AP Environmental Science Quiz: K Selected And R Selected Species

What this quiz covers

This quiz focuses on K Selected And R Selected Species, 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. Its r-selected strategy depends on frequent disturbance to reduce competition
2. Its K-selected strategy means slow population growth, so losses are replaced slowly (correct answer)
3. Its high fecundity causes rapid overshoot and collapse after disturbance
4. Its short lifespan makes it unable to recolonize after disturbance

Explanation: K-selected species, with slow growth, low fecundity, and high care, are vulnerable to disruption as they replace losses slowly in stable habitats. r-selected species recover quickly from disturbances. The bird's one egg and long care indicate K-selection, making habitat disruption harmful due to slow population rebound. This explains prioritization for protection, as K-traits limit rapid recovery. Conservation must focus on maintaining stable nesting sites.

Question 2

1. Population remains stable near $K$ because K-selected traits buffer against disturbance
2. Population crashes when pools dry, but recolonizes rapidly when pools return due to r-selected traits (correct answer)
3. Population increases during drying because competition decreases
4. Population is unaffected because lifespan is long and reproduction is delayed

Explanation: r-selected species in temporary habitats show rapid recolonization after crashes due to high fecundity and quick hatching. K-selected are stable. The crustacean's many quick-hatching eggs predict population crashes on drying but fast recovery on refilling, via r-traits. This response suits unpredictable pool durations. It highlights r-adaptation to frequent disturbances.

Question 3

1. FF becomes more common because K-selected traits are favored by disturbance
2. EE becomes more common because r-selected traits are favored by unpredictable conditions (correct answer)
3. Both become less common because r/K selection only applies to plants
4. EE becomes more common because fewer offspring increase survival during extreme events

Explanation: r-selected species with short lifespans, many offspring, and no care are resilient to disturbances and unpredictable conditions. K-selected species with long lifespans, few offspring, and care are vulnerable to frequent extremes, as recovery is slow. The shift to extreme events would favor EE's r-selected traits, making it more common. FF's K-traits would disadvantage it in instability. r/K selection applies broadly, not just to plants. Option B predicts the likely outcome.

Question 4

1. A stable climax community where populations remain near carrying capacity
2. A frequently disturbed habitat where mortality is high and conditions change unpredictably (correct answer)
3. A habitat with constant resources and low mortality where long lifespan is favored
4. A habitat where parental care is required for any offspring to survive

Explanation: r-selected species have high intrinsic growth rates (r), early maturity, and many offspring, evolved for disturbed habitats with high, unpredictable mortality. K-selected species have lower r, later maturity, and fewer offspring, for stable environments near K. Species CC's traits indicate r-selection, best suited to frequently disturbed habitats where rapid reproduction exploits opportunities. Stable habitats would favor K-traits like long lifespans. Parental care isn't required here, as quantity compensates for mortality. Option B identifies the selecting environment.

Question 5

1. Unpredictable disturbance selecting for rapid reproduction
2. Competition for resources near carrying capacity selecting for efficient resource use and high offspring survival (correct answer)
3. High juvenile mortality selecting for millions of offspring
4. Short lifespan selecting for early reproduction and no parental care

Explanation: K-selected traits evolve under competition near carrying capacity in stable environments, favoring efficient resource use and high offspring survival. r-selection responds to disturbance with rapid reproduction. The herbivore's long gestation, single offspring, and care suggest K-selection shaped by resource competition in the stable savanna. This limiting factor selects for investments that enhance survival amid density-dependent pressures. It explains why such traits persist where predictability allows competition to dominate.

Question 6

1. The mowed patch will favor more r-selected traits such as earlier reproduction and higher litter sizes (correct answer)
2. The mowed patch will favor more K-selected traits such as delayed maturity and fewer offspring
3. Both patches will favor identical traits because genetics prevents life-history shifts
4. The stable patch will favor r-selected traits because competition is strongest there

Explanation: r-selected traits like early reproduction and large litters are favored in disturbed, high-mortality environments to maximize survivors. K-selected traits, such as delayed maturity and fewer offspring, suit stable, competitive habitats. The mowed patch's frequent disturbances would select for more r-selected traits in rabbits, like higher litter sizes, to counter mortality. In the stable meadow, moderate traits persist due to lower disturbance. Genetics can allow shifts over time via natural selection. Option A correctly predicts the divergence.

Question 7

1. High juvenile mortality and no parental care
2. Early reproduction and many small offspring
3. Long lifespan and high investment per offspring (correct answer)
4. Rapid population growth when density is high due to low competition

Explanation: In K-selection, species invest in traits like long lifespans, delayed maturity, few offspring, and high parental care to succeed in stable, resource-limited environments near carrying capacity. r-selected species prioritize rapid reproduction, many small offspring, and little care for unpredictable habitats. Species M's slow maturity, few offspring, and territorial defense suggest K-selection, fitting the stable island with limited food where competition is key. Compared to r-selected species, a long lifespan and high investment per offspring would be expected, as these enhance competitive ability and survival rates in density-dependent conditions. This trade-off allows K-selected species to maximize fitness when resources are consistently scarce but predictable.

Question 8

1. Species A increases because stable conditions favor rapid reproduction and early maturity
2. Species B increases because stable conditions favor K-selected traits and competitive ability near $K$ (correct answer)
3. Both species increase equally because environmental stability benefits all life histories
4. Species B declines because parental care is maladaptive when resources are predictable

Explanation: K-selection favors traits like few offspring, extensive parental care, and long lifespans in stable, competitive environments near carrying capacity, while r-selection promotes many offspring, quick maturity, and short lifespans in disturbed, unpredictable settings. Species A exhibits r-selected traits, thriving after disturbances like floods, whereas Species B shows K-selected characteristics, dominating in undisturbed habitats. Stabilizing the river with a dam reduces disturbances, creating a more predictable environment that favors K-selected species like B, which can outcompete others through superior resource use and offspring investment. Over time, this shift would lead to an increase in Species B as competitive pressures near K limit r-selected species. The change highlights how environmental stability selects for K-traits that enhance survival in density-dependent conditions.

Question 9

1. Strictly r-selected because any disturbance selects for maximum offspring production
2. Strictly K-selected because any parental care indicates K-selection
3. Intermediate on the r–K continuum, with traits reflecting both disturbance and competition (correct answer)
4. Neither r nor K because carrying capacity applies only to plants

Explanation: Life histories exist on an r-K continuum, with intermediates blending traits for moderately variable environments. Strict r or K applies to extremes. Species U's 10 offspring, moderate care, 5-year lifespan, and variable environment suggest an intermediate position, reflecting both disturbance adaptation and some competition. This best describes it as environments aren't purely unstable or stable. The continuum allows nuanced classification beyond binaries.

Question 10

1. r-selected; advantage is rapid colonization after frequent disturbances
2. K-selected; advantage is higher survival of few offspring in a stable environment with competition for resources (correct answer)
3. r-selected; advantage is maximizing offspring number when near carrying capacity
4. K-selected; advantage is producing many offspring to offset unpredictable, high juvenile mortality

Explanation: K-selected species exhibit traits optimized for stable environments with high competition near carrying capacity: long lifespan, delayed reproduction, few offspring, and extensive parental care. R-selected species show opposite traits suited for unstable environments: short lifespan, early reproduction, many offspring, and minimal parental care. This cliff-nesting bird displays classic K-selected traits: laying only 1-2 eggs annually, both parents providing extended care for months, and individuals living over 20 years in an environment with consistent food supply and climate. The key advantage of K-selection in stable environments is that heavy investment in few offspring ensures high juvenile survival rates when competition for resources is intense. By feeding chicks for months, both parents ensure their offspring develop the size, strength, and skills needed to compete successfully in a crowded, stable environment. Option B correctly identifies this as K-selected and explains the advantage as higher survival of few offspring in a stable environment with competition for resources.

Question 11

1. Stable environment and intense competition near carrying capacity
2. Unstable, unpredictable habitat where many offspring increase the chance some survive (correct answer)
3. Low reproductive output requiring high investment per offspring
4. Long lifespan and delayed maturity to avoid disturbance

Explanation: r-selected species prioritize rapid population growth through high fecundity, minimal parental care, and quick maturation, suited to unpredictable environments where many offspring increase survival odds. K-selected species, however, invest heavily in fewer offspring for stable, competitive settings near carrying capacity. The mosquito's strategy of laying hundreds of eggs without care and developing quickly is a hallmark of r-selection, enabling it to exploit temporary water sources before they dry out or are emptied. This approach is most favored by unstable, unpredictable habitats, as the sheer number of offspring ensures some survive despite high mortality from environmental disturbances. In contrast, stable environments would favor K-selected traits like high investment per offspring. Thus, option B accurately highlights the key environmental factor driving this life-history strategy.

Question 12

1. Frequent large oscillations far above and below carrying capacity
2. Growth slows as population approaches carrying capacity, remaining relatively stable near $K$ (correct answer)
3. Exponential growth indefinitely because competition is minimal in stable habitats
4. Population size is primarily limited by producing too many offspring

Explanation: K-selected species exhibit low reproduction, high investment, and strong competition, leading to populations stabilizing near carrying capacity (K) in stable environments. r-selected species show rapid growth and oscillations in disturbed habitats. Species Q's traits suggest K-selection, predicting growth slowing near K with relative stability due to density-dependent factors like nesting competition. This pattern arises because investments in survival and competition prevent overshoots. In temperate forests, such stability contrasts with r-selected boom-busts.

Question 13

1. K-selected because it relies on high competition in stable habitats
2. r-selected because it exploits disturbed environments with rapid reproduction (correct answer)
3. K-selected because it produces many offspring
4. r-selected because it produces few offspring with high parental care

Explanation: r-selected species like weeds exploit disturbed agricultural fields with many seeds, short generations, and rapid growth when resources abound. K-selected differ in stable settings. Species V's traits classify it as r-selected for colonizing post-plowing areas. This fits because disturbances create opportunities for quick exploitation. It contrasts with K-competitive stability.

Question 14

1. Even fewer offspring and less parental care to reduce energy use
2. Greater parental investment per offspring (e.g., more guarding) to increase survival in a competitive, stable setting (correct answer)
3. Shift to producing millions of eggs with no care because stable habitats always favor r-selection
4. Shorter lifespan and earlier maturity because K-selected species cannot adapt

Explanation: In stable environments with increased mortality, K-selected species may evolve greater per-offspring investment to boost survival. The salamander's small, guarded eggs suggest K-selection, so higher guarding would be selected against invasive predators. This change maintains fitness in competitive, stable lakes by enhancing juvenile survival. It reflects adaptation within K-strategy. Fewer offspring with more care is a common response.

Question 15

1. Slow increase because K-selected species require stable habitats to reproduce
2. Rapid exponential-like increase initially because r-selected traits allow fast growth at low density (correct answer)
3. Immediate stabilization near carrying capacity because competition is strongest at low density
4. Decline because producing many seeds reduces survival in disturbed habitats

Explanation: r-selected species excel in disturbed or low-density environments due to traits like high seed production, early maturity, and rapid growth, leading to exponential population increases when resources are abundant. K-selected species grow more slowly, focusing on competitive traits in stable habitats near K. Species Z's ability to produce many seeds and mature in one season positions it as r-selected, ideal for quick colonization of newly cleared areas. In such disturbed soils with low initial density, the population would exhibit rapid, exponential-like growth before density-dependent factors slow it down. This pattern contrasts with the slower establishment of K-selected plants. Therefore, option B best predicts the short-term growth.

Question 16

1. K-selected; benefit is stable populations near $K$ through high parental care
2. r-selected; benefit is rapid reproduction and dispersal to exploit newly available habitat after disturbance (correct answer)
3. K-selected; benefit is delayed maturity to avoid flood seasons
4. r-selected; benefit is producing few offspring to reduce competition

Explanation: r-selected species have short life cycles, many offspring, and low investment, benefiting from rapid exploitation of disturbed habitats. K-selected species delay reproduction for stability. Species GG's traits fit r-selection, with the primary benefit being quick dispersal and reproduction post-flooding. This allows colonization of new areas. High care or few offspring wouldn't suit disturbances. Option B identifies the strategy and benefit.

Question 17

1. A modest increase rather than an extreme boom, because reproduction rate is constrained by low fecundity and longer generation time (correct answer)
2. A rapid population explosion because K-selected species have the highest $r$
3. No change because K-selected species cannot respond to resource changes
4. A crash first, followed by growth, because parental care increases mortality

Explanation: K-selected species respond modestly to resource increases due to low fecundity, high investment per offspring, and longer generation times, unlike r-selected species' rapid booms. r-selected traits allow explosive growth with many offspring in favorable conditions. For Species DD, a nutrient pulse would lead to a modest increase, constrained by its K-selected biology. This contrasts with r-selected species' potential for extreme booms. No change or crashes wouldn't occur, as resources are temporarily abundant. Option A is consistent with K-selection.

Question 18

1. K-selected; few offspring and high parental care maximize survival near carrying capacity in stable habitats
2. r-selected; many offspring and rapid maturation increase the chance some survive in unpredictable, disturbed habitats (correct answer)
3. K-selected; long lifespan and delayed reproduction are favored when resources are temporarily abundant after disturbance
4. r-selected; few offspring with intensive care are favored when competition is strong and the environment is stable

Explanation: K-selected species are those that produce few offspring, invest heavily in parental care, and have longer lifespans, thriving in stable environments where populations are near the carrying capacity (K) due to intense competition. In contrast, r-selected species produce many offspring with little to no parental care, mature quickly, and have short lifespans, which allows them to exploit unpredictable or disturbed habitats through rapid population growth. For Species X, the traits of rapid maturation, high offspring number, no parental care, short lifespan, and boom-bust cycles align with r-selection. These characteristics are advantageous in the post-volcanic island setting because the environment is unstable with frequent disturbances like droughts, where producing many offspring increases the likelihood that some will survive to reproduce during brief favorable periods. This strategy maximizes reproductive success in habitats where mortality is high and unpredictable, rather than investing in fewer, better-cared-for offspring as K-selected species do in stable conditions.

Question 19

1. K-selected; slow growth and high parental care stabilize the population near $K$
2. r-selected; rapid reproduction allows quick exploitation of temporary favorable conditions (correct answer)
3. K-selected; delayed reproduction increases survival when disturbance is frequent
4. r-selected; few offspring reduce competition in stable environments

Explanation: r-selected species, like bacteria, use rapid reproduction to exploit temporary conditions in fluctuating environments. K-selected species stabilize near K in predictable settings. The bacterial population's quick doubling fits r-selection, allowing exploitation of nutrient-rich but changing conditions like temperature or antibiotics. This strategy enables fast growth during favorable times, offsetting high mortality. It contrasts with K-selected slow, competitive growth.

Question 20

1. Species 1 is K-selected; Species 2 is r-selected
2. Species 1 is r-selected; Species 2 is K-selected (correct answer)
3. Both are K-selected because they live in a stable lake
4. Both are r-selected because fish generally produce many offspring

Explanation: r-selected species produce vast numbers of offspring with no parental care, relying on quantity to offset high mortality in unstable environments. K-selected species produce fewer offspring but provide extensive care, favoring stable habitats where investment improves survival amid competition. In the stable lake, Species 1's millions of unguarded eggs indicate r-selection, while Species 2's small, guarded clutch points to K-selection. This pairing is accurate because even in stable environments, r-selected species can persist if mortality remains high for unprotected offspring, but K-traits like guarding enhance competitiveness. The classification reflects how life histories adapt to specific reproductive risks and environmental predictability.