AP Environmental Science Unit 2 — The Written Half: Three Free-Response Questions, Worked Out Loud
In May, three written questions carry forty percent of your AP Environmental Science score.
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AP Environmental Science Unit 2 — The Written Half: Three Free-Response Questions, Worked Out Loud
Forty percent of the AP Environmental Science score is written. Section two of the exam is three free-response questions, ten points each, in seventy minutes, with a calculator allowed on both sections 1.
Each question is built out of parts, and each part is worth one or two points. The course prints scoring guidelines for its own sample questions, and they read as a list of the answers that earn the points — one point for naming a mechanism, one point for the labelled calculation, nothing for the right idea that never reached the page 1.
That is how an answer can be ecologically sound and still score nothing: the verb decides what is being marked. This edition covers the three question types, the verbs that open them, and five Unit 2 questions worked through in full.
The three question types
Question 1 — design an investigation. A scenario arrives with a model or a diagram, and the question asks what you would measure and how you would measure it.
Question 2 — analyze and interpret quantitative data. A table, chart, or graph has to be read, described, and explained.
Question 3 — analyze an environmental problem doing calculations. A scenario with numbers; you work the numbers and label the units.
All three also draw on the unit's concepts and ask for a solution to an environmental problem, and that last part carries real weight. Proposing and justifying solutions is the largest share of the written section at 26 to 34 percent of it; mathematical routines are 20 percent, and explaining concepts is 13 to 20 percent 1.
What each verb asks for
- Identify — give information about a specified topic, with no elaboration or explanation.
- Describe — give the relevant characteristics of the thing: what it is like, what it does, what it has.
- Explain — give how or why something happens, with reasoning or evidence attached. Explain how usually wants the relationship or process; explain why usually wants the reason. "Give one reason" is the same task.
- Calculate — perform the mathematical steps, including the substituted numbers and the unit written on the answer. Showing your work is required.
- Justify — give evidence and reasoning that support, qualify, or defend a claim.
- Make a claim — make an assertion based on evidence or knowledge.
- Propose a solution — offer a solution that follows from evidence or knowledge.
All seven definitions come from the exam's own task-verb list 1.
The five questions, worked
Question 1 — design an investigation. A hillside in Ohio was surface-mined for coal and re-graded twenty years ago; the land around it is oak and hickory forest. Design an investigation to find out whether the reclaimed ground is developing toward that forest.
Hypothesis: as the reclaimed ground ages, its plant species richness and its soil nitrogen rise toward the values in the surrounding forest. Independent variable: the site — reclaimed hillside against reference forest. Dependent variable: plant species richness per plot and soil organic matter, sampled the same way on both sites. Control: the reference forest, same plot size, same season, same method — a control is a comparison, not a before. Why many plots: one plot cannot separate a real difference from the accident of where you stood that morning. The trap sits in the control: a comparison site sampled differently from the treatment measures your method rather than your hillside.
Question 2 — read the data. Two prairie remnants, the same size, in the same county, sampled the same way. Site A: 12 species, 480 individuals, commonest species 45. Site B: 9 species, 480 individuals, commonest species 300.
Site A has the greater species richness. The commonest species holds 45 of 480, a little under 10 percent, against 300 of 480, which is 62.5 percent. Site A is even; at Site B close to two of every three individuals belong to one species. If a disease removed the commonest species, Site A is the one more likely to keep working, because its numbers and roles are spread across many species — at Site B the loss takes about two thirds of the living matter in the plot. The trap is treating the species count as the whole of diversity.
Question 3 — the calculation. Every winter, Mexico's protected-areas commission and the World Wildlife Fund map the forest area occupied by monarch butterfly colonies. The record was about 18.19 hectares in 1996–97, and the lowest year was 0.67 hectares in 2013–14 2. The survey published in March 2026 put the winter of 2025–26 at 2.93 hectares, a 64 percent increase on the 1.79 hectares of the winter before 3. The second-lowest winter on that series is 2.2 acres, about 0.9 hectares, in 2023–24 4.
From the record to this winter is a fall of 15.26 hectares; 15.26 divided by 18.19 is about 0.84, so a decrease of roughly 84 percent. The wintering area is about 16 percent of its record. Both statements are true because a percent change is a ratio, and the number you divide by decides how large it looks. The assumption underneath the whole survey is that area of forest stands in for number of butterflies — a proxy, not a count.
Question 4 — the control. A dam is built across a river, and several years later biologists report that the salmon population downstream has declined. The best control is the health of that population before any dam was built: it is the only option showing a population the dam never touched. The option "before people lived in the area" moves two things at once, the dam and the people, and the two middle options sit inside the disturbance itself 1.
Question 5 — propose and justify. A coastal town plans to fill a salt marsh to build a parking lot; the marsh takes the water on every spring tide and shelters juvenile fish. The marsh is providing a regulating service — it holds flood water and takes the energy out of storm surge. A solution is to put the lot on ground the town has already paved and leave the marsh where it is, and the justification names the mechanism: leave the marsh alone and the flood water still has somewhere to go.
Four traps the written half sets
Answering a different verb. Describe where the question said explain keeps the describe point at best, and the explain point is gone.
A correct number with no work and no unit. The calculation point is for the steps and the labelled answer, not for the arithmetic on its own.
Answering one where the question asked for two. "Describe two impacts" means one impact is one point, and the second point stays on the page.
Proposing one solution and justifying a different one. The justification has to connect your own proposal to its effect, and repeating the claim is not reasoning.
Write the answer the verb asked for, and put the mechanism on the page. Run the practice set once more before the test.
References
- 1College Board, AP Environmental Science Course and Exam Description
apcentral.collegeboard.org
- 2Monarch Butterfly Fund, Population Status
monarchconservation.org
- 3
- 4WWF, Monarch Butterfly Survey Report 2023-2024
worldwildlife.org
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