AP Environmental Science Unit 2: The Living World: Biodiversity Practice Exam

Assessment for Unit 2: The Living World: Biodiversity

Estimated Time: 60 minutes

Exam Details

Questions: 21 total (20 multiple choice, 1 short answer)
Time: 60 minutes (recommended)
Topics Covered: Unit 2: The Living World: Biodiversity
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.

1. [Skill: 4.A | Topic: 2.1] A wildlife agency monitored genetic diversity in a small island population of foxes before and after a severe wildfire reduced the population size. Data summary: - Estimated population size before wildfire: 1,200 foxes - Estimated population size after wildfire: 45 foxes - Average heterozygosity (a measure of genetic variation) before wildfire: 0.62 - Average heterozygosity after wildfire: 0.18 Which of the following best explains why the post-wildfire fox population is at greater risk of decline if a new disease is introduced?

(A)Lower genetic diversity reduces the likelihood that some individuals have resistance alleles, making the population less able to respond to the new stressor.(B)Lower genetic diversity increases the birth rate, causing the population to exceed carrying capacity and crash when the disease arrives.(C)Lower genetic diversity increases habitat diversity, which forces individuals into closer contact and increases transmission of disease.(D)Lower genetic diversity guarantees that natural selection will rapidly create new beneficial mutations to resist the disease.

Refer to the figure below.

2. [Skill: 4.B | Topic: 2.1] Ecologists compared two grassland plots after a drought. - Plot 1 contains 6 plant species. - Plot 2 contains 18 plant species. After the drought ended, scientists measured the percent recovery of plant biomass (compared with pre-drought biomass) for 12 months. [Image Cue]: Line graph, "Biomass Recovery After Drought", x-axis = Time after drought (months: 0, 3, 6, 9, 12), y-axis = Biomass recovery (% of pre-drought: 0 to 100). Plot 1 line increases slowly from 40% at month 0 to 65% at month 12. Plot 2 line increases more rapidly from 40% at month 0 to 90% at month 12. Which of the following conclusions is best supported by the data?

(A)The plot with greater species richness is more resilient because it recovers biomass more quickly after a disturbance.(B)The plot with lower species richness is more resilient because it has fewer species competing for limited resources.(C)Species richness describes the genetic diversity within a species, which explains the faster recovery in Plot 2.(D)The faster recovery in Plot 2 indicates it has lower habitat diversity than Plot 1.

3. [Skill: 1.A | Topic: 2.1] A region of continuous old-growth forest is fragmented by road building and housing development. Over time, the remaining forest patches become smaller and more isolated. Local species include: - A leaf-eating insect that can feed only on one native tree species - A raccoon that eats many different foods and can live near humans - A large carnivore that requires a very large territory to find enough prey According to ecological principles about habitat loss, which population is most likely to decline first as fragmentation increases?

(A)The raccoon, because generalist species typically decline before specialist species when habitat is lost.(B)The leaf-eating insect, because specialist species are typically lost first when habitat is reduced or altered.(C)The large carnivore, because species with large territorial requirements are always lost before all other species.(D)All three populations will increase at the same rate because fragmentation increases edge habitat and biodiversity.

4. [Skill: 1A | Topic: 2.2] A coastal city is considering conserving a nearby mangrove forest. A city report notes that during tropical storms, neighborhoods behind intact mangroves experience lower storm-surge heights and less shoreline erosion than neighborhoods where mangroves were removed. Which category of ecosystem service is best represented by the mangroves’ reduction of storm-surge damage and shoreline erosion?

(A)Provisioning service(B)Regulating service(C)Cultural service(D)Supporting service

5. [Skill: 4A | Topic: 2.2] A county converted 600 hectares of wetland to commercial development. Five years of county records are summarized below. Table 1. Selected annual impacts before vs. after wetland conversion - Average annual flood-damage costs: increased from 0.8 million dollars to 4.6 million dollars - Annual municipal drinking-water treatment costs: increased from 2.1 million dollars to 3.0 million dollars - Average number of days per year with beach-closure advisories from high bacteria levels: increased from 2 days to 14 days Which claim is best supported by the data regarding human disruption of ecosystem services?

(A)Wetland removal mainly reduces provisioning services, leading to higher costs for imported seafood.(B)Wetland removal disrupts regulating services, increasing both ecological impacts (poorer water quality) and economic costs (more flood damage and treatment expenses).(C)Wetland removal primarily disrupts cultural services, causing more beach closures but no measurable economic consequences.(D)Wetland removal increases supporting services, which raises flood-damage costs but improves drinking-water quality.

Refer to the figure below.

6. [Skill: 2B | Topic: 2.2] A farming region planted large areas of a single crop. Over three years, insecticide use increased substantially. Researchers measured wild pollinator abundance near fields and average crop yield. [Image Cue]: Line graph, "Pollinator Abundance and Crop Yield Over Time", x-axis = Year 1 to Year 3, left y-axis = Pollinator abundance index (drops from 100 in Year 1 to 55 in Year 3), right y-axis = Crop yield (tons per hectare) (drops from 4.2 in Year 1 to 3.1 in Year 3). Include a note on the figure: "Insecticide application rate increased each year." Based on the graph, which choice best identifies the ecosystem service being reduced and a likely consequence of its disruption?

(A)Provisioning service; increased crop yields because fewer insects consume the crop(B)Regulating service; decreased crop yields and reduced farm revenue due to reduced pollination(C)Cultural service; decreased crop yields because fewer tourists visit farmland(D)Supporting service; decreased crop yields because soil formation stops immediately when insecticides are applied

Refer to the figure below.

7. [Skill: 2A | Topic: 2.3] [Image Cue]: Line graph, "Island Biogeography Model: Immigration and Extinction Rates". x-axis: "Number of species present on island" (0 to 100). y-axis: "Rate" (low to high). Two downward-sloping immigration curves labeled "Near island" (higher) and "Far island" (lower). Two upward-sloping extinction curves labeled "Large island" (lower) and "Small island" (higher). The curves intersect at four equilibrium points. A student uses the graph to compare expected equilibrium species richness on islands that differ in distance from the mainland and in size. Based on the model, which island is expected to have the greatest equilibrium number of species?

(A)A small island close to the mainland(B)A large island close to the mainland(C)A small island far from the mainland(D)A large island far from the mainland

8. [Skill: 3A | Topic: 2.3] A biologist surveys four habitat "islands" (forest fragments) within an agricultural landscape. All fragments were formed at the same time and are similar in climate and habitat type. The table shows fragment area, distance to the nearest continuous forest (a source of colonists), and the number of bird species recorded after several years. Table: Forest fragments - Fragment 1: Area = 2 km^2; Distance = 1 km; Bird species = 18 - Fragment 2: Area = 2 km^2; Distance = 25 km; Bird species = 10 - Fragment 3: Area = 20 km^2; Distance = 1 km; Bird species = 42 - Fragment 4: Area = 20 km^2; Distance = 25 km; Bird species = 30 Which conclusion is most consistent with island biogeography and best supported by the data?

(A)Distance to the source habitat has no effect on colonization, because all fragments have the same habitat type.(B)Larger fragments tend to support more species because extinction rates are lower in larger areas.(C)Smaller fragments tend to support more species because they have more edge habitat for birds to nest in.(D)Farther fragments tend to support more species because isolation reduces competition among colonists.

9. [Skill: 1A | Topic: 2.3] On a remote oceanic island, a flightless insect species feeds almost exclusively on one native plant species and lays eggs only in that plant’s stems. A cargo ship accidentally introduces a generalist ant species that can eat many different foods, including the eggs and larvae of insects. Which statement best explains how island biogeography relates to the insect’s long-term survival and evolution on the island?

(A)Island populations are typically specialists due to limited resources, and the introduced generalist is likely to outcompete or prey on the specialist, reducing its survival.(B)Island populations are typically generalists due to frequent immigration, so the specialist insect will rapidly expand its niche and become a generalist.(C)Because the island is isolated, no new species can arrive, so the ant introduction will not persist and will quickly go extinct.(D)Specialists are more likely than generalists to invade new islands, so the insect will disperse to nearby islands and avoid competition.

Refer to the figure below.

10. [Skill: 4.A | Topic: 2.4] [Image Cue]: Line graph, "Performance of Species X vs. Temperature". X-axis: Temperature (°C) from 0 to 40. Y-axis: Performance (percent of maximum) from 0 to 100. Curve begins near 0% at 8°C, rises to ~100% at 20°C, then declines back to ~0% at 32°C. A researcher measures the performance of Species X across a range of temperatures and obtains the curve shown. Which of the following best identifies the ecological tolerance range for Species X for temperature, as indicated by the data?

(A)0°C to 40°C, because the organism was tested across that entire range(B)8°C to 32°C, because performance is above 0 within that interval(C)18°C to 22°C, because performance is highest only in that interval(D)20°C only, because the organism reaches maximum performance at that temperature

11. [Skill: 4.A | Topic: 2.4] The table shows survival of two individual fish (Individual A and Individual B) of the same species after 24 hours at different salinities. Salinity (ppt): 5 | 10 | 15 | 20 | 25 | 30 Individual A survival: 0% | 40% | 90% | 80% | 20% | 0% Individual B survival: 0% | 0% | 50% | 95% | 70% | 10% Which of the following conclusions is best supported by the data and most clearly reflects the concept of ecological tolerance?

(A)Ecological tolerance applies only to species, because individuals of the same species must have identical tolerance limits(B)Ecological tolerance can apply to individuals, because Individual A and Individual B have different salinity ranges associated with survival(C)Ecological tolerance describes only the optimal conditions, because both individuals survive best near 20 ppt(D)Ecological tolerance cannot include salinity, because salinity is a chemical factor rather than a physical factor

12. [Skill: 1.A | Topic: 2.4] A freshwater mussel species in a river experiences the following conditions: • Historical summer water temperature: 18–22°C • After a power plant begins discharging warmed water, summer temperature near the discharge pipe is 28–30°C. • Surveys show mussels are abundant upstream but absent within 2 km downstream of the discharge. Which statement best uses ecological tolerance to explain the observed distribution of the mussels?

(A)Mussels are absent downstream because they migrated away from the discharge to avoid competition with upstream mussels(B)Mussels are absent downstream because the downstream area is outside their temperature tolerance range, leading to injury or death(C)Mussels are absent downstream because temperature is not an environmental condition that can limit aquatic organisms(D)Mussels are absent downstream because ecological tolerance applies only at the ecosystem level, not to a species

Refer to the figure below.

13. **1. [Skill: 4 | Topic: 2.5]** A research team monitored vegetation greenness (NDVI) in a temperate forest for 8 years. The graph below shows NDVI over time. [Image Cue]: Line graph, "NDVI in a Temperate Forest Over 8 Years"; x-axis = Month (Year 1 Month 1 through Year 8 Month 12); y-axis = NDVI (0.0–0.9). Trend: repeating annual seasonal peaks each summer and lows each winter (periodic pattern), plus two sharp, one-month NDVI drops to near 0.1 in Year 3 late summer and Year 7 late summer followed by gradual recovery over ~12–18 months (episodic events). Which of the following best explains the pattern in the graph in terms of ecosystem disruptions?

(A)The repeating annual NDVI cycle reflects periodic Earth system processes (seasonality), while the two abrupt NDVI crashes are consistent with episodic disruptions such as wildfire or severe storms that can rapidly reduce primary productivity.(B)The abrupt NDVI crashes indicate a random Earth system process, and the annual NDVI cycle indicates episodic disruptions that occur unpredictably.(C)Both the annual cycle and the abrupt NDVI crashes reflect long-term geological processes that operate only over millions of years.(D)The NDVI pattern indicates that natural disruptions generally have smaller ecosystem consequences than human-made disruptions, because NDVI returns to previous values after each crash.

Refer to the figure below.

14. **2. [Skill: 4 | Topic: 2.5]** A geoscience class compares global sea level estimates and coastal habitat extent at three times in Earth’s recent history. [Image Cue]: Data table, "Glacial Ice, Sea Level, and Coastal Habitat" with columns: Time period; Global ice volume (relative units); Sea level relative to present (meters); Approx. exposed continental shelf area (million km^2). Rows: - Last Glacial Maximum (~20,000 years ago): ice volume high; sea level −120 m; exposed shelf area high. - Mid-interglacial (modern): ice volume moderate; sea level 0 m; exposed shelf area moderate. - Warmer-than-modern interglacial: ice volume low; sea level +6 m; exposed shelf area low. Which of the following best explains the relationship shown and its likely ecological consequence?

(A)When more water is stored as glacial ice, sea level falls, exposing more continental shelf; this can create large habitat shifts (e.g., expansion of land habitats and contraction/relocation of shallow coastal marine habitats).(B)When more water is stored as glacial ice, sea level rises, flooding continental shelves; this increases available land habitat area and decreases habitat change.(C)Sea level changes are primarily driven by short-term daily tidal cycles, so the habitat changes shown would be minor and localized.(D)Sea level has remained constant over geological time, so differences in exposed shelf area must be caused mainly by human coastal development.

15. **3. [Skill: 1 | Topic: 2.5]** A volcanic eruption on an oceanic island deposits ash over much of the island, killing many plants and reducing insect populations. Field biologists observe that within weeks, several bird species leave the ash-covered areas for nearby unimpacted islands. Over the next 30 years, as vegetation slowly recovers, some species re-establish breeding populations on the original island, while other species no longer breed there. Which of the following best explains the birds’ movement patterns?

(A)The rapid movement to nearby islands is short-term migration in response to a natural disruption that reduced food and habitat quality; the longer-term changes in which species breed on the island reflect large-scale habitat change that can alter community composition for decades.(B)The rapid movement to nearby islands is long-term migration driven primarily by seasonal temperature changes; the long-term absence of some species must be caused by daily tidal cycles.(C)The rapid movement is evidence that natural disruptions do not affect biodiversity because populations can always return immediately once the event ends.(D)The long-term absence of some breeding populations shows that only human-made disruptions cause lasting ecosystem change, whereas natural disruptions never produce long-lasting habitat effects.

Refer to the figure below.

16. [Skill: 2A | Topic: 2.6] [Image Cue]: Line graph, "Frequency of Dark (D) Allele in a Moth Population Over Time"; x-axis: Generation (0, 5, 10, 15, 20); y-axis: Frequency of D allele (0.0 to 1.0). Data trend: frequency starts at 0.10 in generation 0, rises steadily to 0.25 (gen 5), 0.45 (gen 10), 0.65 (gen 15), and 0.80 (gen 20). Brief caption: "In generation 2, soot deposition from nearby factories darkened tree bark; visual predators preferentially captured lighter moths." Which of the following best describes how the moth population adapted to the changed environment?

(A)Individual moths became darker during their lifetimes in response to soot, and they passed that acquired trait to offspring.(B)Natural selection increased the frequency of an existing dark-color allele because darker moths survived and reproduced more successfully after soot deposition.(C)The soot directly caused a mutation in most moths, converting the light-color allele into a dark-color allele within a single generation.(D)Random mating, independent of predation, caused the dark-color allele to increase because all phenotypes had equal survival and reproduction.

17. [Skill: 4A | Topic: 2.6] A student investigates whether a coastal grass population has adapted to rising soil salinity. The student collects seeds from two sites: - Site L (low salinity) - Site H (high salinity) The student grows both seed groups in a greenhouse under identical conditions (same light, nutrients, and watering), except that half of the plants from each site are grown in low-salinity soil and half in high-salinity soil. After 10 weeks, plants from Site H have higher survival than plants from Site L in high-salinity soil, and this pattern persists even though all plants were grown in the same greenhouse environment. Which conclusion is best supported by the results?

(A)Site H plants show evidence of an inherited trait that improves survival in high-salinity conditions, consistent with adaptation over generations.(B)Site H plants survived better because they became tolerant during the experiment and passed that tolerance to neighboring plants through the soil.(C)Soil salinity affects only short-term behavior, so differences in survival must be due to chance rather than environmental conditions.(D)The higher survival of Site H plants proves that the greenhouse conditions exactly replicated all environmental factors from Site H.

18. [Skill: 1A | Topic: 2.6] A species of alpine rabbit lives only on a single mountain range. Over the last 15 years, average summer temperature in the habitat increased by 2°C, reducing snow cover and increasing heat stress. Field surveys indicate the population has low genetic diversity and that the rabbits have a long generation time (about 6 years). The surrounding lowlands are warmer and fragmented by highways and development. Which outcome is most likely for the alpine rabbit population if warming continues at the same rate?

(A)Rapid evolutionary adaptation will occur within a few years because all individuals will adjust genetically to higher temperatures.(B)Migration to the surrounding lowlands will be the most likely response because the lowlands provide cooler habitat and easy dispersal corridors.(C)Local extinction is likely because the environmental change is relatively rapid compared with generation time and the population has limited genetic variation and limited dispersal options.(D)The rabbits will avoid heat stress permanently by changing daily behavior, eliminating any long-term risk from warming.

Refer to the figure below.

19. [Skill: 4.B | Topic: 2.7] A forested site was clear-cut in Year 0 and then left undisturbed. Ecologists measured total biomass, species richness, and net primary productivity (NPP) of the site over the next 80 years. [Image Cue]: Line graph, "Ecosystem Changes During Succession After Clear-Cutting". X-axis: Years since disturbance (0, 10, 20, 30, 40, 60, 80). Y-axis: Relative value (arbitrary units). Three curves: (1) Total biomass increases steadily and begins to level off after ~60 years; (2) Species richness increases rapidly from 0–30 years and then levels off; (3) NPP rises from 0–20 years, peaks around 20–30 years, then gradually declines by 80 years. Which of the following best explains the trends shown in the graph?

(A)As succession proceeds, biomass and species richness generally increase, while NPP often peaks during mid-succession and later declines as respiration increases in a mature community.(B)As succession proceeds, biomass decreases as larger organisms replace smaller ones, and NPP increases continuously as the community becomes more stable.(C)As succession proceeds, species richness declines because late-successional species outcompete all early-successional species, and NPP remains constant because producers always photosynthesize at the same rate.(D)The graph indicates that succession does not affect ecosystem properties; the observed patterns are random variation unrelated to disturbance recovery.

20. [Skill: 1.A | Topic: 2.7] Ecologists studied two sites and a nearby stream. Site 1: A new volcanic deposit created bare rock with no soil. The first organisms observed were lichens and cyanobacteria. Site 2: A pine forest experienced a wildfire that removed most vegetation but left the soil intact. Stream: In the stream draining the watershed, the researchers tracked mayfly nymph abundance over time because mayflies are sensitive to low dissolved oxygen and some pollutants. In Site 2, beavers repeatedly built dams that created ponds and wetlands, changing water flow and creating habitat for many additional species. Which of the following correctly identifies the type of succession and the ecological roles described?

(A)Site 1 is secondary succession; lichens are a keystone species; mayflies are pioneer species; beavers are indicator species.(B)Site 1 is primary succession; lichens are pioneer members of an early successional community; mayflies are an indicator species; beavers are a keystone species.(C)Site 2 is primary succession; lichens are indicator species; mayflies are keystone species; beavers are pioneer members of an early successional community.(D)Site 2 is secondary succession; lichens are late-successional species; mayflies are pioneer species; beavers are indicator species.

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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