AP Environmental Science Quiz: Ecological Tolerance

What this quiz covers

This quiz focuses on Ecological Tolerance, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Environmental Science.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. 16°C
2. 20°C (correct answer)
3. 12°C
4. 6°C

Explanation: Ecological tolerance defines survival limits, like temperature for trout. The curve shows maximal 12–16°C, stress 6–12°C and 16–20°C, zero outside 6–20°C. 20°C is the upper limit. Others are within or below. Choice B represents it. Critical for fisheries under warming.

Question 2

1. 18°C
2. 3°C
3. 27°C (correct answer)
4. 32°C

Explanation: Ecological tolerance encompasses conditions for growth, such as nighttime temperature. The curve peaks at 15–20°C, stresses at 5–15°C and 20–30°C, zeros outside 5–30°C. 27°C is in upper stress, allowing growth but stressed. 32°C is beyond. Choice C fits. Relevant for desert plant ecology.

Question 3

1. 6 ppt
2. 15 ppt
3. 29 ppt (correct answer)
4. 31 ppt

Explanation: Ecological tolerance influences coastal species' salinity endurance. The tolerance curve peaks highly, reduces towards limits, zeros outside. Highest 10–20 ppt, reduced 5–10 and 20–30 ppt, zero below 5 or above 30. 29 ppt is in upper reduced zone, near limit, likely lowest survival within tolerance. This is due to approaching zero at 30 ppt. Choice C produces lowest within-limits survival.

Question 4

1. pH 6.4
2. pH 7.2 (correct answer)
3. pH 8.2
4. pH 8.6

Explanation: Ecological tolerance outlines the environmental parameters a species can endure, crucial for abundance and distribution. The tolerance curve peaks in the optimal range where abundance is greatest, flanked by stress zones with lower abundance, and ends at tolerance limits with zero abundance. For this macroinvertebrate, abundance is highest at pH 6.8–7.6, reduced at 6.0–6.8 and 7.6–8.4, and zero outside 6.0–8.4. The pH 7.2 falls squarely in the optimal range, likely yielding the greatest abundance. Other options are either in stress zones or closer to limits. This makes choice B the best for maximal abundance.

Question 5

1. 150
2. 300
3. 500 (correct answer)
4. 650

Explanation: Ecological tolerance is the light intensity range for photosynthesis in kelp. The curve peaks at 200–400, stresses at 100–200 and 400–600, near zero outside. 500 is in upper stress. 650 beyond. Choice C correct. Aids in understanding marine productivity.

Question 6

1. The coral moves from optimal range into a zone of stress, so calcification decreases (correct answer)
2. The coral moves from a zone of stress into the optimal range, so calcification increases
3. The coral crosses the upper limit of tolerance, so calcification becomes impossible at 28°C
4. No change is expected because tolerance curves are flat near the optimum

Explanation: Ecological tolerance outlines conditions for species processes like calcification in corals. The tolerance curve shows optimal temperatures, stress zones with reduced rates, and limits nearing zero. Maximal at 25–27°C, reduced at 23–25°C and 27–29°C, near zero at 22°C and 30°C. Rising from 26°C (optimal) to 28°C shifts to upper stress, decreasing calcification. This is due to thermal stress affecting symbiosis. Choice A interprets this transition correctly.

Question 7

1. 5 units
2. 15 units (correct answer)
3. 30 units
4. 0 units

Explanation: Ecological tolerance is the spectrum of conditions a species can endure, vital for ecosystem roles. Tolerance curves depict growth versus factors like pollution, with optimal low-pollution, stress at moderate, and limits at high. Here, highest growth at 0–10 units, reduced (stress) at 10–25, zero above 25. The zone of stress is 10–25 units, where growth persists but diminishes. 15 units falls in this range. Choice B represents the stress zone condition.

Question 8

1. Activity is near maximum because 4°C is close to the optimum
2. Activity is reduced because 4°C is in the lower zone of stress but within tolerance limits (correct answer)
3. The worms cannot survive because 4°C is below the lower limit of tolerance
4. The worms cannot survive because 4°C is above the upper limit of tolerance

Explanation: Ecological tolerance is the temperature span for activity in worms. Nonzero from 2–28°C, optimal 12–18°C. 4°C is lower stress, reducing activity but survivable. Not optimal or beyond limits. Choice B likely. Shows winter resilience.

Question 9

1. 20°C
2. 2°C (correct answer)
3. 45°C
4. 19°C

Explanation: Ecological tolerance encompasses the range of conditions, such as temperature, where an organism can survive, though performance varies. A tolerance curve illustrates this with limits at 0°C and 40°C where performance is zero, stress zones with reduced performance, and an optimal range at 18–22°C for peak performance. The temperature of 2°C is within the tolerance limits but in the lower stress zone, yielding the lowest performance while still allowing survival. Temperatures like 45°C exceed the upper limit, making survival impossible. Choice B correctly identifies this. Such curves aid in predicting species' responses to climate variability.

Question 10

1. Survival remains high because 18 ppt is within the optimal range
2. Survival decreases but remains possible because 18 ppt is in a zone of stress
3. Survival drops to near zero because 18 ppt is below the lower limit of tolerance (correct answer)
4. Survival increases because lower salinity reduces osmotic stress for marine crabs

Explanation: Ecological tolerance is the range of an abiotic factor where a species can live, influencing its habitat distribution. The tolerance curve shows high survival in the optimal range, reduced in stress zones, and zero at the limits. For the crab, optimal survival is at 30–34 ppt, reduced at 20–30 and 34–40 ppt, and zero below 20 or above 40 ppt. Dropping to 18 ppt crosses below the lower limit of 20 ppt, where survival is zero. This predicts near-zero survival due to osmotic imbalance. Choice C correctly identifies this as exceeding the tolerance limit.

Question 11

1. Fish remain in a zone of stress, so growth slows but survival is likely
2. Fish remain in the optimal range, so growth stays maximal
3. Fish exceed the upper limit of tolerance, so mortality is expected (correct answer)
4. Fish exceed the lower limit of tolerance, so mortality is expected

Explanation: Ecological tolerance is critical for aquatic species facing temperature fluctuations. Tolerance curves show growth optima, stress reductions, and survival limits. Max growth 24–28°C, reduced 18–24°C and 28–32°C, no survival below 18°C or above 32°C. At 33°C, exceeds upper limit, expecting mortality. This is due to physiological failure beyond tolerance. Choice C predicts this outcome.

Question 12

1. Both species will thrive equally because 3 mg/L is within both optimal ranges
2. Species Y is more likely to survive than Species X because it has a wider tolerance range
3. Species X is more likely to survive than Species Y because 3 mg/L is above X's lower limit but below Y's lower limit (correct answer)
4. Neither species can survive because 3 mg/L is below both lower limits of tolerance

Explanation: Ecological tolerance is the ability of a species to persist under varying environmental conditions, defined by lower and upper limits. A tolerance curve graphs survival or performance against the factor, with an optimal peak, stress zones, and limits where survival is impossible. Here, Species X tolerates 2–14 mg/L DO with max at 8, while Y tolerates 5–12 mg/L with max at 9, so at 3 mg/L, X is above its lower limit (stressed but survivable) but Y is below its lower limit (unsurvivable). Thus, X is more likely to survive than Y in low DO conditions. This prediction is supported by comparing tolerance ranges. Choice C correctly captures this competitive advantage for X.

Question 13

1. 10%
2. 2%
3. 14% (correct answer)
4. 9%

Explanation: Ecological tolerance describes the spectrum of abiotic factors, like sugar concentration, that an organism can endure, from lethal limits to optimal conditions. The tolerance curve maps performance, such as fermentation rate, showing zero at extremes, reduced in stress zones, and maximal in the optimal range. Here, the yeast's optimal range is 8–12% sugar, with stress zones at 4–8% and 12–16%, and zero outside those. A concentration of 14% falls in the 12–16% stress zone, where fermentation is reduced but possible. Thus, choice C is correct as it identifies a stress zone. This demonstrates how organisms can persist in suboptimal conditions but with impaired function, which is key in environmental science for understanding adaptation.

Question 14

1. Increase salinity to 38 ppt
2. Decrease salinity to about 20 ppt (correct answer)
3. Decrease salinity to 3 ppt
4. Increase salinity to 33 ppt

Explanation: Ecological tolerance for mangrove survival is maximal at 15–25 ppt, stress at 5–15 and 25–35, zero outside. At 30 ppt (upper stress), decreasing to 20 ppt shifts to optimal. Increasing worsens. Choice B best. Guides restoration efforts.

Question 15

1. Both species are in their optimal ranges, so both perform maximally
2. Species 1 can survive (likely stressed or near optimal), while Species 2 is below its lower limit of tolerance (correct answer)
3. Species 2 can survive (likely stressed), while Species 1 is below its lower limit of tolerance
4. Neither species can survive because pH 5.0 is outside both tolerance ranges

Explanation: Ecological tolerance varies between species, affecting coexistence in habitats. Tolerance curves compare ranges, showing survival possibilities. Species 1 survives pH 4.5–7.5 (optimal 5.5–6.5), so at 5.0 it is within limits, likely stressed. Species 2 survives 6.0–8.5, so 5.0 is below its lower limit, preventing survival. This gives Species 1 an edge in acidic soils. Choice B correctly predicts Species 1's survival over 2.

Question 16

1. Both species are below their lower limits, so neither will survive
2. Species A can survive (likely stressed), while Species B is below its lower limit of tolerance (correct answer)
3. Species B can survive (likely stressed), while Species A is below its lower limit of tolerance
4. Both species are in their optimal ranges, so survival and performance are maximal

Explanation: Ecological tolerance defines survivable environmental ranges, influencing species resilience to changes. Tolerance curves show broad or narrow ranges, with optimal sub-ranges for peak performance. Species A tolerates 5–35°C (optimal 20–25°C), so at 8°C it is stressed but within limits. Species B tolerates 12–30°C, so 8°C is below its lower limit, preventing survival. This highlights A's wider tolerance for cold. Choice B correctly predicts A's survival advantage.

Question 17

1. Growth increases because 1.5 mg/L is closer to the optimum
2. Growth decreases because conditions shift from optimal range to a zone of stress (correct answer)
3. Growth becomes impossible because 1.5 mg/L is above the upper limit of tolerance
4. No change occurs because the tolerance curve is symmetric and flat

Explanation: Ecological tolerance governs nutrient responses in phytoplankton. Tolerance curves peak at optimal concentrations, decline in stress, near zero at limits. Maximal at 0.8–1.2 mg/L, reduced 0.4–0.8 and 1.2–1.6, near zero outside 0.4–1.6. From 1.0 (optimal) to 1.5 shifts to upper stress, decreasing growth. This reflects nutrient toxicity stress. Choice B interprets this change correctly.

Question 18

1. Optimal range: 6–26°C; zones of stress: 12–20°C; limits of tolerance: 16°C only
2. Optimal range: 12–20°C; zones of stress: 6–12°C and 20–26°C; limits of tolerance: 6°C and 26°C (correct answer)
3. Optimal range: 6–12°C and 20–26°C; zones of stress: 12–20°C; limits of tolerance: 12°C and 20°C
4. Optimal range: 16–26°C; zones of stress: 6–16°C; limits of tolerance: 12°C and 20°C

Explanation: Ecological tolerance refers to the range of environmental conditions, such as temperature, within which a species can survive and function. A tolerance curve typically illustrates this as a bell-shaped graph, with the optimal range at the peak where performance or survival is highest, zones of stress on either side where performance declines but survival is possible, and limits of tolerance at the extremes where survival drops to zero. In this case, the mayfly nymph's survival peaks at 16°C with 100% survival, declines to 60% at 12°C and 20°C, and reaches 0% at 6°C and 26°C, indicating the optimal range is between 12–20°C where survival is still relatively high. The zones of stress are 6–12°C and 20–26°C, where survival decreases gradually to zero. The limits of tolerance are at 6°C and 26°C, beyond which no survival occurs. This matches choice B, as it correctly identifies these ranges based on the curve's description.

Question 19

1. Species B should have higher fitness because 18°C is closer to its upper limit of tolerance.
2. Species A should have higher fitness because 18°C falls within its optimal range, while Species B is in a zone of stress. (correct answer)
3. Both species should have equal fitness because 18°C is within both species' limits of tolerance.
4. Neither species can survive because 18°C is below both lower limits of tolerance.

Explanation: Ecological tolerance curves help predict competitive outcomes by showing which species perform best under specific conditions. Species A survives from 8-26°C with optimal performance at 16-20°C, while Species B survives from 14-32°C with optimal performance at 24-28°C. At the pond's consistent 18°C temperature, Species A is within its optimal range (18°C falls within 16-20°C) and should exhibit maximum growth, reproduction, and overall fitness. In contrast, Species B is below its optimal range and likely in a zone of stress, as 18°C is well below its preferred 24-28°C range but still within its survival limits. When one species is in optimal conditions while another is stressed, the optimally-suited species typically has competitive advantages in resource acquisition and reproduction. Option B correctly predicts Species A's higher fitness due to optimal conditions versus Species B's stressed state.

Question 20

1. 38 ppt
2. 41 ppt (correct answer)
3. 33 ppt
4. 28 ppt

Explanation: Ecological tolerance sets the boundaries for species functions like feeding, graphed in tolerance curves. The curve peaks optimally, reduces in stress, and zeros at limits. For the snail, maximal feeding at 33 ppt, reduced to 28–38 ppt, zero at 25 and 41 ppt, so upper limit is 41 ppt. This is where feeding ceases. Other values are within reduced or optimal. Choice B is closest to the upper tolerance limit.