AP Biology Quiz: Common Ancestry

What this quiz covers

This quiz focuses on Common Ancestry, 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. Chickens and lizards share a common amniote ancestor that had similar early developmental patterning. (correct answer)
2. Chickens evolved from lizards because chicken embryos pass through a lizardlike stage.
3. The shared embryonic traits arose independently because embryos develop similarly in all environments.
4. The shared embryonic traits show that adult chickens and adult lizards are more similar than either is to other reptiles.
5. The regulatory genes are identical in function, so the two lineages must be equally related to all vertebrates.

Explanation: This question requires inferring common ancestry from shared embryonic features and gene expression patterns. The presence of pharyngeal arches, segmented tail buds, and similar regulatory gene expression in both chicken and lizard embryos indicates these features were inherited from their common amniote ancestor, even though adult forms differ significantly. These complex developmental similarities are best explained by common descent rather than convergence. Choice B incorrectly assumes one lineage evolved from the other based on embryonic similarities, confusing shared ancestry with direct descent. When comparing developmental patterns, recognize that shared embryonic features and gene expression indicate inheritance from a common ancestor possessing those developmental programs.

Question 2

1. The modern horse lineage and the fossil lineage share a common ancestor with that distinctive molar pattern. (correct answer)
2. The fossil is a direct ancestor of the modern horse because it occurs in older rock layers.
3. The molar pattern evolved independently in multiple mammals because triangular cusps are universally optimal.
4. The modern horse is more closely related to all mammals with small teeth than to mammals with large teeth.
5. The fossil lineage is more closely related to mammals lacking the cusp pattern because its face is shorter.

Explanation: This question requires inferring common ancestry from shared fossil and modern anatomical features. The identical molar cusp pattern (three cusps in a specific triangular arrangement with a groove between the second and third cusp) shared by the modern horse and fossil mammal indicates they inherited this complex trait from a common ancestor, especially since other mammals in the same deposits lack this pattern. The specific structural details make independent evolution unlikely. Choice B incorrectly assumes the fossil is a direct ancestor simply because it's older, confusing shared ancestry with direct lineage. When comparing fossil and modern forms, recognize that shared complex anatomical features indicate common ancestry rather than direct ancestor-descendant relationships.

Question 3

1. Hawks and eagles share a more recent common ancestor with each other than either shares with sparrows or penguins. (correct answer)
2. Penguins and sparrows are the closest relatives because both differ from raptors by many sites.
3. All four bird lineages are equally related because they share a mitochondrial gene of the same length.
4. Sparrows are ancestral to hawks because sparrows have more sequence differences from penguins.
5. Hawks and penguins independently evolved similar mitochondrial sequences due to similar body size.

Explanation: This question tests inferring common ancestry from mitochondrial sequence differences among bird species. Hawks and eagles show only 6 sequence differences, while both differ from sparrows by 44-46 sites and from penguins by 62-63 sites, indicating hawks and eagles share a more recent common ancestor with each other than either shares with sparrows or penguins. This pattern reflects the evolutionary relationships among these bird groups, with raptors (hawks and eagles) forming a distinct clade. Choice B incorrectly groups penguins and sparrows based on their similar distances from raptors, missing that they differ from each other by 60 sites. When analyzing sequence data, focus on pairwise differences between species - smaller differences indicate more recent common ancestry.

Question 4

1. The four species share a common ancestor with the same basic forelimb bone pattern. (correct answer)
2. The four species independently evolved identical bones because they all need to move.
3. The limbs have similar functions, so the species are more closely related than other mammals.
4. The bone similarities show that the species recently exchanged genes through hybridization.
5. The limbs became similar because the environment caused the same bones to form in each lineage.

Explanation: This question tests the skill of inferring common ancestry from shared anatomical traits. The similar arrangement of bones in the forelimbs of bats, whales, cats, and humans suggests these structures are homologous, inherited from a common ancestor that possessed the same basic bone pattern. Despite differences in bone proportions and limb functions, the consistent relative order of humerus, radius, ulna, carpals, metacarpals, and phalanges indicates divergence from a shared ancestral form rather than independent origins. This shared-trait reasoning supports that the four species evolved from a common ancestor with this forelimb blueprint, which was later modified for different uses. A tempting distractor is choice B, which incorrectly attributes the similarities to convergent evolution, a misconception that confuses homology with analogy based on function alone. To infer common ancestry in similar scenarios, compare structural patterns while considering if they reflect inheritance rather than environmental convergence.

Question 5

1. Mammal and reptile lineages share common ancestry in which homologous bones were modified over time. (correct answer)
2. Mammals acquired their ear bones from reptiles through horizontal gene transfer between lineages.
3. Mammals and reptiles are unrelated because the bones serve different functions in each lineage.
4. The similar bones formed independently because similar environments produce the same bone shapes.
5. Reptiles descended from mammals because mammals have a greater number of ear bones.

Explanation: This question assesses the skill of inferring common ancestry from homologous bone arrangements in mammal ears and reptile jaws. The correspondence between mammalian middle ear bones (malleus, incus) and reptilian jaw bones (articular, quadrate), supported by developmental studies showing shared embryonic origins, indicates inheritance and modification from a common ancestor. This homology suggests that mammal and reptile lineages diverged from a shared tetrapod ancestor, with bones repurposed for hearing in mammals over evolutionary time. The positional and shape similarities further reinforce that these are not independent structures but evolved from the same ancestral bones. A tempting distractor is choice D, which claims independent formation due to environments, but this ignores developmental and positional evidence, embodying a convergence misconception. To infer common ancestry from homologous structures, trace developmental and fossil origins, using them to map trait modifications across related lineages.

Question 6

1. Modern whales share common ancestry with terrestrial mammal lineages that possessed hindlimbs and a pelvis. (correct answer)
2. Whales acquired pelvic bones through hybridization with terrestrial mammals after whales became fully aquatic.
3. Whale pelvic bones are analogous to mammal pelvises because they arose from different ancestral structures.
4. Terrestrial mammals evolved from whales because whale fossils show reduced hindlimbs in younger rocks.
5. Whale pelvic bones persist because they are required for walking on land during reproduction.

Explanation: This question assesses the skill of inferring common ancestry from vestigial structures and fossil evidence in whales. The small, internal pelvic bones in modern whales, homologous to those attached to hindlimbs in terrestrial mammals, indicate inheritance from a common ancestor with functional hindlimbs that were reduced in aquatic lineages. Fossil sequences showing progressive hindlimb reduction while retaining pelvic structures support that whales share ancestry with terrestrial mammals, with the trait becoming vestigial over time. This homology, combined with positional and compositional similarities, points to a shared evolutionary origin rather than convergence. A tempting distractor is choice C, which labels the structures analogous, but this misconception dismisses the fossil and structural evidence of shared ancestry and homologous development. To infer common ancestry from vestigial traits, examine fossil transitions and compare to functional homologs in relatives, using them to trace evolutionary modifications.

Question 7

1. Species T shares the most recent common ancestor with species R because both have chloroplast DNA.
2. Species R and S share a more recent common ancestor lineage than either shares with species T. (correct answer)
3. Species T is a direct ancestor of R and S because its sequence identity is lower.
4. All three species are equally related because chloroplasts perform photosynthesis in each lineage.
5. Species R and S evolved similar chloroplast sequences independently due to similar light environments.

Explanation: This question assesses the skill of inferring common ancestry from chloroplast DNA sequence similarities in plants. The high sequence identity (99.2%) between flowering plants R and S, compared to their lower identity (~93%) with moss T, indicates that R and S share a more recent common ancestor than either does with T. This pattern suggests that mutations accumulated more in the lineages leading to T after divergence, while R and S retained greater similarity due to closer relatedness. The presence of the region in all three supports inheritance from a shared photosynthetic ancestor, with degrees of similarity revealing branching order. A tempting distractor is choice E, which attributes similarities to independent evolution from environments, but this convergent misconception overlooks the improbability of such high identity arising separately. To infer common ancestry from organelle DNA, calculate sequence identities and interpret higher values as signs of more recent divergence, aiding in reconstructing plant phylogenies.

Question 8

1. Species A and C share the most recent common ancestor because both possess Hox genes.
2. Species A and B share a more recent common ancestor lineage than either shares with species C. (correct answer)
3. Species C is ancestral to A and B because its Hox cluster is arranged differently.
4. Species A and B evolved similar Hox clusters independently because they develop similar body plans.
5. All three species diverged at the same time because Hox genes are conserved in animals.

Explanation: This question assesses the skill of inferring common ancestry from the arrangement and sequence similarity of Hox genes in animals. The identical gene order and high sequence similarity between species A and B indicate they inherited their Hox clusters from a more recent common ancestor than either shares with species C, which has a different order and lower similarity. This conservation of complex gene arrangements suggests shared developmental pathways passed down from a common lineage, with divergence leading to the differences seen in C. The pattern reflects evolutionary history, where closer relatives retain more similar genetic architectures. A tempting distractor is choice D, which posits independent evolution of similar clusters, but this underestimates the improbability of converging on identical complex arrangements and ignores inheritance as the simpler explanation. To infer common ancestry from genetic data, compare both sequence identity and structural organization, using higher similarity to identify more recent shared lineages.

Question 9

1. The four species inherited the forelimb bone pattern from a common tetrapod ancestor lineage. (correct answer)
2. The four species independently evolved identical limb patterns because they occupy similar habitats.
3. The four species share limb bones because natural selection produces the same structures in all animals.
4. The four species are most closely related to birds because both groups have forelimbs used for movement.
5. The limb similarities result from recent gene flow among the four species after they diverged.

Explanation: This question assesses the skill of inferring common ancestry from anatomical, embryological, and fossil evidence. The shared forelimb bone pattern among humans, cats, whales, and bats suggests these species inherited the trait from a common tetrapod ancestor, as the identical arrangement indicates homology rather than independent evolution. Embryological similarities in tissue buds further support that the limbs develop from conserved developmental pathways inherited from a shared lineage. Fossil evidence of early tetrapods with the same pattern reinforces that this trait was present in their common ancestor and modified over time in descendant lineages. A tempting distractor is choice B, which attributes the similarities to convergent evolution due to similar habitats, but this ignores the homologous bone arrangement and embryological data that point to inheritance rather than independent origins. To infer common ancestry effectively, look for homologous structures supported by multiple lines of evidence like fossils and development, as greater similarity in complex traits often indicates shared evolutionary history.

Question 10

1. Species M and N share a more recent common ancestor lineage than species M shares with O or P. (correct answer)
2. Species O is the direct ancestor of species P because their sequences are most different from M.
3. All four species are equally related because cytochrome c has the same function in each.
4. Species P is most closely related to M because larger differences indicate earlier divergence.
5. Species N and O are most closely related because their sequences must be identical to function.

Explanation: This question assesses the skill of inferring common ancestry from protein sequence differences in cytochrome c among vertebrates. The minimal differences between species M and N (2 amino acids) compared to M-O (11) and M-P (14) suggest M and N share a more recent common ancestor, as fewer changes have accumulated since their divergence. The conserved function of cytochrome c across species indicates that sequence similarities reflect inheritance from a shared lineage rather than convergence. This pattern allows inference of relative divergence times, with greater similarity pointing to closer relatedness. A tempting distractor is choice C, which assumes equal relatedness due to shared function, but this overlooks how sequence divergence quantifies ancestry and misapplies functional conservation to relatedness. To infer common ancestry from molecular data, compare sequence similarities quantitatively, remembering that fewer differences typically indicate more recent shared ancestry across lineages.

Question 11

1. The lizard and bird share a more recent common ancestor with each other than either shares with the salamander. (correct answer)
2. The lizard and bird evolved the fused ankle because they both needed to walk on land.
3. The salamander is more closely related to the bird because both have a vertebral column.
4. The fused ankle shows that lizards are direct ancestors of modern birds in a single unbranched lineage.
5. All three species are equally related because they share a skull and vertebral column.

Explanation: This question tests the skill of inferring common ancestry from shared skeletal traits. The fused ankle bone unique to the lizard and bird, alongside broadly shared features like the vertebral column and skull, suggests the lizard and bird inherited this fusion from a more recent common ancestor not shared with the salamander. This shared-trait reasoning identifies the fusion as a derived homology (synapomorphy) indicating a closer branching point between lizard and bird lineages. Therefore, the observations support greater relatedness between lizard and bird relative to the salamander. A tempting distractor is choice E, which assumes equal relatedness from basal traits, a misconception of overlooking derived characters for finer phylogenetic resolution. To infer common ancestry from skeletons, distinguish between ancestral and derived traits to pinpoint more recent shared ancestors.

Question 12

1. Species M and N share a more recent common ancestor with each other than either shares with Species P. (correct answer)
2. Species P is the descendant of Species M because it lacks the insertion found in M.
3. Species M and N independently acquired identical insertions because they experienced similar environments.
4. All three species are equally related because they all have DNA at the genomic site.
5. Species M and N have the insertion because the transposable element inserted to increase fitness in both lineages.

Explanation: This question tests the skill of inferring common ancestry from shared genomic features. The identical transposable element insertion at the same site in Species M and N, absent in P, suggests M and N inherited this from a common ancestor after diverging from P's lineage. This shared-trait reasoning treats the insertion as a rare, derived event marking a specific clade, with matching boundaries confirming a single origin. Thus, the data support M and N sharing a more recent common ancestor than with P. A tempting distractor is choice C, which attributes the similarity to independent events, a misconception of convergence ignoring the improbability of identical insertions. To infer common ancestry from genomes, identify unique shared mutations like insertions as evidence of descent from a common ancestor post-event.

Question 13

1. Humans and orangutans share the most recent common ancestor because they show the most differences.
2. Humans and chimpanzees share a more recent common ancestor than humans and gorillas do. (correct answer)
3. All four species are unrelated because their sequences are not identical.
4. Gorillas are direct ancestors of humans because their sequences are intermediate.
5. The gene evolved to be similar in humans and chimpanzees because both species live in forests.

Explanation: This question tests the skill of inferring common ancestry from genetic differences. The minimal nucleotide differences between humans and chimpanzees (1) compared to humans-gorillas (6) and humans-orangutans (18) indicate humans and chimpanzees share a more recent common ancestor. This shared-trait reasoning uses the molecular clock concept, where fewer mutations accumulate between closely related species due to shorter divergence time. Thus, the data support closer relatedness between humans and chimpanzees, with gorillas branching off earlier. A tempting distractor is choice A, which misreads greater differences as indicating recency, a misconception that reverses the logic of similarity equating to closer ancestry. To infer common ancestry from genes, compare sequence divergences and associate smaller differences with more recent shared ancestors.

Question 14

1. Humans and chimpanzees share a more recent common ancestor with each other than either shares with gorillas. (correct answer)
2. Gorillas and humans share a more recent common ancestor because both are large-bodied primates.
3. Chimpanzees are ancestral to humans because they retain an insertion that humans later lost.
4. All three lineages are equally related because introns do not affect phenotype.
5. Humans and gorillas independently acquired different changes at the same site due to similar diets.

Explanation: This question tests inferring common ancestry from shared genetic insertions in neutral DNA regions. The identical 120-base-pair insertion at the same position in both human and chimpanzee introns, absent in gorillas, indicates humans and chimpanzees share a more recent common ancestor with each other than either shares with gorillas. Since introns are selectively neutral, this shared insertion is extremely unlikely to have arisen independently and instead represents a single insertion event in their common ancestor. Choice C incorrectly interprets the insertion as an ancestral trait that humans lost, misunderstanding that both species share the derived state. When analyzing neutral genetic markers like intron insertions, shared derived traits at identical positions provide strong evidence for recent common ancestry.

Question 15

1. Lineages X and Y share a more recent common ancestor with each other than either shares with the other lineages. (correct answer)
2. Lineages X and Y evolved fused petals independently because tubular corollas attract the same pollinators.
3. Lineage X is ancestral to lineage Y because X and Y differ by only a few substitutions.
4. All five lineages are equally related because each lineage contains petals and vascular tissue.
5. The other three lineages are closest relatives because they share separate petals and therefore the original condition.

Explanation: This question requires inferring common ancestry from multiple lines of evidence - morphology and molecular data. Lineages X and Y share both fused petals with an unusual vascular bundle arrangement and differ by only 3 chloroplast substitutions, while differing from other lineages by over 40 substitutions, strongly supporting that X and Y share a more recent common ancestor. The combination of shared complex morphology and low genetic divergence makes independent evolution extremely unlikely. Choice B incorrectly assumes convergent evolution despite the genetic evidence, failing to integrate both data types. When multiple independent lines of evidence (morphological and molecular) point to the same relationship, this provides particularly strong support for common ancestry.

Question 16

1. The lineages share a common tetrapod ancestor that had the same basic forelimb bone pattern. (correct answer)
2. The lineages evolved identical bone arrangements independently because the environment favors five-part limbs.
3. Bats and whales are the most closely related because both use their forelimbs to move through a fluid.
4. Cats are ancestral to bats because cat forelimbs contain the same bones but are less specialized.
5. Lizards are equally related to all mammals because all four lineages have forelimbs with phalanges.

Explanation: This question requires inferring common ancestry from shared anatomical structures across diverse vertebrates. The identical bone arrangement (humerus, radius, ulna, carpals, metacarpals, phalanges) in the same relative order across bat, whale, cat, and lizard forelimbs indicates inheritance from a common tetrapod ancestor, despite their different functions today. This homologous structure pattern is strong evidence for common descent rather than independent evolution. Choice B incorrectly assumes convergent evolution would produce identical bone arrangements, when convergence typically produces similar functions through different structures. When examining shared anatomical features, recognize that complex structural similarities in the same relative positions indicate common ancestry rather than independent origins.

Question 17

1. The two lineages sharing the insertion have a more recent common ancestor than either does with the third lineage. (correct answer)
2. The third lineage is ancestral to the other two because it lacks the insertion and therefore is less derived.
3. All three lineages are equally related because the same locus is present in each lineage.
4. The insertion evolved independently in the two lineages because both occupy similar ecological niches.
5. The two lineages sharing the insertion are more distantly related because insertions increase genetic distance.

Explanation: This question tests inferring common ancestry from rare genomic events like transposable element insertions. Two insect lineages sharing the same transposable element at an identical genomic location, while a third lineage lacks it, indicates the two lineages with the insertion share a more recent common ancestor than either does with the third lineage. Identical insertions are extremely rare events unlikely to occur independently, making shared ancestry the best explanation. Choice D incorrectly invokes convergent evolution for a molecular marker that has no functional significance, ignoring the extreme improbability of independent identical insertions. When analyzing rare genomic events like transposon insertions, recognize that sharing such events at identical positions provides strong evidence for recent common ancestry.

Question 18

1. Seals and bears share a more recent common ancestor with each other than either shares with wolves. (correct answer)
2. Seals and wolves are the closest relatives because both can occupy aquatic environments at times.
3. Bears are ancestral to seals because bears retain more terrestrial traits than seals.
4. All three lineages are equally related because each lineage contains a pseudogene with stop codons.
5. The shared stop codon arose independently in seals and bears due to similar diets and metabolism.

Explanation: This question tests inferring common ancestry from shared mutations in nonfunctional DNA. Seals and bears sharing the same premature stop codon at an identical position in a pseudogene, while wolves have a different stop codon elsewhere, indicates seals and bears share a more recent common ancestor with each other than either shares with wolves. Since pseudogenes are nonfunctional, this shared mutation cannot be maintained by selection and must represent a single mutational event in their common ancestor. Choice E incorrectly invokes convergent evolution for a neutral trait, ignoring that selection cannot maintain specific mutations in nonfunctional sequences. When analyzing pseudogenes or other neutral sequences, shared mutations at identical positions provide strong evidence for recent common ancestry.

Question 19

1. Mice and dogs share a more recent common ancestor with each other than either shares with lizards. (correct answer)
2. Lizards and mammals share a more recent common ancestor than mice and dogs because all are vertebrates.
3. Dogs are ancestral to mice because dogs have larger skulls and more robust ear bones.
4. The three-bone middle ear evolved independently in mice and dogs due to similar hearing needs.
5. Mice are more closely related to lizards than to dogs because both have small body size.

Explanation: This question requires inferring common ancestry from shared derived anatomical features. Mice and dogs both possess three middle-ear bones with a distinctive malleus-incus joint, while lizards have only one middle-ear bone and lack this joint, indicating mice and dogs (both mammals) share a more recent common ancestor with each other than either shares with lizards. The three-bone middle ear is a derived mammalian trait inherited from their common ancestor. Choice D incorrectly assumes convergent evolution of this complex anatomical system, ignoring that such detailed structural similarities are better explained by common descent. When comparing anatomical features, recognize that shared derived traits (like the mammalian middle ear) indicate more recent common ancestry than shared primitive traits.

Question 20

1. Species 1 and 2 share a more recent common ancestor than either shares with Species 3 or 4. (correct answer)
2. Species 3 and 4 are more closely related to Species 1 because they retain the longer sequence.
3. Species 1 and 2 are unrelated because the deletion occurs in noncoding DNA.
4. Species 2 is the ancestor of Species 1 because both have the same deletion.
5. The deletion occurred in Species 1 and 2 because the region needed to become shorter over time.

Explanation: This question tests the skill of inferring common ancestry from shared genetic modifications. The exact 12-base deletion in the same noncoding position in Species 1 and 2, absent in 3 and 4, indicates 1 and 2 inherited this deletion from a common ancestor after splitting from the others. This shared-trait reasoning views the deletion as a derived mutation event that occurred once, marking closer relatedness within the 1-2 clade. Therefore, the data support Species 1 and 2 sharing a more recent common ancestor than with 3 or 4. A tempting distractor is choice E, which implies the deletion evolved for a purpose, a misconception of directed evolution rather than random mutation and inheritance. To infer common ancestry from DNA, look for identical mutations in nonfunctional regions as strong indicators of shared descent.