♻️AP Environmental Science
♻️AP Environmental Science
FRQ 1 – Experimental Design
Unit 1: The Living World: Ecosystems
Practice FRQ 1 of 221/22
1. Phytoplankton are microscopic photosynthetic organisms that form the base of aquatic food webs. In freshwater lakes, phytoplankton populations are influenced by nutrient availability, particularly nitrogen and phosphorus. These nutrients enter lakes through surface runoff from surrounding watersheds.
A. Describe one step in the nitrogen cycle that converts atmospheric nitrogen () into a form that can be used by phytoplankton.
B. Explain how an increase in phytoplankton populations in Lake A could affect the dissolved oxygen levels available to fish populations at night.
Figure 1. Average Nutrient Concentrations in Lake A and Lake B (mean ± standard error).
C. Based on the data in Figure 1, identify the phosphorus concentration in Lake B.
Figure 2. Gross Primary Productivity (GPP) in Lake A and Lake B Over Time.
D. Based on the data in Figure 2, describe the trend in gross primary productivity in Lake A from January through July.
E. Scientists hypothesized that lakes receiving agricultural runoff would have higher gross primary productivity than lakes surrounded by forest. Describe one way that the data in Figure 2 support this hypothesis.
F. Phytoplankton diversity is an important indicator of ecosystem health. A group of students wanted to investigate factors that affect phytoplankton diversity in local ponds. They selected two study sites: Pond X, which receives runoff from a parking lot, and Pond Y, which is located in a nature preserve. The students collected 500 mL water samples from 8 randomly selected locations in each pond. They used microscopes to identify and count the number of different phytoplankton species in each sample.
i. Identify a likely scientific question for the students' investigation of phytoplankton diversity.
ii. Identify the independent variable in the students' investigation.
| Lake | Species 1 | Species 2 | Species 3 | Species 4 | Species 5 | Species 6 | Species 7 |
|---|---|---|---|---|---|---|---|
| Lake A | X | X | X | ||||
| Lake B | X | X | X | X | X | X |
G. The data from the student investigation of phytoplankton diversity are shown in the following table. An 'X' in the table indicates that the species was present at that site.
i. Explain why the phytoplankton community in Lake B would be more resilient to an environmental disturbance, such as a sudden temperature increase, than the phytoplankton community in Lake A would.
ii. Explain how the energy transfer efficiency from phytoplankton to zooplankton would be affected if only 8% of the energy at the phytoplankton trophic level was transferred to the zooplankton trophic level instead of the typical 10%.
H. Describe one negative effect that eutrophication can have on fish populations in a lake ecosystem. Eutrophication is a common problem in lakes that receive excess nutrients from agricultural runoff.
