Populations — Free AP Environmental Science Review Games.
This unit covers population growth, carrying capacity and demographic transition — essential concepts for AP Environmental Science. Use our interactive study games to test your understanding, or review questions in traditional format below.
Pick a mode. Play.
Answer questions as fast as you can. 2 minutes on the clock. Build streaks for bonus points!
Don't want to play?
Review the questions traditionally. Click to expand.
Questions loading...
Focus on understanding.
Focus on understanding core concepts before memorizing details. Use the game modes to test yourself repeatedly — spaced repetition is proven to boost long-term retention.
Ready for college?
See which colleges accept your AP Environmental Science score.
This unit covers population growth, carrying capacity and demographic transition — essential concepts for AP Environmental Science. Use our interactive study games to test your understanding, or review questions in traditional format below.
Key Concepts Breakdown
1 Population Growth
Students must understand the difference between exponential and logistic growth models and be able to interpret and calculate population growth using biotic potential and limiting factors. Exponential growth occurs when resources are unlimited, producing a J-shaped curve, while logistic growth produces an S-shaped curve as the population approaches carrying capacity. Students should also know how to calculate population growth rate using births, deaths, immigration, and emigration.
Key Points
- Exponential growth: J-curve, unlimited resources, described by dN/dt = rN
- Logistic growth: S-curve, resources limited, growth slows as population nears carrying capacity (K)
- Growth rate (r) = (births + immigration) − (deaths + emigration); expressed per 1000 or as a percentage
- Biotic potential is the maximum growth rate under ideal conditions; actual growth is always lower due to environmental resistance
A population of rabbits numbers 500. In one year, there are 150 births, 50 deaths, 10 immigrations, and 10 emigrations. Calculate the population growth rate (%) and the new population size.
Net change = (150 + 10) − (50 + 10) = 100 individuals. Growth rate = 100 / 500 = 0.20, or 20%. New population = 500 + 100 = 600. On the AP exam, this type of calculation is common in free-response questions and requires showing each arithmetic step clearly.
2 Carrying Capacity
Carrying capacity (K) is the maximum population size an environment can sustainably support given available resources such as food, water, space, and shelter. Students must know the difference between density-dependent and density-independent limiting factors and how each affects population size relative to K. Populations that overshoot K will experience a dieback or crash, which is a key concept in AP exam scenarios.
Key Points
- Carrying capacity (K) is set by limiting factors: food, water, space, shelter, and disease
- Density-dependent factors intensify as population density increases (predation, disease, competition, starvation)
- Density-independent factors affect population regardless of density (natural disasters, climate, pollution)
- Overshoot and dieback: population exceeds K temporarily, then crashes due to resource depletion
A graph shows a deer population that rises rapidly, overshoots a carrying capacity of 2,000, peaks at 3,500, then crashes to 800. Identify what is most likely occurring and classify the limiting factors involved.
When the population exceeds K = 2,000, food and habitat become over-depleted—these are density-dependent limiting factors because their impact intensifies with crowding. The crash to 800 reflects starvation and increased disease pressure. On the AP exam, interpreting population graphs and correctly labeling K and classifying limiting factors are both heavily tested skills.
3 Demographic Transition
The demographic transition model (DTM) describes how countries shift from high birth and death rates to low birth and death rates as they industrialize and develop economically. Students must be able to identify the four stages, explain what drives changes in birth and death rates at each stage, and connect the model to concepts like population momentum and age-structure diagrams. The AP exam frequently asks students to match a country's characteristics or pyramid shape to a specific DTM stage.
Key Points
- Stage 1: high birth rate, high death rate → slow growth (pre-industrial societies)
- Stage 2: death rate drops (medicine, sanitation), birth rate stays high → rapid population growth
- Stage 3: birth rate begins to fall (education, urbanization, women's rights) → growth slows
- Stage 4: low birth rate, low death rate → stable or declining population; age structure shifts toward older populations
A country has an age-structure diagram shaped like a wide-based triangle with a very large youth cohort, a declining adult cohort, and a small elderly cohort. Its infant mortality rate has dropped sharply in the past decade but its total fertility rate remains at 5.2. In which DTM stage is this country, and what population trend should be expected?
The wide base (large youth cohort) and high TFR of 5.2 combined with recently falling death rates indicate Stage 2 of the DTM. In Stage 2, death rates decline before birth rates do, so rapid population growth is expected. Even if birth rates begin to fall soon, population momentum—driven by the large number of young people who will reach reproductive age—will continue driving growth for decades, a concept the AP exam tests explicitly.
Questions, answered.
What is Populations?
Populations is Unit 3 of AP Environmental Science, covering population growth, carrying capacity and demographic transition.
How to study for AP Environmental Science Unit 3?
Start with the Quick Summary above, review the Key Concepts, then test yourself with our interactive study games. Aim for 80%+ accuracy before moving on.
How many questions are in this unit?
This unit has 30+ review questions across 5 different game modes.