2023 AP Environmental Science Free-Response Questions

ENVIRONMENTAL SCIENCE SECTION II Time—1 hour and 10 minutes 3 Questions Directions: Answer all three questions, which are weighted equally; the suggested time is about 22 minutes for answering each question. Write all your answers in the Free Response booklet. Where calculations are required, clearly show how you arrived at your answer. Where explanation or discussion is required, support your answers with relevant information and/or specific examples. You may plan your answers in this orange booklet, but no credit will be given for anything written in this booklet. You will only earn credit for what you write in the separate Free Response booklet. 1. Researchers interested in sustainability developed three new varieties of genetically modified green beans designed to produce higher yields in arid regions. Four plots (A–D) were set up on a floodplain of a river to grow beans. Plots A, B, and C were each planted with seeds of different types of genetically modified strains of green beans. Plot D was planted with seeds of unmodified green beans. Each plot was given equal amounts of fertilizer, which contains phosphorus and nitrogen, and water and was irrigated using spray irrigation for one hour per day. Throughout the growing season, researchers measured the amount of green beans harvested within each plot. The plots with genetically modified beans had higher crop yields than the plot with unmodified beans. (a) Identify the control group in this experiment. (b) Identify the scientific question for the investigation. (c) Researchers repeated the experiment by modifying the length of time for the spray irrigation to 20 minutes per day. Explain how the results of the experiment could be altered with this modification. Researchers also monitored the amount of sediment and fertilizer washing into the river from each plot in the original study. The soil temperature was also measured in each plot at the same depth and at the same time each day approximately 0.05 meters below the surface of the soil. Genetically Modified Green Bean Experimental Results Plot | Sediment Runoff (mg/L) | Phosphorus Runoff (mg/L) | Nitrogen Runoff (mg/L) | Soil Temperature (°C) A (Type 1 GMO beans) | 2.4 | 0.11 | 1.07 | 18.6 B (Type 2 GMO beans) | 2.1 | 0.02 | 0.56 | 18.3 C (Type 3 GMO beans) | 0.9 | 0.04 | 0.68 | 18.3 D (Unmodified beans) | 3.5 | 0.15 | 1.24 | 17.6 (d) Based on the data in the table, identify the plot with the lowest soil temperature. (e) Describe how sediment runoff and fertilizer runoff compare between the unmodified green beans and the genetically modified green beans. (f) The Type 2 GMO beans in Plot B were developed to grow more quickly than the unmodified beans in Plot D. Researchers have hypothesized that the Type 2 beans would use fertilizer more completely than the other varieties. Based on the data in the table and the experimental design, explain whether the researchers' hypothesis was supported or refuted. Once the experiment was concluded, the researchers burned the plots to remove the crops that had been planted. After a few years, the researchers returned to the plots and observed a variety of plants, insects, and bird species living there. (g) Describe the ecological process that occurred on the plots after the crops were burned. A survey indicated that one of the plots had twice the plant diversity that the other plots had. Over the next five years, the river occasionally flooded the plots, killing off many of the species that inhabited the plots. (h) After each flooding event, the plot with twice the plant diversity returned to its prior level of biodiversity more quickly than the other plots did. Explain why a community with more plant diversity will recover more quickly from the flooding. (i) After the last flooding event, a beetle not previously known in the area appeared in one of the plots with less plant diversity. Over a period of a few months, the new beetle population increased, whereas the existing beetle species in the plot had declining populations. Explain why the new beetle species could be better able to successfully populate this plot than the existing beetle species could. (j) Describe one realistic method to prevent the new beetle from spreading beyond the experimental plot. Begin your response to this question at the top of a new page in the separate Free Response booklet and fill in the appropriate circle at the top of each page to indicate the question number.

2. The diagram shows the movement of one adult manatee over a 12-hour period across an active shipping channel during the winter. Manatees are large, aquatic, herbivorous mammals that primarily eat seagrass. Manatees can travel several miles to graze. Manatees mature slowly, have low biotic potential, and inhabit warm coastal waters. They cannot survive in water below 20°C for extended periods of time. Satellite Track and Water Temperature Log of the Movement of One Adult Manatee Over a 12-Hour Period Key Urban land Bay water Seagrass beds Water Temperature ○ 13–19°C □ 20–23°C △ 24–26°C (a) Based on the information in the diagram, identify the temperature range of the water through which the majority of the adult manatee's daily movement occurs. (b) Large groups of manatees are often observed in shallow waters near the waste water released by the electrical power plant during the winter. Based on the information in the diagram, identify a characteristic of the power plant waste water that would attract the manatees. (c) Based on the information in the diagram, describe a potential negative impact of the waste water released by the power plant on other aquatic species. (d) Seagrass beds have declined significantly over the last several years. In 2021 manatee mortality was three times higher than the previous five-year average. (i) Describe a characteristic of the manatees that increases their vulnerability to the recent decline of seagrasses. (ii) Describe the change in energy flow through the trophic levels that occurs when there is a significant loss of seagrasses. (e) Research has shown increased nutrient and sediment runoff can cause seagrass beds to decline. (i) Propose a solution to reduce nutrient or sediment pollution in an estuary that is surrounded by urban development. (ii) Justify the solution proposed in part (e)(i) by providing an additional advantage of reduced nutrients in an estuary, other than one related to manatees. Urban areas have a heavy dependence on automobiles and often experience photochemical smog. (f) Describe how summertime weather conditions can increase the frequency of photochemical smog. (g) Identify one ecological problem that results from exposure to photochemical smog. A potential solution to reduce photochemical smog in urban areas with high automobile traffic is to replace gasoline-powered cars with cars powered by hydrogen fuel cells. (h) Describe a potential disadvantage of using hydrogen fuel cells to power automobiles. Begin your response to this question at the top of a new page in the separate Free Response booklet and fill in the appropriate circle at the top of each page to indicate the question number.

3. Crude oil is extracted, transported, and refined for various uses by humans. (a) Describe one environmental impact on marine ecosystems associated with extraction or transportation of crude oil. (b) Identify an atmospheric pollutant released during the combustion of refined oil products. (c) Propose a solution an individual can use to reduce their reliance on refined oil products for transportation. (d) Justify the solution proposed in part (c) by providing a benefit to human health. Other natural resources, such as gold and silver, are also extracted. These resources can be used to make components for the electronics humans use. One metric ton of gold ore contains 5.0 grams of gold. (e) A deposit is estimated to contain 260 million metric tons of gold ore. Calculate the number of grams of gold that could be extracted from the deposit. Show your work. (f) Assuming the price of gold is $62.56 per gram, calculate the value of the gold that could be recovered from 1,000 metric tons of gold ore in the deposit. Show your work. (g) A typical cell phone contains 0.034 grams of gold. Calculate how many metric tons of gold ore would need to be mined to extract enough gold to manufacture 100,000 cell phones. Show your work. Begin your response to this question at the top of a new page in the separate Free Response booklet and fill in the appropriate circle at the top of each page to indicate the question number.