AP Environmental Science The Living World: Biodiversity Guide
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The Living World: Biodiversity in the AP Environmental Science blueprint
College Board assigns Unit 2, The Living World: Biodiversity, 6–8% of AP Environmental Science multiple-choice questions. This range describes the multiple-choice section, not a percentage of the total exam score.
The Living World: Biodiversity
- May 2027
- Bluebook
- Clean-room teaching
- Read the evidence surface.
- Trace the environmental mechanism.
- Check units, scale, and claim scope.
What The Living World: Biodiversity covers
Within The Living World: Biodiversity, use these routes to connect official topics to evidence, calculations, and environmental decisions.
Unit 2: The Living World: Biodiversity
2.1 Introduction to Biodiversity
When studying The Living World: Biodiversity, biodiversity includes variation within species, among species, and among ecosystems and can increase resilience and option value.
2.2 Ecosystem Services
2.3 Island Biogeography
2.4 Ecological Tolerance
2.5 Natural Disruptions to Ecosystems
2.6 Adaptations
2.7 Ecological Succession
Vocabulary anchors
Introduction to Biodiversity; Ecosystem Services; Island Biogeography; Ecological Tolerance; Natural Disruptions to Ecosystems; Adaptations; Ecological Succession are the official topic anchors used throughout this unit. Species richness counts represented species, while species evenness describes their relative abundance distribution.
Evidence lab: Bird richness on four mangrove islands
Bird richness on four mangrove islands All islands were surveyed with equal effort. Distance is measured from the mainland. Island | Area (km²) | Distance (km) | Native bird species J | 1.2 | 2 | 18 K | 1.1 | 18 | 9 L | 8.4 | 3 | 31 M | 8.1 | 20 | 20
Which comparison most directly isolates the effect of distance?
J and K — Their areas are nearly equal while distance differs greatly.
Area and distance both differ. Both area and distance differ. Adding a third island does not isolate one variable as cleanly as the matched pair.
Identifies a matched comparison in one table.
Which pattern is consistent with island biogeography theory?
Larger and nearer islands support more species than comparable smaller or farther islands. — J versus K shows the distance pattern, and L versus J shows the area pattern at similar distance.
Matched-area islands differ strongly with distance. The larger islands have higher richness within similar distance classes. Survey effort was held equal.
Combines two controlled comparisons to evaluate a model.
A causeway is built from the mainland to Island K. Which mechanism could increase native richness?
Higher immigration can allow more mainland species to colonize K. — Connectivity lowers isolation and raises arrival probability.
Construction does not change island age. Connectivity does not remove local extinction risk. The immigration mechanism does not require changing ocean salinity.
Transfers the distance variable to the immigration mechanism.
Which result would most strongly challenge a simple area-distance explanation?
After repeated surveys, a small remote island has more native species than all larger near islands because it contains several unique habitat types. — The result identifies habitat heterogeneity as an omitted driver rather than mere sampling noise.
Small sampling variation does not overturn the broad pattern. That is consistent with higher immigration. More individuals can accompany the predicted richness pattern.
Requires identifying a model limitation supported by a specific counterpattern.
Managers can fund either a narrow causeway or restoration of three habitat types on K. What evidence is needed for the better biodiversity decision?
Estimate colonization gains and habitat-specific persistence under each option, including invasive-species risk from the causeway. — The choice requires comparable benefits, persistence, and an unintended connectivity cost.
Cost alone does not establish biodiversity effectiveness. Abundance at one time does not measure native richness or persistence. They act through different mechanisms and risks.
Integrates island theory, habitat heterogeneity, persistence, and invasion tradeoff.
Evidence lab: Vegetation after two disturbances
Vegetation after two disturbances Percent cover was measured five years after disturbance in nearby sites with the same climate. Site | Disturbance | Soil organic layer | Lichen cover (%) | Grass cover (%) | Shrub cover (%) P | lava flow | absent | 38 | 4 | 1 Q | wildfire | present | 3 | 47 | 26
Which site is undergoing primary succession?
Site P — New lava lacks a soil organic layer, so community development begins on newly exposed substrate.
The retained soil supports secondary succession. Succession type depends on whether soil remains. Pioneer organisms are expected during primary succession.
Classifies succession using the soil evidence.
Why is grass cover higher at Site Q?
Surviving soil, nutrients, and propagules allow faster recolonization after fire. — Secondary succession starts with biological legacies absent from fresh lava.
Fire may volatilize some nitrogen but does not remove the entire soil system. Fresh lava does not contain a preexisting root network. P has almost no shrubs and lacks developed soil.
Connects one observed difference to retained ecological legacies.
Which measurement after another five years would best quantify succession rate?
Repeat percent cover and species-composition surveys in permanent plots at both sites. — Permanent plots measure change through time using the same response variables.
One temperature reading does not quantify community change. Rock counts do not track vegetation succession. The photograph lacks a matched time series.
Selects a repeated response measure and fixed sampling units.
A student concludes that wildfire always increases biodiversity because Q has more plant cover. What is the main flaw?
Plant cover is not species diversity, and the comparison includes different disturbance types and starting substrates. — The conclusion changes the response variable and overgeneralizes a confounded comparison.
Five years can be informative; the issue is inference, not an absolute time ban. Lichens are living symbioses and valid community members. The measures use different units and are not compared that way.
Requires auditing response-variable substitution, confounding, and universal language.
To accelerate recovery at P without importing invasive plants, which plan is most defensible?
Test locally sourced pioneer inoculation in replicated plots and monitor native recruitment and erosion against untreated plots. — The plan targets early soil formation, controls provenance risk, and includes a causal comparison.
Fast growth does not address invasion risk. Preventing colonization works against recovery. One survivor does not establish community recovery or soil development.
Combines succession mechanism, provenance risk, replication, and multiple outcomes.
cattail
Their outflow concentrations differ.
Continue in the A+ teaching layer for the remaining evidence labs, figure, and final audit.
How the AP Environmental Science assesses The Living World: Biodiversity
| Item | Weight / count | What it means |
|---|---|---|
| Official topic denominator | 7 | |
| Multiple choice | 80 questions in 90 minutes | |
| Free response | 3 questions in 70 minutes | |
| Calculation credit | ||
| Administration | May 2027 |
Species-richness recovery
Read each question as it appears on the exam paper, choose your answer, then tap it to see the feedback.
Practice 1: Calculate species-richness recovery
A reserve's native bird species richness rises from 36 species to 45 species.
What is the percent increase in native bird species richness?
Select the best answer.
A. 45 − 36 = 9%
❌ Not quite 😭 The subtraction gives an increase of 9 species, not 9%. A percentage requires division by the original richness.
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B. (45 − 36) ÷ 45 × 100 = 20%
❌ Not quite 😭 This uses the final richness as the denominator. Percent increase is measured relative to the original value.
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C. (45 − 36) ÷ 36 × 100 = 25%
✅ Correct! 😊 The gain of 9 species is compared with the original 36 species. This directly gives the relative increase.
D. 36 ÷ 45 × 100 = 80%
❌ Not quite 😭 This calculates the original richness as a fraction of the final richness. It does not calculate the increase.
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Full explanation
- Step 1Find the increase: 45 − 36 = 9 species.
- Step 2Use the original richness, 36 species, as the denominator.
- Step 3Calculate 9 ÷ 36 × 100 = 25%.
Practice 2: Analyze mangrove-island bird richness
Equal-effort surveys found 18 native bird species on Island J, area 1.2 km² and 2 km from the mainland, and 9 species on Island K, area 1.1 km² and 18 km from the mainland.
Identify the best comparison for the effect of distance, explain the relevant island-biogeography mechanism, state one limitation, and identify evidence needed before building a causeway to Island K.
Show your work.
A. Compare J and K, link proximity to immigration, and evaluate colonization, persistence, and invasive-species risk before construction.
✅ Correct! 😊 The islands are nearly equal in area but differ greatly in distance. The response tests the expected mechanism and includes a major connectivity tradeoff.
B. Attribute all richness differences to island age and assume a causeway removes extinction risk.
❌ Not quite 😭 Island age is not supplied, and connectivity does not eliminate local extinction. The response ignores both the displayed distance contrast and new risks.
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C. Compare two islands that differ greatly in both area and distance, then credit distance alone.
❌ Not quite 😭 When both predictors change, area remains an alternative explanation. A near-matched-area pair isolates distance more cleanly.
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D. Build the causeway because one later abundance count will prove permanent biodiversity recovery.
❌ Not quite 😭 Abundance at one time is not native species richness or long-term persistence. The plan also omits invasive-species monitoring.
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Full explanation
- Step 1J and K have nearly equal areas, so their large distance difference provides the cleanest displayed comparison.
- Step 2Lower isolation can raise immigration and allow more mainland species to colonize a near island.
- Step 3Habitat types and other unreported features could still affect richness, so the comparison is not complete causal proof.
- Step 4Compare expected colonization and persistence with habitat restoration, while monitoring invasive-species risk from added connectivity.
Key terms for The Living World: Biodiversity
- Introduction to Biodiversity
- Ecosystem Services
- Island Biogeography
- Ecological Tolerance
- Natural Disruptions to Ecosystems
- Adaptations
- Ecological Succession
- Species richness
- The count of distinct species represented in a defined community, without incorporating their relative abundances into the value.
- Species evenness
- The degree to which individuals are distributed similarly among the species present in a defined community.
The Living World: Biodiversity FAQ
Which levels of biodiversity should I keep separate?
Genetic diversity concerns variation within a species, species diversity concerns richness and evenness, and ecosystem diversity concerns habitat variety. The prompt’s measured level determines which claim is defensible.
How does island size change the island-biogeography prediction?
Larger islands generally support more habitats and larger populations, reducing extinction risk. Isolation chiefly changes immigration, so size and distance must not be collapsed into one vague biodiversity effect.
Why is ecological tolerance different from adaptation?
Tolerance describes the range in which an organism can function now. Adaptation is a heritable population trait shaped across generations; an individual exposed to stress does not evolve during the experiment.
What distinguishes primary from secondary succession on an exam?
Primary succession begins where soil is absent, whereas secondary succession follows disturbance where soil remains. That starting substrate changes colonization, nutrient availability, and the likely rate of community recovery.
How can I evaluate whether a corridor will protect biodiversity?
Check whether it connects suitable habitat and supports gene flow, then consider disease, invasive-species spread, edge effects, and road mortality. A corridor is a hypothesis with measurable outcomes, not an automatic benefit.
Continue through the APES system
How to study The Living World: Biodiversity
Sort biodiversity evidence by level before answering: genetic variation, species richness or evenness, and ecosystem variety. Add island area, isolation, disturbance history, and habitat quality only when the displayed study actually measures them.
Rehearse disturbance scenarios on a timeline. Mark the substrate present immediately afterward, the colonists that can arrive, changes in soil and light, and the community property measured. This makes primary versus secondary succession a mechanism rather than a label.
When evaluating conservation, write a two-column ledger of benefit and new risk. Corridors, predator removal, captive breeding, and protected areas each require a measurable success criterion plus monitoring for disease, edge effects, or displaced pressure.
