Early Solutions to the 2026 AP Environmental Science FRQs | Step by Step

AHighest current species richness

Task: Based on the diagram, identify the elevation zone with the highest species richness in the current distribution.

1. Species richness means the number of different species present, not the number of individual birds.
2. The low-elevation zone contains species A, B, C, and D.
3. Its richness is therefore 4, higher than the value for any other current zone.

BClimate at high elevation

Task: Describe one climate condition at high elevations that differs from conditions at low elevations.

1. As elevation increases, air pressure decreases.
2. Rising air expands and cools, so mountain climates are generally colder than nearby low-elevation climates.

CEffect on a low-elevation predator

Task: A low-elevation predator currently eats species C and D. Describe what could happen to that predator under the predicted prey changes.

1. The predator currently depends on C and D as food.
2. In the predicted future low-elevation zone, neither C nor D remains; only species A is shown.
3. Loss of its established prey base reduces food availability, survival, and reproduction unless the predator switches prey or follows the prey upslope.

DGeneralist C versus specialist E

Task: Explain why species C, a generalist, and species E, a specialist, are predicted to respond differently to climate change.

1. Species C currently occurs in all four elevation zones, evidence of a broad realized niche and wide climate tolerance.
2. A generalist can usually use a wider range of habitats or resources, so C can shift upward and remain in several zones.
3. Species E occurs only at high elevation, evidence of a narrow niche tied to cool mountaintop conditions.
4. As suitable climate moves upslope, the available land area shrinks and ends at the summit. E has no higher habitat to occupy.

ELower resilience of the future bird community

Task: Explain why the future low-elevation bird community would be less likely to recover from natural disruptions.

1. The current low-elevation community has four species; the predicted future community has only one.
2. Greater biodiversity often provides functional redundancy: more than one species can perform similar ecological roles.
3. With only one species, a drought, disease, fire, or severe storm affecting that species can remove most ecological function, so recovery is less likely.

FIndependent variable in Experiment 1

Task: Identify the independent variable.

1. The independent variable is the factor deliberately changed by the researchers.
2. Temperature changes from 27°C to 32°C to 37°C, while sediment is absent from every tank.
3. The number of bleached corals is the dependent variable because it is measured.

GScientific question for Experiment 1

Task: Identify a likely scientific question.

1. Name the manipulated variable: seawater temperature.
2. Name the measured response: number of bleached corals after 30 days.
3. Phrase the relationship as a testable question.

HEffect of the Experiment 2 modification

Task: Explain how holding temperature constant while varying sediment could affect the results.

1. Experiment 2 changes only sediment amount; temperature stays at 27°C.
2. Controlling temperature removes it as a confounding variable, so bleaching differences can be attributed more directly to sediment.
3. Suspended sediment increases turbidity, reducing the light available to the corals' symbiotic photosynthetic algae.
4. Lower photosynthesis reduces chemical energy supplied to coral. Sediment can also smother coral or interfere with feeding and gas exchange.

IIce-albedo positive feedback

Task: Describe a positive feedback loop caused by loss of polar ice and snow.

Bright ice reflects a large fraction of incoming sunlight. When it melts, darker ocean or land is exposed and absorbs more solar radiation. The added warming causes still more melting, amplifying the original change.

JProblem for an Arctic species

Task: Describe one problem that polar bears, ringed seals, or another Arctic species faces because of warming.

1. Sea ice is habitat: it supplies hunting access, resting locations, breeding areas, and travel routes.
2. Polar bears use sea ice as a platform for hunting ringed seals.
3. With less ice, bears may swim farther and spend more energy while obtaining less food, harming body condition, reproduction, and survival.

ARenewable source used for electricity

Task: Identify one renewable energy source used to generate electricity.

Wind is continually replenished by atmospheric circulation driven mainly by uneven solar heating. Moving air turns turbine blades, and the rotating shaft drives a generator.

BHighest consumption in 2010

Task: Identify the energy source with the highest consumption in 2010.

At 2010, the petroleum line is approximately 34 quadrillion BTU, above natural gas and coal in the low 20s, nuclear near 8, and renewables near 4-5.

CCoal-consumption pattern, 1960-2020

Task: Describe the pattern in U.S. coal consumption over the full interval.

1. From about 1960 to the mid-2000s, coal consumption generally rose, with fluctuations, from roughly 9 to about 22-23 quadrillion BTU.
2. After about 2010, coal consumption declined sharply to approximately 9 quadrillion BTU by 2020.

DWhy coal use changed from 2010 to 2020

Task: Explain one likely reason for the change in coal use.

1. Hydraulic fracturing and horizontal drilling increased the supply of natural gas, lowering its price.
2. Utilities replaced some coal-fired generation with natural-gas generation.
3. Natural gas emits less sulfur pollution and less CO₂ per unit of electricity than coal, adding an environmental and regulatory incentive.
4. The graph is consistent with this mechanism because natural-gas use rises while coal use falls.

EHow fossil fuels generate electricity

Task: Explain the energy-conversion process.

1. Combustion releases the fuel's chemical energy as heat.
2. The heat boils water, creating high-pressure steam that spins a turbine.
3. The turbine rotates a generator; a changing magnetic field induces an electric current.
4. The electricity is transmitted through the grid.

FNegative impact of nuclear energy

Task: Identify one negative impact associated with nuclear energy.

Spent nuclear fuel remains radioactive for long periods. It needs engineered containment, monitoring, and protection against leakage, accidents, and unauthorized access.

GEnvironmental problem from ocean warming

Task: Describe one problem other than coral bleaching.

1. Water expands as its temperature increases; this process is called thermal expansion.
2. Thermal expansion raises sea level.
3. Higher sea level increases coastal flooding and erosion and can push salt water into freshwater aquifers and wetlands.

HHow excess nutrients harm an aquatic ecosystem

Task: Explain the negative effect of increased nitrates and phosphates.

Rapid algal growth also increases turbidity and blocks light. When the bloom and shaded plants die, decomposer bacteria consume the biomass and use dissolved oxygen. Hypoxic or anoxic water cannot support many fish and invertebrates.

I(i)Solution that still permits crop cultivation

Task: Propose a realistic solution to reduce nutrient pollution while still allowing crops to be grown.

1. Keep most of the field in cultivation.
2. Establish strips of grasses, shrubs, or trees between the cropped land and nearby streams.
3. The vegetation slows runoff, increases infiltration, absorbs nutrients through roots, and traps nutrient-rich sediment before it reaches the water.

I(ii)Additional advantage of the solution

Task: Justify the buffer-strip solution with an advantage other than reducing nutrient runoff.

1. Plant roots bind soil particles and stabilize field margins and streambanks.
2. Less soil erosion preserves fertile topsoil, supporting long-term agricultural productivity.
3. The buffer may also create habitat and a movement corridor for wildlife, but one explained advantage is enough.

AConsequence of a smaller ocelot population

Task: Identify one environmental consequence.

1. Ocelots exert top-down control on pocket mice.
2. Fewer ocelots reduce predation, so pocket-mouse abundance may rise.
3. More herbivorous rodents consume more plants and seeds, reducing shrubland biomass and altering habitat for other species.

BPercent change in occupied counties

Task: Calculate the percent change from the historical 25 counties to the current 4 counties. Show the work.

The negative sign means the number decreased. State either “-84%” or “an 84% decrease,” not “a -84% decrease.”

CPopulation doubling time

Task: Calculate how long the population takes to double at a constant annual growth rate of 2.8%.

Method 1: Rule of 70

Method 2: Exact compound-growth check

The exact result confirms the Rule-of-70 estimate.

DEnergy if ocelots ate only carnivores

Task: Explain how the primary-production energy available to ocelots would change if they ate carnivorous snakes instead of pocket mice.

1. Pocket mice eat plants, so they are primary consumers. Eating them gives the ocelot a relatively short food chain.
2. A carnivorous snake has already consumed another animal. Eating it adds at least one trophic transfer before energy reaches the ocelot.
3. At every transfer, most energy is used in metabolism or lost as heat and waste; only about 10% is commonly approximated as available to the next trophic level.

EPocket mice consumed per day

Task: An ocelot eats 720 g of food per day; 46% is pocket mice by weight; each mouse averages 43 g. Calculate the number of mice.

1. Find the daily mass of pocket mice: 720 g × 0.46 = 331.2 g.
2. Divide by mass per mouse.

The calculation gives 7.70 mice. In this counting context, report approximately 8 whole mice per day.

F(i)Solution to vehicle collisions

Task: Propose a realistic solution that reduces ocelot deaths from vehicles.

1. Use collision records, tracking data, and habitat corridors to locate frequent crossing points.
2. Build wildlife underpasses or overpasses at those locations.
3. Add roadside fencing that guides ocelots toward the safe passages instead of allowing them onto the roadway.

F(ii)Additional advantage of wildlife crossings

Task: Explain one advantage other than reducing road deaths.

1. Roads fragment habitat and restrict movement between population groups.
2. Crossings reconnect fragments, allowing ocelots to reach mates, prey, and other resources.
3. Movement between groups increases gene flow, which can reduce inbreeding and help maintain genetic diversity in this very small population.