AP Biology: Invasive Species and Community Change Practice Questions
Practice invasive-species ecology with original AP Biology multiple-choice questions. These items focus on evidence, experimental design, mechanisms of spread, and how changing interactions can affect communities.
Free original practice questions for study purposes. Open Exam Prep is an independent study resource and is not affiliated with, endorsed by, or sponsored by the makers of AP Exams.
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1. A plant is moved by people to a region outside its historical range. It establishes self-sustaining populations, spreads into natural habitats, and reduces native seedling survival. Which term best describes the plant in the new region?
Explanation. An invasive species is a nonnative organism that establishes, spreads, and causes ecological, economic, or other harm. Being transported outside a historical range alone does not establish invasiveness; the documented spread and negative effect support the term.
2. Which observation would provide the strongest evidence that an introduced snail, rather than a drought, caused a decline in a native aquatic plant?
Explanation. Comparing replicated, similar lakes while accounting for water level helps separate the snail's association from drought effects. A single observation or shared location cannot distinguish competing explanations.
3. A nonnative grass produces many seeds that remain viable in soil for years and germinate quickly after fire. Which feature most directly promotes rapid population increase after a fire?
Explanation. A persistent seed bank can provide a large local source of propagules after disturbance, allowing rapid establishment in newly available space. It does not guarantee exclusion or remove ecological limits.
4. An introduced predator eats a native herbivore. After the predator becomes common, a native shrub increases in abundance. Which mechanism most directly explains the shrub increase?
Explanation. If the introduced predator reduces the herbivore population, less grazing can allow the shrub to increase. This is an indirect effect transmitted through a food-web interaction.
5. Researchers place equal numbers of native seedlings into replicated plots. Half the plots have an introduced plant removed repeatedly; the others are left unchanged. After one growing season, seedlings survive better in removal plots. What conclusion is best supported?
Explanation. The replicated removal experiment supports a causal effect of the introduced plant on seedling survival in the studied setting. Its result does not justify universal claims or rule out every other ecological factor.
6. Why can a small number of newly introduced individuals sometimes establish a population more easily when introductions occur repeatedly over several years?
Explanation. Propagule pressure refers to the number and frequency of arriving individuals. More introductions can increase the chance of establishment despite early mortality or chance events, though establishment is not guaranteed.
7. A native pollinator visits flowers of both a native plant and an introduced plant. The introduced plant produces much more nectar and receives most visits during its bloom. Which outcome is a plausible concern for the native plant?
Explanation. Shared pollinators can create an indirect interaction. If pollinators preferentially visit the introduced plant during overlapping flowering periods, the native plant may receive fewer visits and potentially lower pollination success.
8. An invasive insect kills a dominant canopy tree. Light reaches the forest floor, and shade-intolerant plants become more abundant. Which statement best describes this change?
Explanation. Removing a dominant canopy tree changes light availability, an abiotic condition. Species adapted to brighter conditions can then become more abundant, producing a community-level change.
9. Which result would best indicate that a native community has biotic resistance to an introduced plant?
Explanation. Biotic resistance occurs when interactions in the resident community, such as competition, herbivory, or pathogens, limit the establishment or spread of a newcomer. Lower survival in intact vegetation is evidence consistent with that resistance.
10. Two ponds have the same initial abundance of a nonnative fish. Pond A has many connected waterways, while Pond B is isolated. Assuming similar habitat quality, why might the fish spread through Pond A's region more quickly?
Explanation. Landscape connectivity can increase dispersal among suitable patches, allowing an introduced population to colonize additional habitats. Connectivity does not eliminate evolution or density-dependent interactions.
11. A restoration team removes an invasive vine from one forest edge but leaves it in another similar edge. Native seedling richness rises only at the removal edge over three years. What is the most appropriate interpretation?
Explanation. Using a comparable untreated edge strengthens the inference that removal contributed to the observed richness increase. Natural variation may still occur, so the result should be interpreted within the study's conditions.
12. Which monitoring plan would most directly test whether an introduced mussel changes water clarity in a lake?
Explanation. Repeated measurements across comparable invaded and uninvaded sites provide stronger evidence about the relationship between mussel abundance and water clarity than a single observation. This design also helps reveal whether changes persist through time.
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FAQ
What makes a species invasive?
In ecology, an invasive species is generally nonnative to the region, establishes and spreads, and causes harm. Not every introduced species becomes invasive.
How can invasive species change a community?
They can alter competition, predation, herbivory, mutualisms, resource availability, disturbance patterns, or physical conditions. The outcome depends on the species and ecosystem.
Why are control plots useful in invasive-species studies?
Control plots provide a comparison that helps distinguish effects linked to an introduced species or its removal from background environmental variation.