AP Biology Quiz: Artificial Selection

What this quiz covers

This quiz focuses on Artificial Selection, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Biology.

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. The distribution shifts toward finer fibers because allele W became more common among reproducing parents. (correct answer)
2. The distribution stays unchanged because phenotype distributions cannot shift without new alleles entering by migration.
3. The distribution shifts toward coarser fibers because selecting fine wool increases the frequency of allele w.
4. The distribution shifts toward finer fibers because each sheep produces finer wool after exposure to selective breeding.
5. The distribution becomes bimodal because selection forces both alleles to equal frequencies in every generation.

Explanation: This question tests understanding of how changes in allele frequency affect phenotype distributions. As selection for fine wool increases allele W's frequency from 0.55 to 0.90, more sheep inherit W alleles (as WW or Ww), shifting the population's phenotype distribution toward finer fibers because genotypes producing finer wool become more common. This demonstrates the connection between allele frequency changes and observable trait distributions in populations. Option B incorrectly claims distributions cannot shift without migration; option C contradicts the selection direction; option D suggests individual phenotypic change rather than population evolution; option E misunderstands selection's effect on allele frequencies. To predict phenotypic outcomes, connect allele frequency changes to the phenotypes those alleles produce in the population.

Question 2

1. The frequency of allele H increases because individuals with more H alleles leave more offspring. (correct answer)
2. Allele h becomes more common because selection creates new h mutations in low-yield calves.
3. Both alleles remain at the same frequencies because selection changes only phenotypes, not genes.
4. Allele frequencies fluctuate randomly because breeding choices eliminate any effect of selection.
5. Each cow increases its own H allele proportion during life in response to frequent milking.

Explanation: This question assesses the analysis of artificial selection, where humans selectively breed organisms for desired traits, leading to changes in population genetics. The correct answer is A because breeders allow only the highest milk-yield cows to reproduce, and since milk yield is influenced by allele H for higher yield, individuals carrying more H alleles contribute disproportionately to the next generation's gene pool. Over five generations, this differential reproductive success increases the frequency of H from 0.40, as low-yield calves with more h alleles are less likely to be born due to the selection pressure. This aligns with AP Biology concepts of evolution, where artificial selection mimics natural selection by favoring heritable traits that enhance reproductive output in the controlled environment. A tempting distractor is E, which is incorrect due to the misconception of Lamarckian inheritance, suggesting individuals acquire and pass on traits during their lifetime rather than through genetic selection. A transferable strategy for this question type is to identify how selective breeding amplifies alleles linked to the desired phenotype through generational reproduction, not individual adaptation.

Question 3

1. Alleles for shorter ears are maintained at the same frequency because they are recessive.
2. Ear-length alleles shift because rabbits stretch their ears more when long ears are preferred.
3. Genetic variation affecting ear length decreases as alleles for shorter ears are selected against. (correct answer)
4. New ear-length alleles appear because breeders repeatedly measure ear length.
5. The ear-length distribution narrows because selection cannot change allele frequencies.

Explanation: This question assesses the skill of analyzing artificial selection by analyzing changes in trait variation and means in mammalian breeding programs. The correct answer is choice C because selecting rabbits with the longest ears as parents reduces the transmission of alleles for shorter ears, decreasing genetic variation and narrowing the ear-length range while increasing the average, per the AP Biology principle that directional selection reduces diversity by eliminating unfavored alleles. The stimulus describes a narrower range after many generations, reflecting loss of shorter-ear variants due to consistent selection pressure. Ear length as a quantitative trait shows how repeated selection compresses phenotypic variation. A tempting distractor is choice B, which is incorrect due to the misconception of structure-function confusion, suggesting physical stretching alters heredity rather than genetic selection. To approach similar questions, assess variance changes alongside means to infer selection's impact on underlying genetic diversity.

Question 4

1. Survival increased because drought conditions caused all plants to develop the same protective allele.
2. Survival increased because alleles that contribute to drought survival became more frequent. (correct answer)
3. Survival increased because selection always increases genetic diversity at survival loci.
4. Survival increased because plants that died still passed their alleles to the next generation.
5. Survival increased because the corn population evolved drought resistance within each plant's lifetime.

Explanation: This question assesses the skill of analyzing artificial selection by determining how breeding for survival traits enhances population resilience in crops. The correct answer is choice B because crossing only high drought-survival corn plants increases the frequency of alleles conferring drought resistance, leading to higher survival rates after five generations, according to the AP Biology concept that selection enriches populations for beneficial alleles under consistent conditions. The stimulus specifies identical drought-stress protocols each generation, ensuring the observed increase in survival stems from genetic improvements. As a heritable trait, drought survival responds to selection by shifting the population toward more resistant genotypes. A tempting distractor is choice E, which is incorrect due to a level-of-organization error, confusing within-lifetime phenotypic plasticity with heritable evolutionary changes across generations. To approach similar questions, isolate genetic effects by noting controlled environments and track how selection favors alleles improving fitness-related traits.

Question 5

1. Line 1 mice ran faster because they trained harder after being selected as parents.
2. Line 2 mice ran slower because random mating removes alleles for fast running from populations.
3. Line 1 had increased frequency of alleles contributing to fast running due to nonrandom breeding. (correct answer)
4. Line 2 had more mutations because random breeding increases mutation rates at running genes.
5. The difference occurred because populations change traits to match breeder preferences over time.

Explanation: This question assesses the skill of analyzing artificial selection by comparing outcomes in selected versus control lines to isolate selection effects. The correct answer is choice C because Line 1's nonrandom breeding from the fastest 10% increases alleles for fast running, raising mean speed over 15 generations, consistent with the AP Biology concept that artificial selection drives evolutionary change by favoring specific genotypes. The stimulus contrasts Line 1 with randomly bred Line 2 under identical housing, attributing the speed difference to selection pressure. Running speed as a heritable trait demonstrates directional selection's impact. A tempting distractor is choice A, which is incorrect due to the misconception of teleology, suggesting mice train to meet selection criteria rather than inheriting advantageous alleles. To approach similar questions, use control groups to confirm selection's role and predict trait divergence based on breeding methods.

Question 6

1. Alleles associated with greater muscle mass increase in frequency across generations of calves. (correct answer)
2. Each calf develops greater muscle mass because ranchers chose muscular bulls as parents.
3. New alleles for greater muscle mass arise because selection creates beneficial mutations.
4. Allele frequencies stay constant because only the environment determines muscle mass.
5. The cattle population becomes genetically identical because selection removes all variation.

Explanation: This question assesses the skill of analyzing artificial selection by examining how human-directed breeding changes trait distributions in populations over generations. The correct answer is choice A because ranchers selectively breed only the most muscular bulls, leading to calves inheriting alleles that promote greater muscle mass, and over 10 years, these alleles increase in frequency as less muscular individuals are excluded from reproduction, aligning with the AP Biology concept that artificial selection alters allele frequencies by favoring heritable traits. The stimulus specifies that muscle mass is heritable and varies continuously, indicating polygenic inheritance, where nonrandom mating increases the prevalence of favorable allele combinations in the gene pool. Since calves are raised similarly, environmental factors are controlled, confirming that the shift in average muscle mass results from genetic changes due to selection pressure. A tempting distractor is choice C, which is incorrect due to the misconception of teleology, suggesting selection creates mutations to meet needs rather than acting on existing variation. To approach similar questions, identify how selection acts on pre-existing genetic variation to shift allele frequencies without introducing new mutations or individual adaptations.

Question 7

1. Allele H increases in frequency because individuals with allele H contributed more offspring to the next generations. (correct answer)
2. Allele h increases in frequency because selection favors maintaining both alleles at equal frequencies over time.
3. New H alleles arise during breeding because selection causes mutations that improve egg production.
4. Each chicken develops allele H during its lifetime in response to higher egg-laying conditions.
5. Egg production rises because the population needs more eggs, causing H to appear in most individuals.

Explanation: This question tests your ability to analyze artificial selection and its effects on allele frequencies in populations. In this chicken breeding scenario, the breeder allows only the highest-producing 20% to reproduce, which means individuals with allele H (higher production) are overrepresented among parents compared to their frequency in the general population. This differential reproduction causes allele H to increase in frequency over generations because H-carrying individuals contribute more gametes to the gene pool, shifting the population from 35% to 70% high producers. Option B incorrectly suggests balancing selection, which would maintain both alleles rather than increase one; option C commits the misconception that selection causes beneficial mutations rather than acting on existing variation; options D and E represent Lamarckian errors where individuals acquire or develop traits during their lifetime. When analyzing artificial selection problems, identify which individuals reproduce more and trace how this differential reproduction changes allele frequencies across generations.

Question 8

1. Allele M increased because bulls with M were overrepresented among parents, shifting allele frequencies in offspring. (correct answer)
2. Allele M increased because calves needed more muscle mass, so more M alleles formed during growth.
3. Allele M increased because selection directly changed m alleles into M alleles in fertilized eggs.
4. Allele M increased because allele frequencies automatically move toward 0.75 in any large population.
5. Allele M increased because using a few bulls increases mutation rates that generate more M alleles.

Explanation: This question examines artificial selection through selective breeding in cattle using artificial insemination. When only the top 5% of bulls for muscle mass serve as fathers, bulls carrying allele M are dramatically overrepresented among parents, causing their alleles to dominate the gene pool and increasing M's frequency from 0.30 to 0.75 in just 10 years. This exemplifies how artificial selection works: individuals with desired traits contribute disproportionately more alleles to future generations through differential reproduction. Option B incorrectly suggests alleles form in response to need (Lamarckian error); option C wrongly claims selection directly converts alleles; option D misunderstands allele frequency dynamics; option E incorrectly links breeding practices to mutation rates. To analyze artificial selection scenarios, identify which individuals reproduce and calculate how this skews allele transmission to offspring.

Question 9

1. The frequency of allele R increased because plants producing red kernels contributed more seeds to the next generation. (correct answer)
2. The frequency of allele R increased because plants sensed selection and converted r alleles into R alleles.
3. The frequency of allele R increased because saving seeds causes new R mutations to occur more often.
4. The frequency of allele R increased because allele frequencies change only in response to environmental stress.
5. The frequency of allele R increased because the population required red kernels, so most offspring became red.

Explanation: This question examines artificial selection in crop breeding through seed saving practices. When the farmer saves seeds only from plants with the reddest kernels, plants carrying allele R contribute disproportionately more seeds (and thus alleles) to the next generation, causing R's frequency to increase and shifting the population from 40% to 85% red-kernel plants over four cycles. This demonstrates how human selection of parents based on phenotype drives evolutionary change in agricultural populations. Option B incorrectly suggests plants can sense and respond by converting alleles (Lamarckian misconception); option C wrongly links seed saving to mutation rates; option D misunderstands selection triggers; option E commits a teleological error about population requirements driving inheritance. When analyzing agricultural selection, trace how choosing certain plants as seed sources changes allele frequencies in subsequent plantings.

Question 10

1. Directional selection in Line 1 reduced allelic diversity at ear-length loci compared with the randomly bred Line 2. (correct answer)
2. Random mating in Line 2 caused individuals to change from allele l to L when exposed to longer-eared parents.
3. Line 1 gained variation because selection increases recombination rates that create new ear-length alleles.
4. Line 2 lost variation because random mating prevents alleles from being passed to offspring consistently.
5. Line 1 narrowed variation because rabbits evolved longer ears within their lifetimes before reproducing.

Explanation: This question analyzes how artificial selection affects genetic variation compared to random mating. Line 1 experiences directional selection for long ears, which increases the frequency of allele L while decreasing l, reducing allelic diversity and narrowing the phenotypic range as the population becomes more genetically uniform at ear-length loci. In contrast, Line 2 maintains both alleles through random mating, preserving genetic variation and a wider range of ear lengths. Option B incorrectly suggests individuals change alleles (Lamarckian error); option C wrongly claims selection increases variation through recombination; option D misunderstands random mating's effect on allele transmission; option E represents within-lifetime change rather than population evolution. To compare selection regimes, recognize that directional selection reduces variation while random mating maintains it.

Question 11

1. Genetic variation decreases because alleles associated with shorter ears contribute fewer offspring over generations. (correct answer)
2. Genetic variation increases because selecting one trait always creates new alleles at that locus.
3. Genetic variation stays identical because selection changes only the appearance of ears, not alleles.
4. Genetic variation increases because all rabbits adjust their alleles toward R when handled by humans.
5. Genetic variation decreases only if mutations stop occurring, which selection cannot influence.

Explanation: This question assesses the analysis of artificial selection, where humans selectively breed organisms for desired traits, leading to changes in population genetics. The correct answer is A because selecting rabbits with long ears favors allele R, so alleles associated with shorter ears (r) contribute fewer offspring, decreasing genetic variation and leading to fewer ear-length categories after seven generations. This results in increased average ear length but reduced diversity, as selection erodes variation at the locus. This demonstrates AP Biology concepts of genetic variation and selection, where artificial breeding can narrow the gene pool for a trait. A tempting distractor is D, which is incorrect due to the misconception of directed evolution, suggesting all individuals adjust alleles in response to handling instead of differential reproduction. A transferable strategy for this question type is to assess impacts on genetic variation by considering how selection reduces the frequency of disfavored alleles over time.

Question 12

1. Allele p increases because selection favors rare alleles to preserve diversity in the population.
2. Allele P increases because plants carrying P contribute a larger fraction of the next generation's seeds. (correct answer)
3. Allele frequencies do not change because selecting seeds changes only the environment of kernels.
4. Allele P appears only in plants that eat more nitrogen, so its frequency depends on fertilizer.
5. Each plant adjusts its genotype to Pp when grown in high-protein soil, increasing heterozygosity.

Explanation: This question assesses the analysis of artificial selection, where humans selectively breed organisms for desired traits, leading to changes in population genetics. The correct answer is B because the farmer saves seeds from high-protein plants, which are associated with allele P, allowing these plants to contribute a larger fraction of seeds, thereby increasing P frequency from 0.25 over ten generations. This causes nearly all plants to show high protein content and fewer low-protein plants, as the selection pressure favors P-carrying genotypes. This embodies AP Biology concepts of allele frequency change under selection, where artificial practices mimic evolutionary mechanisms to enhance desired traits. A tempting distractor is E, which is incorrect due to the misconception of genotype plasticity, suggesting plants adjust their genotypes in response to soil rather than selection acting on fixed genetic variation. A transferable strategy for this question type is to link the selected trait to its genetic basis and track how differential seed contribution alters allele frequencies across generations.

Question 13

1. Radish individuals changed their alleles during growth in response to being measured and selected.
2. Alleles contributing to larger root diameter became more common due to nonrandom breeding. (correct answer)
3. Root diameter increased because selection directly increased mutation rate at root-size genes.
4. Root diameter shifted because all plants received more resources in later generations.
5. The shift occurred because plants produced larger roots to meet the breeder's needs.

Explanation: This question assesses the skill of analyzing artificial selection by evaluating how repeated breeding from selected individuals shifts phenotypic distributions in plant populations. The correct answer is choice B because the breeder plants seeds only from the largest 5% of roots each generation, causing alleles that contribute to larger root diameter to be passed on more frequently, resulting in a shift toward larger values over six generations, consistent with the AP Biology principle that artificial selection increases the frequency of advantageous alleles through nonrandom reproduction. The stimulus notes constant environmental conditions like fertilizer and spacing, isolating genetic changes as the cause of the distribution shift. Since root diameter is a quantitative trait, selection on extremes progressively enriches the population for alleles promoting larger sizes. A tempting distractor is choice E, which is incorrect due to the misconception of teleology, implying plants purposefully produce larger roots to fulfill the breeder's goals rather than selection acting on heritable variation. To approach similar questions, distinguish between genetic inheritance across generations and non-heritable changes within individuals, focusing on allele frequency shifts.

Question 14

1. Trout began maturing earlier because individuals adapted their physiology to farm schedules.
2. Alleles associated with earlier maturity increased in frequency due to nonrandom parent choice. (correct answer)
3. Earlier maturity spread because selection caused directed mutations toward early-maturity alleles.
4. The age at maturity decreased because the environment, not heredity, controls maturation timing.
5. Allele frequencies remained constant because only phenotype, not genotype, is affected by selection.

Explanation: This question assesses the skill of analyzing artificial selection by examining shifts in maturation timing through selective breeding in aquatic species. The correct answer is choice B because managers choose only the youngest-maturing trout as parents, increasing the frequency of alleles for earlier maturity over 12 generations, as described in the AP Biology framework where artificial selection amplifies heritable traits via differential reproductive success. The stimulus indicates a lower average age at maturity compared to the original population, attributing this to nonrandom fertilization favoring early-maturing genotypes. With a consistent breeding population of 1,000, the genetic basis of maturation timing leads to evolutionary change under selection. A tempting distractor is choice A, which is incorrect due to a level-of-organization error, attributing changes to individual physiological adaptations rather than population-level allele frequency shifts. To approach similar questions, evaluate how selection criteria influence which genotypes contribute to future generations, predicting trait distributions accordingly.

Question 15

1. Alleles for high protein decrease because selection reduces the need for those alleles.
2. Alleles for high protein increase because selected plants contribute disproportionately to the next generation. (correct answer)
3. Alleles for high protein appear because the farmer's selection directly creates beneficial alleles.
4. Allele frequencies do not change because protein content is acquired from soil nutrients only.
5. Allele frequencies change because individual wheat plants alter their DNA when seeds are saved.

Explanation: This question assesses the skill of analyzing artificial selection by investigating allele frequency changes for nutritional traits in agricultural crops. The correct answer is choice B because saving seeds only from high-protein wheat plants allows those alleles to be disproportionately represented in subsequent generations, increasing average protein content, as per the AP Biology principle that selection amplifies heritable variation through biased reproduction. The stimulus describes multiple generations of selection leading to higher protein, with discarded seeds preventing low-protein alleles from persisting. Protein content as a genetically influenced trait shifts via this process. A tempting distractor is choice E, which is incorrect due to a level-of-organization error, confusing individual DNA alterations with population-level selection on existing variation. To approach similar questions, trace how selective seed saving mimics natural selection in changing allele frequencies over generations.

Question 16

1. Individual plants became shorter by using fewer resources, then passed that acquired trait to offspring.
2. The breeder's choice increased the reproductive contribution of plants carrying allele t. (correct answer)
3. Selection directly converted allele T into allele t within the genomes of tall plants.
4. Allele frequencies stayed constant because only the environment, not heredity, affected height.
5. New mutations for tallness accumulated, making very tall plants rarer over time.

Explanation: This question assesses the analysis of artificial selection, where humans selectively breed organisms for desired traits, leading to changes in population genetics. The correct answer is B because the breeder saves seeds only from the shortest plants, which carry more allele t for shorter height, thereby increasing the reproductive contribution of t-carrying genotypes across eight generations. This results in most plants being short and very tall plants becoming rare, as the frequency of t rises from 0.30 due to the consistent selection against taller phenotypes influenced by T. This demonstrates AP Biology principles of directional selection, where human intervention shifts the population's trait distribution by favoring one extreme of a heritable variation. A tempting distractor is A, which is incorrect due to the misconception of inheritance of acquired characteristics, implying plants actively become shorter and pass that on, confusing environmental effects with genetic heredity. A transferable strategy for this question type is to trace how repeated selection for a trait alters allele frequencies by enhancing the reproduction of specific genotypes, rather than assuming direct environmental or mutational changes.

Question 17

1. Both lines retain identical allele frequencies because they began from the same original population.
2. Allele frequencies diverge between lines because different phenotypes are repeatedly chosen to reproduce. (correct answer)
3. Allele frequencies converge because isolation causes the same allele to become common in both lines.
4. Allele frequencies change only in Line 2 because recessive alleles respond more to selection.
5. Both lines change color without allele-frequency change because selection alters pigments directly.

Explanation: This question assesses the analysis of artificial selection, where humans selectively breed organisms for desired traits, leading to changes in population genetics. The correct answer is B because the two lines are selected for opposite flower colors—red in Line 1 and white in Line 2—causing allele frequencies to diverge as R increases in Line 1 and r in Line 2 over generations. This leads to each line showing mostly one color and few intermediates, due to the isolated, directional selection on the R/r locus. This illustrates AP Biology concepts of divergence and selection, where different pressures on isolated populations result in genetic differentiation. A tempting distractor is E, which is incorrect due to the misconception of level-of-organization error, confusing phenotypic changes with direct pigment alteration rather than underlying allele frequency shifts. A transferable strategy for this question type is to compare allele frequencies across selected groups by noting how opposing selections drive divergence in isolated lines.

Question 18

1. Small-comb birds developed larger combs during life and then produced offspring with larger combs.
2. The breeding program increased the relative reproductive success of genotypes associated with allele G. (correct answer)
3. Large combs caused allele G to form spontaneously in embryos, increasing its frequency each year.
4. Comb size changed because the population needed larger combs to survive, so allele G rose.
5. Allele frequencies could not change because the same chickens remained alive throughout the program.

Explanation: This question assesses the analysis of artificial selection, where humans selectively breed organisms for desired traits, leading to changes in population genetics. The correct answer is B because breeders choose birds with large combs, associated with allele G, increasing the reproductive success of G-carrying genotypes and making small-comb birds rare over years. This shifts the comb-size distribution as G becomes more prevalent in the population. This reflects AP Biology ideas of heritable variation and selection, where human choices drive phenotypic changes through genetic mechanisms. A tempting distractor is D, which is incorrect due to the misconception of teleology, implying populations evolve traits because they 'need' them rather than through differential success of existing variants. A transferable strategy for this question type is to explain trait shifts by focusing on enhanced reproduction of selected genotypes, avoiding purpose-driven interpretations.

Question 19

1. Genetic variation at the locus decreases because allele b becomes rarer when carriers contribute fewer offspring. (correct answer)
2. Genetic variation increases because selection creates new b alleles in response to reduced brown coats.
3. Genetic variation stays constant because allele frequencies cannot change without migration into the population.
4. Genetic variation increases because each dog can alter its genotype from b to B during development.
5. Genetic variation stays high because the population maintains allele b to ensure future adaptability by intention.

Explanation: This question tests understanding of how artificial selection affects genetic variation at a locus. By selecting only black-coated dogs (BB or Bb genotypes) as parents, the breeder reduces the frequency of allele b from 0.45 to 0.12 because brown dogs (bb) never reproduce, and heterozygotes (Bb) contribute fewer b alleles than expected under random mating. This directional selection decreases genetic variation at the coat color locus as one allele becomes increasingly rare. Option B incorrectly suggests selection creates new alleles; option C wrongly claims allele frequencies cannot change without migration; option D represents a Lamarckian error of individual genotype change; option E commits a teleological fallacy about maintaining variation for future needs. When analyzing selection's effect on variation, remember that consistently selecting for one phenotype reduces allelic diversity by making alternative alleles rarer.

Question 20

1. Allele c increases because curly-winged flies produce c alleles through repeated wing use.
2. Allele C increases because flies with curly wings contribute disproportionately to the next generation. (correct answer)
3. Allele frequencies remain constant because selecting phenotypes cannot alter the gene pool.
4. Allele c increases because selection always favors recessive alleles over dominant alleles.
5. Allele frequencies change only if flies migrate into the lab population from the wild.

Explanation: This question assesses the analysis of artificial selection, where humans selectively breed organisms for desired traits, leading to changes in population genetics. The correct answer is B because only curly-winged flies reproduce, favoring allele C for curly wings, so these flies contribute disproportionately, increasing C frequency and making straight-winged flies rare over generations. Starting from f(c)=0.70, the shift occurs as selection reduces the representation of c in the population. This aligns with AP Biology principles of directional selection, where human intervention reduces variation by promoting dominant phenotypes. A tempting distractor is A, which is incorrect due to the misconception of use-disuse inheritance, implying wings produce alleles through use rather than selection on pre-existing genetic differences. A transferable strategy for this question type is to identify the favored allele and predict its increase through enhanced reproduction, distinguishing it from non-Darwinian mechanisms.