Contemporary Issues in Biology Exam 3 Sawey, TCU (2026) -
150 Questions
This exam assesses advanced understanding of the interactions between climate change and biodiversity,
including species responses, ecosystem dynamics, conservation strategies, and policy implications. It emphasizes
quantitative reasoning, synthesis of recent literature, and application to real-world scenarios. It contains 150
multiple-choice questions, each with four distractors and a fully worked rationale that explains why the keyed
answer is correct. Content is organized into 10 focused sections: Climate Change and Biodiversity, Genetically
Modified Organisms (GMOs), Emerging Infectious Diseases, CRISPR and Gene Editing Ethics, Human
Population Growth and Sustainability, Conservation Biology and Endangered Species, Stem Cell Research and
Regenerative Medicine, Antibiotic Resistance, Personalized Medicine and Genomics, Environmental Pollution and
Human Health. Targeted learning outcomes include: Evaluate the mechanisms by which climate change drives
biodiversity loss; Analyze species' adaptive responses and extinction risks under different climate scenarios;
Critically assess conservation interventions and their effectiveness in mitigating climate impacts; Interpret climate
and biodiversity data from multiple sources. Every item has been reviewed for clinical accuracy, current
guidelines, and clarity so that students can study with confidence and self-correct as they work through the bank.
Use it as a high-yield review immediately before the exam, or as a structured practice tool during the unit - the
rationales double as concise teaching notes. The recommended writing time is 3 hours, with a passing score of
Section 1: Climate Change and Biodiversity (Questions 1-15)
1 A study of tropical montane bird communities along an elevational gradient from
1000 to 3000 m finds that over the past 20 years, the mean elevation of bird
abundances has shifted upward by an average of 35 m per decade. However, the
rate of upward shift varies among species: insectivores shift faster than frugivores,
and species with smaller body sizes shift faster than larger ones. Which of the
following best explains the observed variation in shift rates?
A) Insectivores are more sensitive to temperature increases than frugivores due to
higher metabolic rates.
B) Larger-bodied species have greater dispersal capabilities and can track climate
more effectively.
C) Frugivores depend on fruit availability, which may be more constrained by
photoperiod than temperature, slowing their range shifts.
D) Smaller species have shorter generation times, allowing faster evolutionary
adaptation to new thermal regimes.
Answer: C
Rationale: Frugivores rely on fruit resources that are often triggered by photoperiod,
not temperature alone, so their resource availability may not shift as quickly as
temperature isotherms. Insectivores, feeding on temperature-sensitive insects, track
climate more directly. Body size and generation time are less directly linked to shift
rate; dispersal ability (often higher in larger species) would predict faster shifts,
opposite to the observation.
,2 In a study of coral reef ecosystems, researchers measured net primary production
(NPP) and calcification rates across a gradient of ocean acidification (OA) and
warming. They found that at pCO levels of 800 atm and temperature 2°C above
current, NPP increased by 15% but calcification decreased by 40%. Based on
these findings, what is the most likely net effect on the reef's ability to maintain
positive net ecosystem calcification (NEC) under projected end-of-century
conditions?
A) NEC will increase because higher NPP provides more organic matrix for
calcification.
B) NEC will decrease because the decline in calcification outweighs the increase
in NPP.
C) NEC will remain stable because increased photosynthesis buffers pH and
promotes calcification.
D) NEC will become negative, causing net erosion, because the decline in
calcification is greater than the increase in NPP can compensate.
Answer: D
Rationale: Net ecosystem calcification is the balance between gross calcification and
dissolution. A 40% decrease in calcification is substantial, and while NPP increases,
the organic matter produced does not directly contribute to calcification and may
even enhance dissolution via respiration. Thus, NEC likely becomes negative,
leading to net erosion. The pH buffering from increased photosynthesis is
insufficient to offset the direct effects of OA on calcification.
3 A conservation biologist is evaluating the effectiveness of assisted colonization
for a tree species (Pinus albicaulis) whose current habitat is projected to become
climatically unsuitable by 2080. The species has a generation time of 30 years and
low seed dispersal distance. The target site is 200 km north of the current range,
but the soil mycorrhizal community differs. Which of the following additional
considerations would most strongly argue against proceeding with assisted
colonization?
A) The target site has 20% lower annual precipitation than the current site.
B) The target site currently hosts a different species of pine that is competitively
superior.
C) The target site lacks the specific ectomycorrhizal fungi required by P. albicaulis,
and inoculation trials show low survival.
D) The target site is within the current range of a native herbivore that feeds on
pine seedlings.
,Answer: C
Rationale: Assisted colonization success critically depends on mutualistic
interactions. Without the appropriate mycorrhizal symbionts, the tree cannot obtain
sufficient nutrients, leading to high mortality. While precipitation and competition
are important, they can sometimes be mitigated or are less immediately lethal.
Herbivory can be managed with fencing. The mycorrhizal requirement is a
fundamental biotic constraint that is difficult to overcome.
4 A meta-analysis of 150 studies on species range shifts in response to climate
change found that, on average, species have shifted poleward at a rate of 16.9 km
per decade. However, the rates were significantly lower for species from tropical
regions (6.2 km/decade) compared to temperate regions (22.5 km/decade). Which
hypothesis best explains this discrepancy?
A) Tropical species have narrower thermal tolerances and are therefore more likely
to disperse to track climate.
B) Temperate regions have experienced greater warming rates than tropical regions
over the study period.
C) Tropical species face greater dispersal barriers due to habitat fragmentation in
human-dominated landscapes.
D) Temperate species are more likely to be generalists and can adapt to a wider
range of conditions, facilitating range shifts.
Answer: B
Rationale: The rate of climate change (warming) has been faster at higher latitudes,
so species in temperate regions need to shift faster to stay within their climatic
niche. Tropical regions have experienced less warming, so the required shift rate is
lower. Option A is opposite: narrow tolerances would make tracking more urgent,
not slower. While fragmentation can be a factor, it is not consistently higher in
tropics. Generalism does not necessarily translate to faster shifts.
5 In a forest ecosystem, elevated CO (eCO) increases tree growth and leaf area.
However, a long-term free-air CO enrichment (FACE) experiment shows that after
10 years, the net primary productivity (NPP) of the forest stops increasing despite
continued eCO. Which of the following is the most likely explanation for this
NPP plateau?
A) Photosynthetic acclimation reduces the sensitivity of Rubisco to CO over time.
B) Nitrogen limitation constrains further biomass accumulation as the forest
reaches nutrient carrying capacity.
, C) Increased leaf area leads to higher canopy temperatures and increased
respiration costs.
D) Herbivory increases due to higher leaf nitrogen content, reducing net carbon
gain.
Answer: B
Rationale: In many FACE experiments, the initial growth enhancement from eCO ‚ is
limited by nitrogen availability, as plants require more N to build new tissues. Once
the available N is sequestered in biomass, further growth is constrained. While
acclimation can occur, it is not the primary cause of plateau in long-term studies.
Increased respiration and herbivory are secondary effects that may contribute but are
not the main limiting factor.
6 A climate model predicts that under RCP 8.5, the mean global temperature will
increase by 4.5°C by 2100. Assuming a Q of 2 for metabolic rates of ectothermic
animals, by what factor would the metabolic rate of a typical insect increase if its
body temperature tracks ambient temperature?
A) 1.5
B) 2.0
C) 2.8
D) 4.0
Answer: A
Rationale: With a Q • € of 2, a 10°C increase doubles metabolic rate. For a 4.5°C
increase, the factor is 2^(4.5/10) 1.37, which rounds to 1.5 among the given options.
The other options overestimate the increase: 2.0 would require a 10°C rise, 2.8
would require ~15°C, and 4.0 would require a 20°C rise.
7 A researcher models the persistence of a metapopulation of a butterfly species
under climate change. The patches are arranged along a latitudinal gradient. The
extinction probability of each patch increases with temperature, and colonization
probability decreases with distance from source patches. Which of the following
scenarios would most likely lead to metapopulation collapse?
A) Temperature increases uniformly across all patches, but dispersal distances
remain unchanged.
B) Temperature increases more at the northern edge, reducing extinction there,
while southern patches become uninhabitable.
C) Temperature increases more at the southern edge, causing local extinctions, and
dispersal from northern patches is insufficient to recolonize southern patches due
to increased distance.
150 Questions
This exam assesses advanced understanding of the interactions between climate change and biodiversity,
including species responses, ecosystem dynamics, conservation strategies, and policy implications. It emphasizes
quantitative reasoning, synthesis of recent literature, and application to real-world scenarios. It contains 150
multiple-choice questions, each with four distractors and a fully worked rationale that explains why the keyed
answer is correct. Content is organized into 10 focused sections: Climate Change and Biodiversity, Genetically
Modified Organisms (GMOs), Emerging Infectious Diseases, CRISPR and Gene Editing Ethics, Human
Population Growth and Sustainability, Conservation Biology and Endangered Species, Stem Cell Research and
Regenerative Medicine, Antibiotic Resistance, Personalized Medicine and Genomics, Environmental Pollution and
Human Health. Targeted learning outcomes include: Evaluate the mechanisms by which climate change drives
biodiversity loss; Analyze species' adaptive responses and extinction risks under different climate scenarios;
Critically assess conservation interventions and their effectiveness in mitigating climate impacts; Interpret climate
and biodiversity data from multiple sources. Every item has been reviewed for clinical accuracy, current
guidelines, and clarity so that students can study with confidence and self-correct as they work through the bank.
Use it as a high-yield review immediately before the exam, or as a structured practice tool during the unit - the
rationales double as concise teaching notes. The recommended writing time is 3 hours, with a passing score of
Section 1: Climate Change and Biodiversity (Questions 1-15)
1 A study of tropical montane bird communities along an elevational gradient from
1000 to 3000 m finds that over the past 20 years, the mean elevation of bird
abundances has shifted upward by an average of 35 m per decade. However, the
rate of upward shift varies among species: insectivores shift faster than frugivores,
and species with smaller body sizes shift faster than larger ones. Which of the
following best explains the observed variation in shift rates?
A) Insectivores are more sensitive to temperature increases than frugivores due to
higher metabolic rates.
B) Larger-bodied species have greater dispersal capabilities and can track climate
more effectively.
C) Frugivores depend on fruit availability, which may be more constrained by
photoperiod than temperature, slowing their range shifts.
D) Smaller species have shorter generation times, allowing faster evolutionary
adaptation to new thermal regimes.
Answer: C
Rationale: Frugivores rely on fruit resources that are often triggered by photoperiod,
not temperature alone, so their resource availability may not shift as quickly as
temperature isotherms. Insectivores, feeding on temperature-sensitive insects, track
climate more directly. Body size and generation time are less directly linked to shift
rate; dispersal ability (often higher in larger species) would predict faster shifts,
opposite to the observation.
,2 In a study of coral reef ecosystems, researchers measured net primary production
(NPP) and calcification rates across a gradient of ocean acidification (OA) and
warming. They found that at pCO levels of 800 atm and temperature 2°C above
current, NPP increased by 15% but calcification decreased by 40%. Based on
these findings, what is the most likely net effect on the reef's ability to maintain
positive net ecosystem calcification (NEC) under projected end-of-century
conditions?
A) NEC will increase because higher NPP provides more organic matrix for
calcification.
B) NEC will decrease because the decline in calcification outweighs the increase
in NPP.
C) NEC will remain stable because increased photosynthesis buffers pH and
promotes calcification.
D) NEC will become negative, causing net erosion, because the decline in
calcification is greater than the increase in NPP can compensate.
Answer: D
Rationale: Net ecosystem calcification is the balance between gross calcification and
dissolution. A 40% decrease in calcification is substantial, and while NPP increases,
the organic matter produced does not directly contribute to calcification and may
even enhance dissolution via respiration. Thus, NEC likely becomes negative,
leading to net erosion. The pH buffering from increased photosynthesis is
insufficient to offset the direct effects of OA on calcification.
3 A conservation biologist is evaluating the effectiveness of assisted colonization
for a tree species (Pinus albicaulis) whose current habitat is projected to become
climatically unsuitable by 2080. The species has a generation time of 30 years and
low seed dispersal distance. The target site is 200 km north of the current range,
but the soil mycorrhizal community differs. Which of the following additional
considerations would most strongly argue against proceeding with assisted
colonization?
A) The target site has 20% lower annual precipitation than the current site.
B) The target site currently hosts a different species of pine that is competitively
superior.
C) The target site lacks the specific ectomycorrhizal fungi required by P. albicaulis,
and inoculation trials show low survival.
D) The target site is within the current range of a native herbivore that feeds on
pine seedlings.
,Answer: C
Rationale: Assisted colonization success critically depends on mutualistic
interactions. Without the appropriate mycorrhizal symbionts, the tree cannot obtain
sufficient nutrients, leading to high mortality. While precipitation and competition
are important, they can sometimes be mitigated or are less immediately lethal.
Herbivory can be managed with fencing. The mycorrhizal requirement is a
fundamental biotic constraint that is difficult to overcome.
4 A meta-analysis of 150 studies on species range shifts in response to climate
change found that, on average, species have shifted poleward at a rate of 16.9 km
per decade. However, the rates were significantly lower for species from tropical
regions (6.2 km/decade) compared to temperate regions (22.5 km/decade). Which
hypothesis best explains this discrepancy?
A) Tropical species have narrower thermal tolerances and are therefore more likely
to disperse to track climate.
B) Temperate regions have experienced greater warming rates than tropical regions
over the study period.
C) Tropical species face greater dispersal barriers due to habitat fragmentation in
human-dominated landscapes.
D) Temperate species are more likely to be generalists and can adapt to a wider
range of conditions, facilitating range shifts.
Answer: B
Rationale: The rate of climate change (warming) has been faster at higher latitudes,
so species in temperate regions need to shift faster to stay within their climatic
niche. Tropical regions have experienced less warming, so the required shift rate is
lower. Option A is opposite: narrow tolerances would make tracking more urgent,
not slower. While fragmentation can be a factor, it is not consistently higher in
tropics. Generalism does not necessarily translate to faster shifts.
5 In a forest ecosystem, elevated CO (eCO) increases tree growth and leaf area.
However, a long-term free-air CO enrichment (FACE) experiment shows that after
10 years, the net primary productivity (NPP) of the forest stops increasing despite
continued eCO. Which of the following is the most likely explanation for this
NPP plateau?
A) Photosynthetic acclimation reduces the sensitivity of Rubisco to CO over time.
B) Nitrogen limitation constrains further biomass accumulation as the forest
reaches nutrient carrying capacity.
, C) Increased leaf area leads to higher canopy temperatures and increased
respiration costs.
D) Herbivory increases due to higher leaf nitrogen content, reducing net carbon
gain.
Answer: B
Rationale: In many FACE experiments, the initial growth enhancement from eCO ‚ is
limited by nitrogen availability, as plants require more N to build new tissues. Once
the available N is sequestered in biomass, further growth is constrained. While
acclimation can occur, it is not the primary cause of plateau in long-term studies.
Increased respiration and herbivory are secondary effects that may contribute but are
not the main limiting factor.
6 A climate model predicts that under RCP 8.5, the mean global temperature will
increase by 4.5°C by 2100. Assuming a Q of 2 for metabolic rates of ectothermic
animals, by what factor would the metabolic rate of a typical insect increase if its
body temperature tracks ambient temperature?
A) 1.5
B) 2.0
C) 2.8
D) 4.0
Answer: A
Rationale: With a Q • € of 2, a 10°C increase doubles metabolic rate. For a 4.5°C
increase, the factor is 2^(4.5/10) 1.37, which rounds to 1.5 among the given options.
The other options overestimate the increase: 2.0 would require a 10°C rise, 2.8
would require ~15°C, and 4.0 would require a 20°C rise.
7 A researcher models the persistence of a metapopulation of a butterfly species
under climate change. The patches are arranged along a latitudinal gradient. The
extinction probability of each patch increases with temperature, and colonization
probability decreases with distance from source patches. Which of the following
scenarios would most likely lead to metapopulation collapse?
A) Temperature increases uniformly across all patches, but dispersal distances
remain unchanged.
B) Temperature increases more at the northern edge, reducing extinction there,
while southern patches become uninhabitable.
C) Temperature increases more at the southern edge, causing local extinctions, and
dispersal from northern patches is insufficient to recolonize southern patches due
to increased distance.
