A coastal community is experiencing declining water quality due to agricultural runoff containing excess nitrogen and phosphorus. Local ecologists propose restoring a 50-hectare freshwater wetland that was drained 40 years ago for development. The restored wetland would serve as a natural filter for nutrients while providing habitat for native species. The community must evaluate the ecological and economic benefits of this restoration project.
Parameter
Current Degraded Site
Expected Post-Restoration
Net Primary Productivity (NPP)
1,200 kcal/m²/yr
8,400 kcal/m²/yr
Nitrogen removal rate
5 kg/hectare/yr
180 kg/hectare/yr
Phosphorus in incoming water
0.85 mg/L
0.85 mg/L
Phosphorus in outgoing water
0.78 mg/L
0.12 mg/L
Water flow through wetland
2.4 × 10⁶ liters/day
2.4 × 10⁶ liters/day
A.
Identify the specific biogeochemical cycle that does NOT have a significant atmospheric reservoir and is most likely to limit primary productivity in freshwater wetland ecosystems.
B.
Describe one ecosystem service, other than nutrient filtration, that the restored wetland would provide to the coastal community.
C.
Explain how the process of denitrification in the restored wetland would reduce the amount of nitrogen reaching coastal waters, including the form of nitrogen that is removed from the ecosystem.
D.
Calculate the amount of energy, in kcal/m²/yr, that would be available to secondary consumers in the restored wetland food web. Show your work. Based on Table 1, the expected net primary productivity (NPP) of the restored wetland is 8,400 kcal/m²/yr. Energy transfer efficiency between trophic levels in wetland ecosystems averages 10%.
E.
Calculate the percent change in net primary productivity between the current degraded site and the expected post-restoration wetland. Show your work. Based on Table 1, the restored wetland is expected to have a net primary productivity of 8,400 kcal/m²/yr, while the current degraded site has an NPP of 1,200 kcal/m²/yr.
F.
Propose one realistic management practice the restoration team could implement to prevent the establishment of invasive plant species, such as purple loosestrife or phragmites, that could outcompete native wetland vegetation for resources.
G.
Calculate the total mass of phosphorus, in kilograms per year, that the restored wetland would remove from the water. Show your work. (Note: 1 kg = 1 × 10⁶ mg) Based on Table 1, phosphorus concentration in water entering the wetland is 0.85 mg/L, and phosphorus in water leaving the wetland is expected to be 0.12 mg/L. The water flow through the restored wetland is 2.4 × 10⁶ liters per day. The wetland operates year-round.
What the Calculation FRQ asks
This is FRQ 3 on the AP Environmental Science exam. You get an environmental problem with numbers, explain the science, run calculations that show the scale of the problem, and propose a solution. Three parts are calculations worth 2 points each, and on some questions the solution comes before them.
Name a concept, source, or practice in the scenario
1 pt
B
Part B: Describe
Describe an environmental problem or service
1 pt
C
Part C: Explain
Explain how a process or change affects the system
1 pt
D
Part D: Calculation
Set up and solve a calculation, with units
2 pts
E
Part E: Calculation
A second calculation, often building on the first
2 pts
F
Part F: Solution
Propose a realistic solution
1 pt
G
Part G: Calculation
A third calculation tied to the problem
2 pts
How Calculation FRQ practice works
Each question follows the exam’s format, from the full prompt to a score on every part.
1
Read the full question
The scenario, the numbers you need, and every part, laid out the way the exam shows them.
2
Write your response
A timer runs while you write. Pause it or turn it off, and your response saves as you go.
3
Submit for a score out of 10
Your response is scored against the scoring guidelines written for that question. Your first score is included.
Feedback on every part
A summary at the top tells you what to work on next. Below it, each part shows whether you earned the point and what the scoring guidelines were looking for.
The student correctly identifies pollination as an ecosystem service provided by pollinators that benefits crop production on the farms. This is a valid and clearly stated response.
Part B(B1): 1/1 point
The student describes a specific environmental problem — aquifer/groundwater depletion — and provides the mechanism by referencing the 60% absorption efficiency and the resulting waste of the remaining 40%. This meets the requirement for a described problem with a mechanism or consequence.
Part E(E2): 0/1 point
The student calculates the difference as 1,047,500 gallons, but the correct answer is 1,147,500 gallons. The arithmetic error (3,442,500 − 2,295,000 = 1,147,500, not 1,047,500) results in an incorrect final answer. No credit for the answer point.
Detailed feedback on a practice Calculation FRQ
Questions about the Calculation FRQ
How many responses can I get scored?
You can read every question without a plan. Your first scored response is included. A plan unlocks unlimited scoring.
How do I show my work?
Type each step with its units, the way you’d write it on paper. You can also switch the editor to handwrite, write on paper, and add a photo of your page.
What calculations come up?
Percent change, unit conversions, rates, and totals, like the land, water, or energy a plan needs. Each calculation part is worth 2 points.
How is FRQ 3 different from FRQ 2?
Both ask about an environmental problem and a solution. FRQ 3 adds calculations worth 2 points each. FRQ 2 centers on reading data.
Are these real College Board questions?
No. We wrote them in the AP format, with the same parts, and wrote scoring guidelines for each one.
More AP Environmental Science practice
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Design an Investigation questions with the scenario, the figures, and every part.
