Introduction to Biodiversity - AP Environmental Science

1. A conservation team compares two regions. Region 1 contains one large intact mangrove ecosystem. Region 2 contains mangroves, seagrass beds, coral reefs, and salt marshes. Which biodiversity level is higher in Region 2, and what is a key benefit of that higher level?
   Answer: Ecosystem diversity; it supports a wider range of ecological processes and services Ecosystem diversity refers to the variety of distinct ecosystems in an area, such as mangroves, seagrass beds, coral reefs, and salt marshes in Region 2, compared to just one in Region 1. This level is higher in Region 2 and is important because it supports a wider range of ecological processes and services, like nutrient cycling, coastal protection, and habitat provision for diverse species. The benefit arises from increased resilience, as different ecosystems can provide complementary functions and buffer against disturbances affecting any single one. Genetic diversity involves variation within species, not ecosystem types, while species diversity counts species but doesn't capture habitat variety. Prioritizing ecosystem diversity in conservation can enhance overall biodiversity by fostering niches for more species and maintaining functional redundancy. This concept underscores why regions with multiple ecosystems are often hotspots for broader biodiversity protection.
2. A restoration project replants a degraded hillside with a single fast-growing tree species. Tree survival is high, but few insects and birds return. Which biodiversity limitation is most evident in this restoration approach?
   Answer: Low species diversity, which can limit habitat and food resources for many organisms Low species diversity from planting only one tree species limits habitat and food resources, explaining why few insects and birds return despite high tree survival, as diverse species provide varied niches. This highlights species diversity's importance in supporting broader biodiversity and ecosystem function. Ecosystem diversity isn't low due to too many; it's the monoculture issue. Genetic diversity isn't the primary limitation here. Endemism doesn't prevent recolonization. Restoration should incorporate species diversity for success.
3. A wildlife manager wants to increase the genetic diversity of an isolated wolf population. Which action most directly targets genetic diversity rather than species or ecosystem diversity?
   Answer: Introduce individuals from a different wolf population to increase gene flow Genetic diversity within the wolf population can be increased by introducing individuals from another population, promoting gene flow and reducing inbreeding, directly targeting allelic variation. Other actions like habitat conversion or reintroducing predators address ecosystem or species diversity, not genetics. This distinction is important for tailored conservation strategies. Genetic diversity enhances adaptability and population viability. Ecosystem diversity involves habitat types, species diversity adds organisms. Effective management often requires addressing specific biodiversity levels.
4. A researcher samples DNA from 50 individuals of the same butterfly species in two meadows. Meadow 1 shows 20 haplotypes; Meadow 2 shows 5 haplotypes. What does this most directly indicate?
   Answer: Meadow 1 has higher genetic diversity within the butterfly species Genetic diversity within a species is measured by variations like haplotypes, which indicate allelic diversity and potential for adaptation. More haplotypes in Meadow 1 suggest higher genetic variation in the butterfly population there, possibly due to larger size or less isolation. This level of biodiversity is important for resilience to environmental changes. Species diversity would compare different species, not haplotypes within one. Ecosystem diversity involves habitat variety, not genetic metrics. Choice A is correct as it directly ties haplotypes to genetic diversity within the species, distinguishing it from other levels.
5. A city plans to replace a vacant lot with a single-species lawn (one grass species) instead of a mixed native planting (20 native plant species). City ecologists argue the mixed planting will better support pollinators and stabilize food webs. Which statement best describes the biodiversity-related reasoning behind the ecologists' argument?
   Answer: Higher species diversity can increase ecosystem resilience and provide more niches and food resources for pollinators Species diversity in plant communities directly impacts ecosystem function and the organisms they support. The mixed native planting with 20 species provides multiple benefits over a single-species lawn. Higher plant diversity creates more ecological niches - different flower shapes, blooming times, and nectar resources - supporting a wider variety of pollinator species throughout the season. This diversity also increases ecosystem resilience; if one plant species fails due to disease or weather, others can compensate, maintaining food resources for pollinators. Additionally, diverse plant communities often have more complex food webs and habitat structure, supporting not just pollinators but their predators and parasites. The single-species lawn offers limited resources and timing, creating a less stable and supportive environment for pollinator communities.
6. Scientists track biodiversity in a river basin by recording (1) number of fish species, (2) allele frequencies in one trout species, and (3) number of distinct habitat types (riffles, pools, wetlands, floodplain forests). Which pairing correctly matches each measurement to a biodiversity level?
   Answer: (1) species, (2) genetic, (3) ecosystem Biodiversity levels include species (variety of organisms), genetic (variation within species), and ecosystem (habitat diversity). Here, (1) number of fish species measures species diversity, (2) allele frequencies in trout measure genetic diversity, and (3) habitat types like riffles and pools measure ecosystem diversity. This matching is correct and shows how different metrics capture distinct aspects of biodiversity. Species diversity informs community complexity, genetic diversity affects adaptation, and ecosystem diversity supports varied processes. Accurate labeling is essential for comprehensive monitoring. Integrating these levels provides a fuller picture of river basin health.
7. A government report states: "The country's biodiversity is declining." The data show (i) the number of forest ecosystem types has stayed constant, (ii) the number of bird species recorded nationwide has stayed constant, but (iii) several bird populations have become very small and isolated, with reduced gene flow among them. Which level of biodiversity is most clearly declining according to the report's data?
   Answer: Genetic diversity, because small isolated populations tend to lose variation through drift and inbreeding The report presents data on all three levels of biodiversity: ecosystem diversity (forest types), species diversity (bird species numbers), and genetic diversity (gene flow and population connectivity). The data shows ecosystem diversity is stable (constant forest types) and species diversity appears stable (constant bird species numbers). However, the critical finding is that bird populations have become small and isolated with reduced gene flow. This isolation leads to genetic drift and inbreeding, reducing genetic variation within populations. Small populations lose alleles randomly and cannot maintain the genetic diversity needed for adaptation. The clear decline is in genetic diversity - while the same species exist, they're losing the genetic variation within populations that ensures long-term survival and adaptability.
8. A coral reef and a kelp forest both occur along the same coastline. After a marine heatwave, the coral reef shifts to algae dominance while the kelp forest remains stable. Which biodiversity concept best explains why maintaining multiple ecosystem types in a region can be valuable?
   Answer: Higher ecosystem diversity can buffer regional ecosystem services because different ecosystems respond differently to disturbances Ecosystem diversity, with multiple types like coral reefs and kelp forests, provides value by buffering regional services, as different ecosystems respond variably to disturbances like heatwaves, maintaining overall function. This concept illustrates resilience through diversity at the ecosystem level. Genetic diversity doesn't prevent state changes, and richness doesn't guarantee uniform responses. Endemism isn't relevant here. Maintaining ecosystem variety enhances regional stability. This is key in climate adaptation planning.
9. A grassland has 20 plant species. A second grassland has 10 plant species but includes two rare nitrogen-fixing species that strongly influence soil fertility and support many insects. Which statement best evaluates biodiversity importance?
   Answer: The second grassland may be highly important because certain species can disproportionately support ecosystem function Species diversity includes not just richness (number of species) but also the roles species play, such as keystone species that disproportionately affect ecosystems. In the second grassland, the nitrogen-fixing plants enhance soil fertility, supporting insects and overall productivity, which underscores their functional importance. This shows that biodiversity importance extends beyond mere counts to how species contribute to ecosystem services like nutrient cycling. Evaluating biodiversity should consider ecological impacts, where low-richness areas with key species can be highly valuable. The first grassland's higher richness is beneficial, but it doesn't automatically outweigh the functional roles in the second. Choice B is correct because it recognizes the disproportionate ecosystem support from certain species, highlighting why the second grassland may be important despite fewer species.
10. A botanist samples two meadows of equal size. - Meadow A: 10 plant species, all native, with similar abundances. - Meadow B: 15 plant species, but 1 invasive grass makes up 90% of all plants. Which meadow likely has higher functional stability and why (based on biodiversity concepts)?
    Answer: Meadow A, because higher evenness can support more balanced interactions and resilience Functional stability in ecosystems often relates to species diversity, where higher evenness, as in Meadow A with 10 native species of similar abundances, can support balanced interactions, redundancy, and resilience to disturbances. Meadow B's higher richness is undermined by dominance of one invasive grass, potentially reducing stability due to over-reliance on a single species. This illustrates how evenness complements richness in biodiversity's role in ecosystem function. Invasives can decrease native diversity, not increase genetic diversity. Ecosystem count isn't relevant here. Prioritizing evenness in restoration enhances long-term meadow health.
11. A mountainous tropical region is labeled a biodiversity hotspot. Which combination of characteristics best matches the typical criteria used for hotspots?
    Answer: High endemism and high levels of habitat loss or threat Biodiversity hotspots are regions with exceptional concentrations of endemic species facing high levels of habitat destruction, aimed at prioritizing conservation where losses would be irreplaceable. Endemism means species are found nowhere else, so their extinction equates to global loss. High threat levels, like habitat loss, amplify the urgency in tropical mountains, which often have diverse microhabitats fostering unique species. This designation helps focus limited resources on areas that maximize biodiversity preservation. Primary productivity or human population aren't core criteria; it's about endemism and risk. Choice B is correct as it matches standard hotspot criteria from organizations like Conservation International, emphasizing endemism and threats over other mismatched factors.
12. A scientist measures biodiversity in three ways: (i) number of bird species, (ii) number of forest types (old-growth, secondary, plantation), and (iii) number of unique alleles in a keystone tree species. Which option correctly labels (i), (ii), and (iii)?
    Answer: (i) species diversity, (ii) ecosystem diversity, (iii) genetic diversity The measurements correspond to (i) species diversity (bird species count), (ii) ecosystem diversity (forest types), and (iii) genetic diversity (alleles in a tree species), capturing different biodiversity scales. Species diversity reflects community variety, ecosystem diversity habitat range, and genetic diversity adaptive potential. Correct labeling ensures accurate biodiversity assessment. These levels interconnect, with ecosystems supporting species and genetics enabling evolution. Integrated monitoring informs conservation. This approach reveals comprehensive ecosystem insights.
13. In a hotspot region, conservationists debate protecting either (i) a small area with extremely high plant endemism or (ii) a larger area with more total species but fewer endemics. Which additional information would be most useful for deciding based on hotspot logic?
    Answer: The degree of threat (rate of habitat loss) and how many endemic species would be secured by protection Hotspot logic prioritizes areas with high endemism and imminent threats, as these maximize the prevention of global extinctions per conservation effort. Degree of threat, like habitat loss rate, and the number of endemics protected are crucial for decision-making. This ensures resources target irreplaceable biodiversity under pressure. Size and total species are factors, but endemism and threat are core. Plant height or tree age don't relate to biodiversity metrics. Choice B is correct by focusing on threat and endemism, aligning with hotspot criteria over irrelevant physical or geographic measures.
14. A city plans to replace a vacant lot containing native grasses, shrubs, insects, and several bird species with a single-species lawn (one grass cultivar). The city argues that "green space is green space." Which outcome best reflects the likely biodiversity change across levels?
    Answer: Species diversity and genetic diversity likely decrease because a monoculture lawn supports fewer species and has low within-species variation compared with a mixed native community. Converting a diverse native plant community to a monoculture lawn dramatically reduces biodiversity at multiple levels. Species diversity decreases because the varied native grasses, shrubs, insects, and birds are replaced by a single grass species, eliminating both species richness and evenness. Genetic diversity also declines because a single cultivar represents minimal genetic variation compared to the natural genetic variation within multiple native species. The native community's structural complexity and varied microhabitats support more species and ecological interactions than a uniform lawn. This example illustrates how human land use decisions can significantly impact biodiversity, even when maintaining "green space." The ecological value of diverse native communities far exceeds that of simplified, managed landscapes.
15. A national biodiversity report lists: 5 major biomes, 2,400 native species, and declining genetic variation in several crop wild relatives. Which statement best describes how these metrics relate to biodiversity?
    Answer: Biomes reflect ecosystem diversity; native species counts reflect species diversity; genetic variation reflects genetic diversity The report's metrics relate to biodiversity levels: biomes reflect ecosystem diversity (habitat variety), native species counts reflect species diversity (organism variety), and genetic variation in crops reflects genetic diversity (within-species variation). This comprehensive view shows how levels interconnect for overall biodiversity. Species counts aren't the only measure; all contribute. Genetic and ecosystem diversity differ despite environmental ties. Such reports guide national conservation policies. Understanding these aids in addressing biodiversity loss holistically.
16. Two populations of the same frog species (Population X in a wetland and Population Y in a nearby forest pond) are tested for genetic variation at 20 DNA loci. Population X has 3 alleles per locus on average, while Population Y has 8 alleles per locus on average. Which statement best identifies the biodiversity level being measured and why it matters for conservation planning?
    Answer: Genetic diversity; it matters because higher within-species variation can increase a population's ability to adapt to environmental change. This question measures genetic diversity, which refers to the variety of genes and alleles within a species. The measurement of alleles per locus directly assesses genetic variation within each frog population. Population Y has much higher genetic diversity (8 alleles per locus) compared to Population X (3 alleles per locus). This matters for conservation because populations with higher genetic diversity have more raw material for natural selection to act upon, increasing their ability to adapt to environmental changes like climate shifts, new diseases, or habitat alterations. Genetic diversity is one of the three main levels of biodiversity, distinct from species diversity (variety of species) and ecosystem diversity (variety of habitats).
17. A city plans to replace a mixed native woodland with a monoculture lawn and a few ornamental trees. Which biodiversity change is most likely?
    Answer: Species diversity will likely decrease because fewer niches and resources remain for native organisms Species diversity measures the variety and abundance of species in an area, which supports ecosystem resilience and services like pollination and nutrient cycling. Replacing diverse native woodland with a monoculture lawn simplifies habitats, reducing niches for native species and likely causing declines in species richness and evenness. This change diminishes biodiversity by favoring generalists over specialists adapted to woodlands. Ecosystem diversity also suffers as the area shifts from a complex forest to a uniform lawn. The importance of maintaining diverse habitats is to prevent such losses and sustain ecological functions. Choice A is correct because it predicts a decrease in species diversity due to fewer resources, accurately reflecting the impact unlike optimistic or incorrect alternatives.
18. A region contains three adjacent areas: (1) a desert scrub, (2) a montane conifer forest, and (3) an alpine meadow. A proposed highway would fragment the forest and meadow, but not the desert. Ecologists are concerned that fragmentation will reduce biodiversity at multiple levels. Which combination best describes the likely impacts?
    Answer: Genetic diversity within some forest/meadow species may decline due to reduced gene flow, and species diversity may decline if populations become locally extinct Habitat fragmentation impacts biodiversity at multiple levels simultaneously. At the genetic level, fragmenting the forest and meadow creates isolated populations with reduced gene flow between fragments, leading to loss of genetic diversity through drift and inbreeding. At the species level, fragmentation can cause local extinctions as some species require minimum habitat sizes or cannot cross the highway barrier, reducing species diversity in fragments. Small fragments may not support viable populations of area-sensitive species. While the highway doesn't create a new natural ecosystem or increase ecosystem diversity, it does alter the landscape structure. The desert remains unfragmented, but the forest and meadow communities face both genetic isolation within species and potential species loss, demonstrating how human infrastructure can degrade multiple levels of biodiversity simultaneously.
19. Two rainforest reserves are evaluated using a rapid assessment. - Reserve M: 300 tree species; 60 are endemic; deforestation rate in surrounding area is high - Reserve N: 450 tree species; 5 are endemic; surrounding area is stable Which metric combination most strongly aligns with identifying a biodiversity hotspot and why?
    Answer: High endemism and high threat, because hotspots prioritize unique species at high risk of extinction. Biodiversity hotspots are defined by two essential criteria: high endemism (species found nowhere else) and high threat level (typically measured by habitat loss). These criteria ensure conservation efforts focus on areas where unique biodiversity faces the greatest risk of extinction. Reserve M exemplifies a hotspot with 60 endemic species (20% endemism) and high surrounding deforestation, while Reserve N has minimal endemism despite more total species. The hotspot concept recognizes that preventing extinctions of endemic species is a conservation priority because once lost, these species cannot be recovered from other locations. High threat levels indicate urgency for conservation action before irreversible biodiversity loss occurs.
20. A conservation NGO wants a single metric to communicate biodiversity loss over time in a grassland. Which option best captures change in species diversity beyond just richness?
    Answer: Use a diversity index (e.g., Shannon index) that incorporates both richness and evenness Species diversity metrics like the Shannon index incorporate both richness and evenness, providing a comprehensive measure of change over time beyond just counting species. This is useful for communicating biodiversity loss, as it captures shifts in dominance. Biodiversity monitoring is important for tracking ecosystem health and guiding conservation. Tracking tallest plants or soil pH measures other aspects, not diversity. Ecosystem count isn't species-focused. Choice B is correct as it recommends a suitable index for species diversity, fitting the NGO's goal.

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