AP Environmental Science The Living World: Biodiversity Guide
Return to the AP Environmental Science exam guide.
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
The Living World: Biodiversity focus: Use these routes to connect official topics to evidence, calculations, and environmental decisions.
Unit 2: The Living World: Biodiversity
2.1 Introduction to Biodiversity
The Living World: Biodiversity focus: Biodiversity includes variation within species, among species, and among ecosystems and can increase resilience and option value.
2.2 Ecosystem Services
The Living World: Biodiversity focus: Ecosystem services are benefits people receive from natural systems, including provisioning, regulating, cultural, and supporting functions.
2.3 Island Biogeography
The Living World: Biodiversity focus: Island species richness reflects a balance between immigration and extinction that varies with island size and isolation.
2.4 Ecological Tolerance
The Living World: Biodiversity focus: Ecological tolerance is the range of environmental conditions within which an organism can survive, grow, and reproduce.
2.5 Natural Disruptions to Ecosystems
The Living World: Biodiversity focus: Natural disturbances can remove organisms or alter resources, creating selection pressures and opportunities for succession.
2.6 Adaptations
The Living World: Biodiversity focus: An adaptation is a heritable trait that increases reproductive success in a particular environment over generations.
2.7 Ecological Succession
The Living World: Biodiversity focus: Ecological succession is directional community change after disturbance; primary succession begins without soil, whereas secondary succession retains soil.
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.
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
The Living World: Biodiversity focus: Use this contract to connect unit study to the current APES exam.
| Item | Weight / count | What it means |
|---|---|---|
| Official topic denominator | 7 | The Living World: Biodiversity focus: Every listed CED topic is taught on this page and remains owned by one frozen taxonomy leaf. |
| Multiple choice | 80 questions in 90 minutes | The Living World: Biodiversity focus: The section includes discrete and shared-stimulus sets using models, data, maps, calculations, and text sources. |
| Free response | 3 questions in 70 minutes | The Living World: Biodiversity focus: The task families are investigation design, quantitative-data analysis, and an environmental problem with calculations. |
| Calculation credit | The Living World: Biodiversity focus: Setup and answer can be separate rubric lines | The Living World: Biodiversity focus: Write the model, substitute with units, and preserve a reasonable final magnitude. |
| Administration | May 2027 | The Living World: Biodiversity focus: This page is scoped to the current fully digital Bluebook administration and dated public facts. |
Species-richness recovery
- Step 1Use the original richness as the denominator: (45 − 36) / 36 × 100.
- Step 2The increase is 9 species, and 9 / 36 = 0.25.
- Step 3Therefore the relative increase is 25%; 20% incorrectly uses the final value as denominator.
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.
