2025 AP Environmental Science Free-Response Questions

Chickadees are a K-selected species of bird that eat insects and spiders. Spiders consume insects, and many insects consume plants as shown in the following food chain. Plants → Insects → Spiders Chickadee habitat includes forests and residential yards. Residential yards often contain nonnative plants, which do not naturally exist in an area, but were introduced by humans. Scientists measured the average number of insects and spiders as related to the percentage of nonnative plants (Figure 1). The scientists also measured the chickadees’ average population growth rate (Figure 2) to determine the impact of nonnative plants on chickadee populations. Figure 1. Percentage of Nonnative Plants and Average Number of Individual Spiders and Insects. The graph shows average number of individuals versus nonnative plants (percent), with spider and insect data. Figure 2. Chickadee Population Average Growth Rate and Percentage of Nonnative. The graph shows chickadee population growth rate (r) versus nonnative plants, with a replacement level at r = 0.0. 1. Respond to parts A, B, C, D, E, F, G, and H, and all subparts. A. Describe one reproductive strategy used by a K-selected species such as the chickadee. B. Based on the information provided, explain how a decrease in spider populations could affect a lower trophic level. C. Based on the data in Figure 1, identify the number of spiders per sample at 25% nonnative plants. D. Based on the data in Figure 1, describe the trend in the number of insects per sample in relation to the percentage of nonnative plants. E. Scientists hypothesized that the population of chickadees would be stable or growing with fewer than 25% nonnative plants. Describe one way that the data in Figure 2 support this hypothesis. F. Insect biodiversity is important to maintain ecosystem health. A group of students was interested in learning about factors that affect ant biodiversity. They located two study sites near their school: a frequently mowed urban park and an unmowed grassland. The students used traps designed to collect ants. They loaded 10 of the traps with the same food and placed them randomly at different locations within each site. Students collected the traps after 24 hours and counted the number of different ant species in each trap to determine species richness. i. Identify a likely scientific question for the students’ investigation of ant diversity. ii. Identify the dependent variable in the students’ investigation. G. The data from the student investigation of ant diversity are shown in the following table. An “X” in the table indicates that the species was present at that site. Ant Species Present in an Urban Park and Unmowed Grassland | Site | Species A | Species B | Species C | Species D | Species E | Species F | |---|---|---|---|---|---|---| | Urban park | X | | | X | X | | | Grassland | X | X | X | X | | X | i. Explain why the ant community of the unmowed grassland would be more likely to recover from a disturbance, such as a flood or fire, than the ant community in the mowed urban park would. ii. Explain how the results of the investigation could have been altered if students had measured ant biodiversity at a paved playground rather than in the grassland. H. Habitat fragmentation has impacts on a variety of species. Paved roads can lead to habitat fragmentation. Describe one effect that a paved road in a forest can have on animal species such as deer or bears.