AP Environmental Science Unit 3: Populations Practice Exam

Assessment for Unit 3: Populations

Estimated Time: 60 minutes

Exam Details

Questions: 21 total (20 multiple choice, 1 short answer)
Time: 60 minutes (recommended)
Topics Covered: Unit 3: Populations
Format: Multiple Choice, Short Answer questions matching real exam difficulty
Scoring: Instant results with detailed explanations

A. Multiple-Choice Questions (20 Questions)

Select the one best answer for each question.

Refer to the figure below.

1. [Skill: 2A | Topic: 3.1] A conservation biologist monitored two bird species (Species A and Species B) in the same wetland for 10 years. In year 6, a large storm converted much of the wetland to open water and changed plant composition. [Image Cue]: Line graph, "Population size of two bird species before and after a habitat disturbance"; x-axis: Year (1–10) with a vertical dashed line at Year 6 labeled "Storm disturbance"; y-axis: Population size (number of individuals). Key trends: Species A remains relatively stable from Years 1–5, then declines sharply from Years 6–10. Species B remains relatively stable from Years 1–5, then increases from Years 6–10. Based on the graph, which statement best identifies the likely niche strategies of Species A and Species B?

(A)Species A is a generalist and Species B is a specialist, because generalists outcompete specialists after disturbances.(B)Species A is a specialist and Species B is a generalist, because specialists are more advantaged in constant habitats and generalists are more advantaged in changing habitats.(C)Both Species A and Species B are specialists, because both persisted for the first 5 years in the same habitat.(D)Both Species A and Species B are generalists, because both survived the storm disturbance.

2. [Skill: 1A | Topic: 3.1] A small mammal species lives only in old-growth conifer forests and feeds primarily on a single lichen species found on mature trees. A nearby second mammal species occupies forests, suburban parks, and agricultural edges and consumes a wide variety of plant material and insects. Over the next decade, the region is expected to experience increased wildfire frequency and post-fire vegetation shifts. Which prediction is most consistent with ecological niche breadth and the expected environmental changes?

(A)The old-growth conifer specialist is likely to be less affected because specializing on one food source reduces competition after wildfire.(B)The old-growth conifer specialist is likely to be more vulnerable because specialists are advantaged mainly when habitats remain constant.(C)The second species is likely to decline because generalists require stable habitats to maintain many food sources.(D)Both species are equally likely to persist because wildfire creates new niches for all species regardless of specialization.

3. [Skill: 2A | Topic: 3.1] Researchers compared the resource use of two insect species found in a grassland ecosystem. [Image Cue]: Data table, "Resource use of two insect species"; columns: Species, Number of host plant species used for feeding, Nesting habitat types used. Data: Species X uses 6 host plant species and 3 nesting habitat types; Species Y uses 1 host plant species and 1 nesting habitat type. The grassland has been stable for decades, but models predict that precipitation patterns will become highly variable over the next 20 years, changing plant community composition. Which statement best predicts how the two insect species will be affected as conditions become more variable?

(A)Species X will be more likely to persist because a generalist strategy is typically favored as habitats change.(B)Species Y will be more likely to persist because specialists are typically favored as habitats change.(C)Both species will be equally likely to persist because precipitation variability affects only abiotic factors, not niches.(D)Species X will be more likely to go extinct because using many host plants increases dependence on any single plant species.

Refer to the figure below.

4. [Skill: 2A | Topic: 3.2] A field ecologist compares two species living in the same region. [Image Cue]: Table, "Life-History Traits of Two Species", columns = Trait / Species A / Species B; rows include: Adult body size (large vs small), Age at first reproduction (late vs early), Average offspring per reproductive event (few vs many), Parental care (high vs low/none), Life span (long vs short), Typical habitat (stable vs frequently disturbed). Based on the traits in the table, which of the following conclusions is most scientifically supported?

(A)Species A is more likely K-selected because it produces few offspring, has a long life span, and tends to live in stable environments with relatively high competition.(B)Species A is more likely r-selected because it produces few offspring and invests in high parental care, allowing rapid population growth in unpredictable environments.(C)Species B is more likely K-selected because it matures early, produces many offspring, and is successful in disturbed habitats where competition is low.(D)Species B is more likely K-selected because producing many offspring increases survival in stable environments near carrying capacity.

5. [Skill: 1A | Topic: 3.2] A researcher studies an annual plant species. In a greenhouse with unlimited water, nutrients, and space and with no herbivores, each mature plant produces an average of 12,000 viable seeds during a growing season. In a nearby field, the same species produces an average of 900 viable seeds per plant due to drought stress and insect herbivory. Which of the following values best represents the plant population’s biotic potential?

(A)12,000 viable seeds per plant per growing season under greenhouse conditions(B)900 viable seeds per plant per growing season in the field(C)The maximum number of individuals the field can support over time (carrying capacity)(D)The fraction of seedlings that survive to adulthood in the field

6. [Skill: 4A | Topic: 3.2] A remote island has a native seabird that lays one egg per year, reaches reproductive maturity after several years, and has a long life span. A new invasive rat species arrives via ships; the rats reproduce multiple times per year and produce large litters. Within a decade, seabird nesting success and population size decline sharply. Which of the following best explains why the native seabird is particularly vulnerable to the invasive rats?

(A)The seabird is K-selected, so low reproductive output and slower population growth make it less able to recover from increased predation and competition caused by an r-selected invader.(B)The seabird is r-selected, so it experiences the highest competition in stable environments and is therefore outcompeted by the rats.(C)K-selected species typically have higher biotic potential than r-selected species, so the seabird population declines because it overuses its habitat’s resources.(D)Invasive species are typically K-selected, so the rats reduce seabird numbers by stabilizing the island ecosystem at a lower carrying capacity.

Refer to the figure below.

7. [Skill: 2A | Topic: 3.3] A researcher compares survivorship among three species in the same ecosystem. [Image Cue]: Line graph, "Survivorship Curves for Three Species"; x-axis = Age (relative, from 0 to maximum lifespan); y-axis = Proportion of original cohort surviving (logarithmic scale, from 1.0 down to 0.001). Curve A stays near 1.0 through early and middle ages, then drops steeply late in life. Curve B declines at a relatively constant rate across all ages (straight diagonal line on a log scale). Curve C drops steeply early in life, then levels off and declines slowly for the remaining ages. Which choice correctly matches each curve with survivorship type AND the most likely reproductive strategy?

(A)A = Type I (K-selected), B = Type II (K-selected), C = Type III (r-selected)(B)A = Type II (r-selected), B = Type III (K-selected), C = Type I (K-selected)(C)A = Type III (r-selected), B = Type I (K-selected), C = Type II (K-selected)(D)A = Type I (r-selected), B = Type II (r-selected), C = Type III (K-selected)

8. [Skill: 1B | Topic: 3.3] A field ecologist tracks a cohort of 1,000 newly produced offspring of an aquatic invertebrate. The number of individuals still alive at each age is shown below. Age (relative units): 0, 1, 2, 3, 4 Survivors: 1000, 120, 60, 45, 40 Which of the following best explains the survivorship curve expected for this species and what it implies about the species' life-history strategy?

(A)Type I survivorship; most individuals survive until old age, indicating K-selection with high parental care(B)Type II survivorship; individuals have an approximately constant probability of death at any age, indicating K-selection(C)Type III survivorship; high early mortality with relatively higher survivorship after early life, indicating r-selection(D)Type III survivorship; high late-life mortality with relatively higher survivorship early in life, indicating K-selection

Refer to the figure below.

9. [Skill: 4.A | Topic: 3.4] A researcher monitored a zooplankton population in a closed freshwater pond (no immigration or emigration) after an unusually warm spring increased reproduction rates. The data are shown in the graph. [Image Cue]: Line graph, "Zooplankton Population Size Over Time". x-axis: Time (weeks 0–20). y-axis: Population size (individuals). A dashed horizontal line labeled "K" at 500 individuals. The population increases rapidly from 100 at week 0 to 800 at week 8, then declines to 300 by week 12, and then fluctuates between about 350 and 550 from weeks 12–20. Which of the following best explains the pattern shown after week 8?

(A)The population exceeded carrying capacity (overshoot), depleting resources and contributing to dieback, followed by fluctuations around K.(B)The population reached carrying capacity at week 8, and the decline indicates that K permanently decreased to 300 individuals.(C)The population decline indicates that carrying capacity was never exceeded, because overshoot cannot occur in closed systems.(D)The population exceeded carrying capacity, and the resulting dieback shows that carrying capacity increases as resources are consumed.

10. [Skill: 1.A | Topic: 3.4] A population of feral goats was introduced to an island with limited freshwater sources and slow-growing shrubs. For several years, the goat population increased rapidly. Later, island surveys documented heavy vegetation loss, increased competition at watering sites, and a sudden increase in deaths from starvation and disease. Which of the following best links the observations to carrying capacity (K) and its ecological impacts?

(A)The goat population exceeded K (overshoot), leading to resource depletion and then dieback due to limited food and water.(B)The goat population reached K, which increased reproduction and therefore caused the starvation and disease.(C)The goat population experienced a temporary decrease in K that is unrelated to resources, because K is determined only by genetic traits.(D)The goat population avoided overshoot because competition and disease are density-independent factors that prevent populations from exceeding K.

Refer to the figure below.

11. **1. [Skill: 3.A | Topic: 3.5]** A student monitors the population of a freshwater zooplankton species in an enclosed tank. The student initially adds a large amount of algal food and maintains constant temperature and light. On day 18, the student stops adding algae, and available food steadily declines. The graph shows zooplankton population size over 30 days. Which of the following best explains the overall pattern in the graph?

(A)The zooplankton population initially grows rapidly because resources are abundant, then growth slows near carrying capacity as resources and space become limiting, and finally the population declines when the resource base shrinks, increasing mortality and/or decreasing fecundity.(B)The zooplankton population declines after day 18 because carrying capacity is fixed and cannot change even when resources decrease.(C)The zooplankton population levels off near carrying capacity because predators increase in the tank, causing density-independent population regulation.(D)The zooplankton population grows exponentially throughout the entire period because populations are not limited by resources in enclosed systems.

12. **2. [Skill: 1.A | Topic: 3.5]** A population of deer lives in a fenced reserve. For several years, the population size is stable. A multi-year drought reduces plant growth across the reserve, lowering the total amount of available forage. Which of the following outcomes is most likely as the drought continues, and why?

(A)Deer fecundity will decrease and mortality will increase because a shrinking resource base can lead to scarcity and unequal access to food, causing population growth to decline to, or below, carrying capacity.(B)Deer fecundity will increase because competition for limited food selects for individuals that reproduce earlier, increasing population growth above carrying capacity.(C)Deer mortality will decrease because reduced plant growth lowers the deer population’s carrying capacity, which automatically reduces death rates.(D)The deer population will remain stable because resource availability is effectively unlimited at the scale of a few years.

Refer to the figure below.

13. [Skill: 2A | Topic: 3.6] A student is analyzing an age structure diagram for Country X. Which of the following interpretations of the population growth rate in Country X is best supported by the diagram?

(A)The population is likely growing rapidly because the youngest age cohorts make up the largest proportion of the population.(B)The population is likely stable because the diagram shows equal numbers of individuals in every age cohort.(C)The population is likely declining because the oldest age cohorts make up the largest proportion of the population.(D)The population is likely decreasing because the diagram shows a higher proportion of females than males in most age cohorts.

14. [Skill: 1A | Topic: 3.6] Country Y implemented education and family planning programs, and its total fertility rate recently fell to approximately replacement level. Current age distribution in Country Y: - 0–14 years: 32% - 15–44 years: 45% - 45+ years: 23% Based on the age structure information, which outcome is most likely over the next few decades, even if fertility remains at replacement level?

(A)The population will immediately begin to decline because replacement-level fertility always causes negative growth.(B)The population will likely continue to grow for a period of time because a large cohort will soon enter reproductive ages (population momentum).(C)The population will remain constant because replacement-level fertility guarantees zero population growth in all age structures.(D)The population will shift to a rapidly declining pattern because a high proportion of individuals are already past reproductive age.

Refer to the figure below.

15. **1. [Skill: 4A | Topic: 3.7]** A researcher compares demographic indicators for two countries. [Image Cue]: Table, "Selected Demographic Indicators for Two Countries"; Columns: Country, Mean age at first birth (years), Females completing secondary school (%), Access to family planning (contraceptive prevalence, %), Government policy, Total fertility rate (births per woman). Data: Country A: 27; 88%; 72%; no pronatalist policy; TFR 1.7. Country B: 19; 41%; 28%; pronatalist tax credits for larger families; TFR 4.3. Which of the following best explains why Country B has a higher total fertility rate (TFR) than Country A? (A) Country B has a lower mean age at first birth, fewer educational opportunities for females, more limited access to family planning, and policies that encourage having more children. (B) Country B has a higher mean age at first birth and greater access to family planning, which increases the number of children per woman. (C) Country B has more females completing secondary school, which typically increases TFR by increasing earning potential. (D) Country B’s pronatalist tax credits are likely to decrease TFR because they reduce the cost of contraception and family planning.

(A)Country B has a lower mean age at first birth, fewer educational opportunities for females, more limited access to family planning, and policies that encourage having more children.(B)Country B has a higher mean age at first birth and greater access to family planning, which increases the number of children per woman.(C)Country B has more females completing secondary school, which typically increases TFR by increasing earning potential.(D)Country B’s pronatalist tax credits are likely to decrease TFR because they reduce the cost of contraception and family planning.

Refer to the figure below.

16. **2. [Skill: 4A | Topic: 3.7]** A country tracks two indicators from 2000 to 2020. [Image Cue]: Dual-line graph, "Changes in Infant Mortality and Total Fertility Rate (2000–2020)"; x-axis: Year (2000, 2005, 2010, 2015, 2020). Left y-axis: Infant mortality (deaths per 1,000 live births) decreasing from 55 (2000) to 20 (2020). Right y-axis: Total fertility rate (births per woman) decreasing from 3.6 (2000) to 2.1 (2020). Both lines show steady decline. Which statement best interprets the data using accepted demographic principles? (A) Improved access to maternal healthcare and nutrition can help reduce infant mortality, and a TFR near 2.1 suggests the population may be relatively stable over the long term. (B) Stricter immigration enforcement is the most direct cause of declining infant mortality, and a TFR near 2.1 indicates rapid population growth. (C) A decrease in the age at which females have their first child is the most direct cause of declining infant mortality, and a TFR near 2.1 means the population will quickly decline. (D) Government policies that encourage larger families are the most direct cause of declining infant mortality, and a TFR near 2.1 indicates the population is unstable because it is above replacement level.

(A)Improved access to maternal healthcare and nutrition can help reduce infant mortality, and a TFR near 2.1 suggests the population may be relatively stable over the long term.(B)Stricter immigration enforcement is the most direct cause of declining infant mortality, and a TFR near 2.1 indicates rapid population growth.(C)A decrease in the age at which females have their first child is the most direct cause of declining infant mortality, and a TFR near 2.1 means the population will quickly decline.(D)Government policies that encourage larger families are the most direct cause of declining infant mortality, and a TFR near 2.1 indicates the population is unstable because it is above replacement level.

Refer to the figure below.

17. [Skill: 4A | Topic: 3.8] [Image Cue]: Line graph, "Population Size Over Time in Coastal City Z". x-axis: Year (2010–2020). y-axis: Population (millions). Key trend: steady increase from 2010 to 2015; sharp drop in 2016; partial recovery in 2017–2020 but growth slows and levels off below the pre-2016 trend. Annotation near 2016: "Category 5 hurricane". Annotation near 2017–2018: "limited access to clean water; increased disease cases". Based on the graph and annotations, which of the following best explains the population changes in City Z after 2015?

(A)The hurricane was a density-independent factor that caused the sharp decline, and disease transmission related to limited clean water was a density-dependent factor that slowed recovery.(B)The hurricane was a density-dependent factor that caused the sharp decline, and limited clean water was a density-independent factor that slowed recovery.(C)Both the hurricane and the disease outbreak were density-independent factors, because both reduced population size regardless of population density.(D)Both the hurricane and limited access to clean water were density-dependent factors, because both occurred in a coastal city with a growing population.

18. [Skill: 5A | Topic: 3.8] A country has an annual population growth rate of 2.8%. After expanded access to education and family planning, its growth rate decreases to 1.4%. Using the rule of 70, which of the following best compares the population doubling time before and after the changes?

(A)Doubling time increases from about 25 years to about 50 years because the growth rate is cut in half.(B)Doubling time decreases from about 50 years to about 25 years because improved education increases infant mortality rates.(C)Doubling time remains about the same because carrying capacity determines doubling time, not growth rate.(D)Doubling time changes from about 2.5 years to about 5 years because the rule of 70 uses the growth rate as a decimal rather than a percent.

Refer to the figure below.

19. [Skill: 1.A | Topic: 3.9] [Image Cue]: Line graph, "Birth Rate and Death Rate Over Time (Country X)", x-axis = "Year" (1950, 1970, 1990, 2010), y-axis = "Rate (births or deaths per 1,000 people)". Two lines: Death rate decreases from ~30 (1950) to ~12 (1970) to ~8 (1990) to ~7 (2010). Birth rate stays high at ~40 (1950) and ~38 (1970) then declines to ~20 (1990) and ~12 (2010). The graph shows that Country X experienced a rapid decrease in death rate first, followed later by a decrease in birth rate as the country developed. Which of the following best defines the demographic transition illustrated by the data?

(A)A transition from high birth and death rates to lower birth and death rates as a country develops from a pre-industrial economy to an industrialized economy(B)A transition from low birth and death rates to higher birth and death rates as a country industrializes and urbanizes(C)A transition in which population size declines primarily because emigration increases as economic development occurs(D)A transition in which population growth stops when a population reaches carrying capacity due to limited resources

20. [Skill: 4.A | Topic: 3.9] A researcher compares two countries to infer which is more likely to be developing. Data: - Country A: infant mortality = 52 deaths per 1,000 live births; percent of children (ages 10–14) in the workforce = 18% - Country B: infant mortality = 4 deaths per 1,000 live births; percent of children (ages 10–14) in the workforce = 0.5% Based on the data and typical demographic patterns, which conclusion is best supported?

(A)Country A is more likely developing because it has higher infant mortality and a larger fraction of children in the workforce(B)Country A is more likely developed because it has a larger workforce, which indicates industrialization(C)Country B is more likely developing because low infant mortality indicates limited access to health care(D)Country B is more likely developing because fewer children in the workforce suggests families can afford to have more children

B. Short Answer Questions (1 Question)

Answer all parts of each question. Answers must be in essay form. Outlines or lists alone are not acceptable.

Question 21:

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