AP Environmental Science Unit 9: Global Change Practice Exam

1. [Skill: 4A | Topic: 9.1] A research team measures average midday UV-B radiation at Earth’s surface on days with different total stratospheric ozone amounts. The results are summarized below. Ozone (Dobson units): 340, 320, 300, 280 UV-B at surface (relative units): 1.0, 1.2, 1.5, 1.9 Which of the following best explains why the stratospheric ozone layer is important to life on Earth?

2. [Skill: 1A | Topic: 9.1] A textbook passage states: “Chlorofluorocarbons (CFCs) are chemically stable in the lower atmosphere. Over time they drift into the stratosphere, where high-energy ultraviolet radiation causes them to break apart and release chlorine atoms. The chlorine atoms participate in reactions that convert ozone ($O_3$) into oxygen ($O_2$) and can repeat the process many times.” Which of the following best identifies the anthropogenic factor described and explains how it contributes to stratospheric ozone depletion?

3. [Skill: 6A | Topic: 9.1] A coastal city reports a long-term increase in summertime cases of cataracts and a rise in sunburn severity among residents. Atmospheric monitoring also indicates episodic thinning of the stratospheric ozone layer during spring. Which policy would most directly address the health impacts described by targeting the primary cause of stratospheric ozone depletion?

4. [Skill: 2A | Topic: 9.10] A biologist surveys a mountain ecosystem and records the following over 25 years: - Mean spring temperature increased by 2.1°C. - Average spring snowpack depth decreased by 35%. - A cold-adapted pika population declined from 120 individuals to 25 individuals. - Vegetation maps show the area of alpine meadow habitat shrinking and shifting upslope. Which of the following best identifies the major HIPPCO factor causing the population decline and explains the mechanism? [Image Cue]: Line graph, "Spring Climate Trends in Alpine Habitat (1999–2024)", x-axis: Year (1999–2024), left y-axis: Mean spring temperature (°C), right y-axis: Snowpack depth (cm), key trend: temperature increases steadily while snowpack decreases steadily.

5. [Skill: 4A | Topic: 9.10] A region of temperate forest is converted into a patchwork of small forest fragments due to construction of a highway and new agricultural fields. Ecologists compare two bird species: - Species X nests only in forest interior (requires large, continuous habitat). - Species Y can nest on forest edges and in small patches. After fragmentation, surveys show that Species X declines sharply while Species Y remains stable. Which of the following best explains the decline of Species X and identifies a mitigation strategy most likely to improve its long-term survival in the region? [Image Cue]: Map diagram, "Forest Fragmentation and Highway", showing a once-continuous forest split into 6 isolated patches by a highway and fields; arrows indicating limited movement between patches; edge habitat surrounding each patch is emphasized.

6. [Skill: 1A | Topic: 9.10] A company replaces multiple locally adapted varieties of wheat with a single high-yield domesticated strain across a large farming region. After several years, a fungal disease outbreak occurs. Data from genetic testing are shown below. Genetic diversity (number of alleles detected at key resistance loci): - Wild wheat relatives: 18 alleles - Traditional local varieties (before replacement): 12 alleles - High-yield domesticated strain: 3 alleles Which of the following best explains how domestication can negatively impact biodiversity and why the new planting strategy increases risk from disease?

7. [Skill: 2.B | Topic: 9.2] A student examines a figure comparing the ozone depletion potential (ODP) and 100-year global warming potential (GWP) of several refrigerants. [Image Cue]: Scatter plot, "ODP vs. GWP for Common Refrigerants," x-axis = ODP (0 to 1.2), y-axis = 100-year GWP (0 to 12000). Points labeled: CFC-12 at (1.0, ~10900), HCFC-22 at (~0.05, ~1800), HFC-134a at (0, ~1430), and CO2 at (0, 1). Trend: CFC-12 has high ODP and high GWP; HCFC-22 lower ODP but still >0; HFC-134a ODP = 0 but high GWP; CO2 baseline low. Which chemical shown is an example of a substitute for CFCs that does not deplete the ozone layer but can still contribute significantly to global warming?

8. [Skill: 1.A | Topic: 9.2] A manufacturer replaces CFC-based foam-blowing agents with hydrofluorocarbons (HFCs). After the switch, the company reports that it has eliminated its direct contribution to stratospheric ozone depletion. Which of the following best explains why using HFCs instead of CFCs helps mitigate ozone depletion?

9. [Skill: 4.A | Topic: 9.2] A student compares several potential replacements for CFCs. The table below lists whether each chemical depletes ozone and provides its 100-year global warming potential (GWP). [Image Cue]: Table, "Properties of Candidate CFC Replacements," columns: Chemical; Ozone-depleting? (Yes/No); 100-year GWP. Rows: CFC-11 (Yes, 4660); HCFC-141b (Yes, 725); HFC-134a (No, 1430); HFC-152a (No, 124). Based on the table, which choice best supports the essential knowledge that ozone depletion can be mitigated by replacing CFCs with substitutes that do not deplete ozone, but that some substitutes are strong greenhouse gases?

10. [Skill: 1A | Topic: 9.3] A student reads the following statement in a climate report: “Several atmospheric gases absorb outgoing infrared radiation and re-radiate heat back toward Earth’s surface, contributing to warming.” Which of the following sets contains only the principal greenhouse gases?

11. [Skill: 4A | Topic: 9.3] Scientists compare Earth’s average surface temperature under two modeled conditions: Model 1: Earth with no greenhouse gases in the atmosphere. Model 2: Earth with its natural greenhouse gas concentrations. The models predict that Model 1 would have a much lower average surface temperature than Model 2. Which of the following best explains why the greenhouse effect is essential for life on Earth to exist?

12. [Skill: 1A | Topic: 9.3] A policy team is prioritizing emissions reductions based on each gas’s global warming potential (GWP), using $CO_2$ as the reference point (GWP = 1). Based on the relative GWP described in the unit, which greenhouse gas has the highest GWP?

13. **1.** [Skill: 4.A | Topic: 9.4] A research team summarizes observed global mean sea level rise (GMSL) and estimated contributions over two recent decades. [Image Cue]: Stacked bar graph, "Estimated Contributions to Global Mean Sea Level Rise," x-axis = time period (1993–2002, 2013–2022), y-axis = sea level contribution (mm). Each bar is stacked with segments labeled "Thermal expansion" and "Land ice melt (glaciers + ice sheets)." Key trends: total height increases from first to second decade; both segments increase, with land ice melt showing the larger increase. Based on the graph, which of the following identifies the two primary mechanisms responsible for the observed increase in global mean sea level in a warming climate?

14. **2.** [Skill: 2.A | Topic: 9.4] A public health agency models the potential range of a mosquito species that can transmit dengue fever under two climate conditions. [Image Cue]: Map pair, "Projected Mosquito Habitat Suitability." Map 1 (Present) shows high suitability mostly from 30°S to 30°N. Map 2 (Warming scenario) shows suitability expanding toward higher latitudes in both hemispheres (e.g., up to ~40–45°). Legend indicates low to high suitability. Which of the following best explains the most likely reason the modeled disease vector range expands toward the poles under the warming scenario?

15. **3.** [Skill: 6.B | Topic: 9.4] A coastal nation releases the following summary from a national climate assessment: - “Tide-gauge records show the rate of sea level rise has increased in recent decades.” - “The country’s most densely populated region is a low-lying delta, where many communities rely on shallow groundwater.” - “Public health officials have documented an increase in locally acquired cases of mosquito-borne illness in areas that historically experienced winters cold enough to limit mosquito survival.” Which of the following statements best connects increased greenhouse gas concentrations to the environmental and human-health threats described, including likely effects on population dynamics?

16. [Skill: 4.A | Topic: 9.5] [Image Cue]: Line graph, "Ice Core Record of Atmospheric $CO_2$ and Temperature (Past 400,000 Years)". X-axis: "Years before present" from 400,000 to 0. Left Y-axis: "Atmospheric $CO_2$ (ppm)" ranging approximately 180–300. Right Y-axis: "Temperature anomaly (°C)" ranging approximately -8 to +2. The graph shows repeated glacial-interglacial cycles where $CO_2$ peaks (~280–300 ppm) align with warmer temperature anomalies and $CO_2$ troughs (~180–200 ppm) align with colder anomalies. A student claims that Earth’s climate has remained stable over geologic time and that $CO_2$ levels do not vary naturally. Based on the ice core record shown, which of the following statements is best supported by the data?

17. [Skill: 1.B | Topic: 9.5] Researchers monitoring the Arctic observe that summer sea-ice extent has decreased over several decades. In the same region, some tundra areas that were previously frozen year-round are thawing for longer periods each summer. The researchers note that these changes can affect the rate of warming in the Arctic compared with lower latitudes. Which of the following best explains why Earth’s polar regions can show faster response times to global climate change?

18. **1. [Skill: SP3 (Data Analysis) | Topic: 9.6]** A climate scientist compares long-term atmospheric carbon dioxide concentrations with a measure of ocean warming. [Image Cue]: Dual-axis line graph, "Atmospheric CO2 and Global Ocean Heat Content (1950–2020)". X-axis: Year (1950–2020). Left Y-axis: Atmospheric CO2 (ppm), increasing from ~310 to ~415. Right Y-axis: Ocean heat content (relative units), increasing gradually with faster rise after ~1980. Both lines trend upward; CO2 rises steadily, ocean heat content rises with a lag. Which of the following best explains the most likely causal chain linking the two trends shown in the graph?

19. **2. [Skill: SP1 (Concept Explanation) | Topic: 9.6]** Marine biologists monitored a shallow coral reef during a marine heat wave. For two weeks, average sea-surface temperature at the site was 2°C above the long-term summer maximum. By the end of the heat wave, many corals had turned visibly white, and algal cell counts within coral tissues were much lower than counts measured before the heat wave. Which of the following best explains the whitening observed and a likely ecological consequence if high temperatures persist?

20. [Skill: 2A | Topic: 9.7] A research team measured atmospheric carbon dioxide concentration and surface ocean pH in the North Atlantic from 1960 to 2020. [Image Cue]: Line graph, "Atmospheric CO2 and Surface Ocean pH (1960–2020)". X-axis: Year (1960, 1980, 2000, 2020). Left Y-axis: Atmospheric CO2 (ppm) increasing from about 315 (1960) to about 415 (2020). Right Y-axis: Surface ocean pH decreasing from about 8.15 (1960) to about 8.05 (2020). Key trend: as CO2 rises, pH declines. Which of the following best explains the observed decline in ocean pH and a likely biological consequence?

21. [Skill: 1A | Topic: 9.7] A student models the primary reactions involved when excess atmospheric $CO_2$ dissolves in seawater: 1) $CO_2(g) \rightleftharpoons CO_2(aq)$ 2) $CO_2(aq) + H_2O \rightleftharpoons H_2CO_3$ 3) $H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$ 4) $H^+ + CO_3^{2-} \rightleftharpoons HCO_3^-$ Which of the following anthropogenic activities most directly increases the reactant that drives these reactions and leads to decreased availability of $CO_3^{2-}$ for shell formation?

22. [Skill: 4.A | Topic: 9.8] A coastal island has recently recorded the establishment of a non-native rat species. Ecologists collected the following information during the first two years after introduction. Table 1. Comparison of invasive rat and a native rodent species - Average offspring per female per year: Invasive rat = 24; Native rodent = 6 - Age at first reproduction: Invasive rat = 3 months; Native rodent = 12 months - Diet breadth (number of major food categories consumed): Invasive rat = 6; Native rodent = 2 - Number of known predators on the island: Invasive rat = 0; Native rodent = 3 Which of the following best explains why the introduced rat is likely to become invasive on the island?

23. [Skill: 2.B | Topic: 9.8] A freshwater lake has been invaded by a non-native floating plant that forms dense surface mats, reducing light penetration and decreasing dissolved oxygen (DO). Managers tested three interventions in similar coves of the lake. [Image Cue]: Line graph, "Invasive Plant Surface Cover Over Time Under Different Controls". X-axis: Time (weeks 0 to 12). Y-axis: Plant cover (% of water surface, 0 to 100). Three lines: (1) No intervention stays ~80–90% throughout. (2) Mechanical removal drops from ~85% to ~30% at week 2, then gradually rises to ~60% by week 12. (3) Biological control agent release drops from ~85% to ~70% by week 4, then steadily declines to ~25% by week 12. Based on the graph and the goal of long-term reduction of the invasive plant, which strategy is best supported, and why?

24. [Skill: 4A | Topic: 9.9] [Image Cue]: Line graph, "Population Size of Island Ground-Nesting Bird (2008–2020)", x-axis = Year (2008–2020), y-axis = Estimated population (individuals). Trend: population is ~1,200 and stable from 2008–2011; an invasive snake is first documented in 2012; population declines to ~300 by 2016 and ~120 by 2020. A note on the graph indicates annual rainfall and available nesting habitat area remained approximately constant over the entire period. A conservation biologist is investigating why a ground-nesting bird population on an island rapidly declined after 2012. Based on the graph, which of the following is the most likely selective pressure contributing to the decline?

25. [Skill: 6A | Topic: 9.9] A threatened mammal species lives only in a narrow band of coastal marsh. The species has a highly specialized diet (it eats one species of marsh snail) and rarely disperses to new areas. In recent years, the marsh has been reduced by shoreline development, and reports of illegal hunting have increased. Which of the following management actions best addresses the primary factors driving this species toward endangerment?