Biology Test Biology Ecology & Environmental Interactions 3 — Questions and Answers
Question 1: Eutrophication of a lake is most directly caused by
- Increased predation by invasive fish species
- Excess nutrient runoff stimulating algal blooms (Correct answer)
- A decrease in water temperature
- Introduction of filter-feeding organisms
Correct answer: Excess nutrient runoff stimulating algal blooms
Excess nitrogen and phosphorus from agricultural runoff cause algal blooms; when algae die, decomposition depletes oxygen, creating dead zones.
Question 2: Which of the following is an example of a density-dependent limiting factor?
- A volcanic eruption destroying habitat
- A severe drought killing vegetation
- Disease spreading more rapidly in a crowded population (Correct answer)
- A sudden frost killing organisms regardless of population size
Correct answer: Disease spreading more rapidly in a crowded population
Density-dependent factors like disease, predation, and competition intensify as population density increases.
Question 3: In an ecological pyramid of biomass, which level always has the greatest biomass?
- Top carnivores
- Secondary consumers
- Primary consumers
- Producers (Correct answer)
Correct answer: Producers
Producers (plants) form the base of the biomass pyramid because energy and mass decrease at each successive trophic level.
Question 4: Which relationship exists between clownfish and sea anemones, where both organisms benefit?
- Parasitism
- Commensalism
- Mutualism (Correct answer)
- Competition
Correct answer: Mutualism
Clownfish gain protection from the anemone's stinging tentacles, while the fish's movement aerates the anemone and removes parasites — a mutualistic relationship.
Question 5: The reintroduction of wolves to Yellowstone National Park caused changes that eventually led to stabilization of riverbanks through a process called
- Competitive exclusion
- A trophic cascade (Correct answer)
- Ecological succession
- Carrying capacity regulation
Correct answer: A trophic cascade
Wolves reduced elk overgrazing of vegetation near rivers, allowing plants to regrow and stabilize banks — a classic trophic cascade effect.
Question 6: Which process in the carbon cycle involves the release of CO2 from the burning of ancient organic matter?
- Photosynthesis
- Transpiration
- Combustion of fossil fuels (Correct answer)
- Nitrogen fixation
Correct answer: Combustion of fossil fuels
Burning fossil fuels releases carbon stored over millions of years back into the atmosphere as CO2, disrupting the natural carbon cycle.
Question 7: Resource partitioning among competing species in the same habitat is an example of
- Competitive exclusion
- Character displacement reducing direct competition (Correct answer)
- Niche overlap maximization
- Allopatric speciation
Correct answer: Character displacement reducing direct competition
Character displacement occurs when competing species evolve different traits to use different resources, reducing direct competition and allowing coexistence.
Biology Test Biology Ecology & Environmental Interactions 3
Eutrophication of a lake is most directly caused by