouse effect 9

  • A gas's global warming potential depends on how long it stays in the atmosphere and on what else? U.S. Environmental Protection Agency, "Understanding Global Warming Potentials"; course topic 9.3
  • About how long does methane emitted today last in the atmosphere, on average? U.S. Environmental Protection Agency, "Understanding Global Warming Potentials"; course topic 9.3
  • According to the course outline, why does water vapor not contribute significantly to global climate change? College Board, AP Environmental Science Course and Exam Description, topic 9.3, essential knowledge STB-4.C.2
  • Nitrous oxide has a 100-year global warming potential of 273. A farm emits 2 tons of nitrous oxide. How many tons of carbon dioxide would cause the same warming over 100 years? U.S. Environmental Protection Agency, "Understanding Global Warming Potentials"; course topic 9.3
  • What does the greenhouse effect do for Earth, according to the course outline? College Board, AP Environmental Science Course and Exam Description, topic 9.3, essential knowledge STB-4.C.3
  • What time period is usually used when a global warming potential is stated? U.S. Environmental Protection Agency, "Understanding Global Warming Potentials"; course topic 9.3
  • Which gas has a global warming potential of 1 and is the reference point for the others? College Board, AP Environmental Science Course and Exam Description, topic 9.3, essential knowledge STB-4.D.1
  • Which list holds only gases that the course outline names as principal greenhouse gases? College Board, AP Environmental Science Course and Exam Description, topic 9.3, essential knowledge STB-4.C.1
  • Which order runs from the highest global warming potential to the lowest, according to the course outline? College Board, AP Environmental Science Course and Exam Description, topic 9.3, essential knowledge STB-4.D.1

Topic 9.4: Increases in the greenhouse gases 7

  • A station records 350 parts per million of carbon dioxide in one year and 420 parts per million years later. What is the percent increase? College Board, AP Environmental Science Course and Exam Description, topic 9.4, essential knowledge STB-4.E.1
  • A tide gauge shows sea level rising at a steady 4 millimeters per year. At that rate, how much would it rise in 50 years? College Board, AP Environmental Science Course and Exam Description, topic 9.4, essential knowledge STB-4.E.1
  • According to the course outline, in which direction are disease vectors spreading as the climate warms? College Board, AP Environmental Science Course and Exam Description, topic 9.4, essential knowledge STB-4.E.1
  • The course outline says rising seas and spreading disease vectors can lead to which response? College Board, AP Environmental Science Course and Exam Description, topic 9.4, essential knowledge STB-4.E.1
  • Greenhouse gas concentrations are measured in parts per million. One part per million is like one drop of water in about how much liquid? U.S. Environmental Protection Agency, "Overview of Greenhouse Gases"; course topic 9.4
  • Greenhouse gases stay in the atmosphere long enough to become well mixed. What does that mean? U.S. Environmental Protection Agency, "Overview of Greenhouse Gases"; course topic 9.4
  • Which is a source of methane emissions named by the EPA? U.S. Environmental Protection Agency, "Overview of Greenhouse Gases"; course topic 9.4

Topic 9.5: Global climate change 12

  • About how long does a parcel of water take to complete the journey along the global ocean conveyor belt? NOAA National Ocean Service, Currents tutorial, "The Global Conveyor Belt"; course topic 9.5
  • According to the course outline, why does the loss of polar ice and snow threaten some species? College Board, AP Environmental Science Course and Exam Description, topic 9.5, essential knowledge STB-4.F.10
  • How can a rise in sea level help some marine ecosystems, according to the course outline? College Board, AP Environmental Science Course and Exam Description, topic 9.5, essential knowledge STB-4.F.3
  • How can climate change affect soil, according to the course outline? College Board, AP Environmental Science Course and Exam Description, topic 9.5, essential knowledge STB-4.F.6
  • Melting ice exposes a darker surface, which absorbs more solar energy and causes more warming and more melting. What kind of loop is this? College Board, AP Environmental Science Course and Exam Description, topic 9.5, essential knowledge STB-4.F.7 and STB-4.F.8
  • What does the course outline say ocean currents, or the ocean conveyor belt, carry throughout the world? College Board, AP Environmental Science Course and Exam Description, topic 9.5, essential knowledge STB-4.F.5
  • Which features of atmospheric circulation does the course outline say a changing climate may affect? College Board, AP Environmental Science Course and Exam Description, topic 9.5, essential knowledge STB-4.F.4
  • Which greenhouse gas does the course outline name as released when Arctic tundra thaws? College Board, AP Environmental Science Course and Exam Description, topic 9.5, essential knowledge STB-4.F.9
  • Which is an effect of climate change listed in the course outline? College Board, AP Environmental Science Course and Exam Description, topic 9.5, essential knowledge STB-4.F.2
  • Which records does the course outline name as evidence of Earth's past periods of warming and cooling? College Board, AP Environmental Science Course and Exam Description, topic 9.5, essential knowledge STB-4.F.1
  • Why can a rise in sea level harm deeper marine communities, according to the course outline? College Board, AP Environmental Science Course and Exam Description, topic 9.5, essential knowledge STB-4.F.3
  • Why does surface water sink near the pole in the North Atlantic, starting the global conveyor belt? NOAA National Ocean Service, Currents tutorial, "The Global Conveyor Belt"; course topic 9.5

Topic 9.6: Ocean warming 6

  • In the bleaching event of 2005, what share of its Caribbean coral reefs did the United States lose in one year? NOAA National Ocean Service, "What is coral bleaching?"; course topic 9.6
  • Is a coral dead once it has bleached? NOAA National Ocean Service, "What is coral bleaching?"; course topic 9.6
  • What are zooxanthellae? NOAA National Ocean Service, "What is coral bleaching?"; course topic 9.6
  • What caused the coral bleaching event in the Florida Keys in January 2010? NOAA National Ocean Service, "What is coral bleaching?"; course topic 9.6
  • What causes ocean warming, according to the course outline? College Board, AP Environmental Science Course and Exam Description, topic 9.6, essential knowledge STB-4.G.1; NOAA National Ocean Service, "Is sea level rising?"
  • Which effects of ocean warming on marine species does the course outline list? College Board, AP Environmental Science Course and Exam Description, topic 9.6, essential knowledge STB-4.G.2

Topic 9.7: Ocean acidification 7

  • About what share of the carbon dioxide released into the atmosphere does the ocean absorb? NOAA National Ocean Service, "What is ocean acidification?"; course topic 9.7
  • According to the course outline, the loss of which compound makes it hard for corals to form shells in a more acidic ocean? College Board, AP Environmental Science Course and Exam Description, topic 9.7, essential knowledge STB-4.H.4
  • How can more acidic water affect certain fish, according to NOAA? NOAA National Ocean Service, "What is ocean acidification?"; course topic 9.7
  • Ocean acidification is a decrease in which property of seawater? College Board, AP Environmental Science Course and Exam Description, topic 9.7, essential knowledge STB-4.H.1
  • When seawater absorbs carbon dioxide, which ion becomes more concentrated? NOAA National Ocean Service, "What is ocean acidification?"; course topic 9.7
  • Which human activities does the course outline list as contributing to ocean acidification? College Board, AP Environmental Science Course and Exam Description, topic 9.7, essential knowledge STB-4.H.3
  • Which ion, a building block of sea shells and coral skeletons, becomes less abundant as the ocean absorbs carbon dioxide? NOAA National Ocean Service, "What is ocean acidification?"; course topic 9.7

Topic 9.8: Invasive species 6

  • According to the course outline, when is a species that lives outside its normal habitat considered invasive? College Board, AP Environmental Science Course and Exam Description, topic 9.8, essential knowledge EIN-4.A.1
  • How do experts think lionfish reached the Atlantic Ocean? NOAA National Ocean Service, "What is a lionfish?"; course topic 9.8
  • Lionfish are invasive along the southeast coast of the United States. Where are they native? NOAA National Ocean Service, "What is a lionfish?"; course topic 9.8
  • What advantage do lionfish have in Atlantic waters, according to NOAA? NOAA National Ocean Service, "What is a lionfish?"; course topic 9.8
  • What have NOAA researchers concluded about removing invasive lionfish? NOAA National Ocean Service, "What is a lionfish?"; course topic 9.8
  • Which description fits most invasive species, according to the course outline? College Board, AP Environmental Science Course and Exam Description, topic 9.8, essential knowledge EIN-4.A.2

Topic 9.9: Endangered species 7

  • According to the course outline, which species are less likely to face extinction when their ecosystem changes? College Board, AP Environmental Science Course and Exam Description, topic 9.9, essential knowledge EIN-4.B.2
  • Under the Endangered Species Act, which actions against a listed animal count as a "take"? NOAA Fisheries, "Endangered Species Act", section 3; course topic 9.9
  • What does the course outline call any factors that change the behaviors and fitness of organisms within an environment? College Board, AP Environmental Science Course and Exam Description, topic 9.9, essential knowledge EIN-4.B.3
  • Which international convention does the Endangered Species Act of the United States implement? U.S. Fish and Wildlife Service, "Endangered Species Act"; course topic 9.9
  • Which resources does the course outline say species in an ecosystem compete for? College Board, AP Environmental Science Course and Exam Description, topic 9.9, essential knowledge EIN-4.B.4
  • Which strategies to protect animal populations does the course outline list? College Board, AP Environmental Science Course and Exam Description, topic 9.9, essential knowledge EIN-4.B.5
  • Which trait makes a species more likely to become threatened with extinction, according to the course outline? College Board, AP Environmental Science Course and Exam Description, topic 9.9, essential knowledge EIN-4.B.1

Topic 9.10: Human impacts on biodiversity 8

  • A strip of protected forest links two wildlife reserves so that animals can move between them. Which strategy from the course outline is this? College Board, AP Environmental Science Course and Exam Description, topic 9.10, essential knowledge EIN-4.C.6
  • According to the course outline, how does the scale of fragmentation that harms an ecosystem's inhabitants compare from one species to another? College Board, AP Environmental Science Course and Exam Description, topic 9.10, essential knowledge EIN-4.C.3
  • In HIPPCO, the main factors behind a decrease in biodiversity, what does the O stand for? College Board, AP Environmental Science Course and Exam Description, topic 9.10, essential knowledge EIN-4.C.1
  • In HIPPCO, what do the two letters P stand for? College Board, AP Environmental Science Course and Exam Description, topic 9.10, essential knowledge EIN-4.C.1
  • Through which changes can global climate change cause habitat loss, according to the course outline? College Board, AP Environmental Science Course and Exam Description, topic 9.10, essential knowledge EIN-4.C.4
  • What is habitat fragmentation? College Board, AP Environmental Science Course and Exam Description, topic 9.10, essential knowledge EIN-4.C.2
  • Which examples of domesticated organisms managed for economic returns does the course outline give? College Board, AP Environmental Science Course and Exam Description, topic 9.10, essential knowledge EIN-4.C.5
  • Which is a cause of habitat fragmentation listed in the course outline? College Board, AP Environmental Science Course and Exam Description, topic 9.10, essential knowledge EIN-4.C.2 and EIN-4.C.6

How this list was compiled: Our own questions, written to Unit 9 (Global Change, topics 9.1 to 9.10) of the College Board's AP Environmental Science Course and Exam Description, effective fall 2026, https://apcentral.collegeboard.org/media/pdf/ap-environmental-science-course-and-exam-description.pdf, read 2026-10-14. Each fact was read on 2026-10-14 in the public page named under its question: an essential knowledge statement of the course description; a page of the U.S. Environmental Protection Agency, the NOAA National Ocean Service, NOAA Fisheries or the U.S. Fish and Wildlife Service. Answers that are worked out were recomputed. Licence: Own work.

How it works

This AP Environmental Science Unit 9 practice test has 76 questions of our own on Global Change. It is unofficial and not affiliated with the College Board, which owns AP.

Read the full guide

What Unit 9 covers

The College Board's course description, read October 14, 2026, gives Unit 9 ten topics, and each has a set here: stratospheric ozone depletion (9 questions), reducing ozone depletion (5), the greenhouse effect (9), increases in the greenhouse gases (7), global climate change (12), ocean warming (6), ocean acidification (7), invasive species (6), endangered species (7) and human impacts on biodiversity (8). The description weights no topic, so the spread is ours.

Sources you can open

Each answer cites a statement of the course description or a page of the EPA, NOAA or the U.S. Fish and Wildlife Service. Three answers are arithmetic. The questions on ultraviolet rays and health repeat the outline only: practice for an exam, not medical advice.

  • Sort each question first: ozone depletion is about ultraviolet rays reaching the surface, the greenhouse effect about heat held near it.
  • For carbon dioxide equivalent, multiply the mass of the gas by its global warming potential.

Questions and answers

What is Unit 9 in AP Environmental Science?

Global Change, the last of nine units. Its ten topics run from stratospheric ozone depletion (9.1) through the greenhouse effect, climate change, ocean warming and ocean acidification to invasive species, endangered species and human impacts on biodiversity (9.10).

How much of the APES exam is Unit 9?

From 15 to 20% of the multiple-choice section, by the College Board's course page. No unit carries a higher weighting. The course description suggests about 19 to 20 class periods for it.

What does HIPPCO stand for?

Habitat destruction, invasive species, population growth, pollution, climate change and over exploitation. The course description gives these as the main factors leading to a decrease in biodiversity.

What is the difference between ocean warming and ocean acidification?

Ocean warming is caused by the increase in greenhouse gases in the atmosphere and leads to coral bleaching. Ocean acidification is a decrease in the pH of the oceans as they absorb carbon dioxide, which costs corals calcium carbonate.

Is this the College Board's Unit 9 progress check?

No. Its Progress Check for Unit 9, about 25 multiple-choice questions and one free-response question by the course description, is assigned in AP Classroom. The 76 questions here were written for this page and copy none of it.

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