Question 1
A population of insects is studied over 40 generations. What observation would provide direct evidence that evolution has occurred?
A.
The proportion of insects with a heritable wing-colour trait changes in the population.
B.
The average mass of adult insects increases during a single feeding season.
C.
One insect develops larger flight muscles after repeated use of its wings.
D.
Several insects lose parts of their wings after damage from predators.
Question 2
Farmers repeatedly choose rice plants with the largest grains as parents. After many generations, the rice population has a higher mean grain mass. What does this demonstrate?
A.
Artificial selection can change heritable characteristics in a population.
B.
Acquired characteristics are inherited when plants grow in cultivation.
C.
Hybrid sterility increases the yield of domesticated crop plants.
D.
Extinction decreases biodiversity in agricultural ecosystems.
Question 3
The same gene is sequenced in four mammal species. Species P and Q differ at two bases, species P and R differ at 27 bases, and species P and S differ at 31 bases. What conclusion is best supported by these data?
A.
Species P and Q share a more recent common ancestor than P and R.
B.
Species R and S must have identical amino acid sequences in all proteins.
C.
Species P evolved from species Q because their base sequences are similar.
D.
Species P and S are unrelated because their sequences are not identical.
Question 4
The human arm, bat wing and whale flipper contain a humerus, radius, ulna, wrist bones and digits in the same relative order. What is the best evolutionary explanation for this similarity?
A.
They are unrelated structures because they now have different functions.
B.
They are homologous structures inherited from a common ancestor.
C.
They are acquired structures produced by use during an organism's lifetime.
D.
They are analogous structures produced by identical selection pressures.
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Question 5
Bird wings and insect wings are both used for flight, but bird wings are modified vertebrate forelimbs whereas insect wings are outgrowths of the exoskeleton. What process best explains this similarity in function?
A.
Divergent evolution producing homologous structures
B.
Selective breeding producing domesticated structures
C.
Convergent evolution producing analogous structures
D.
Geographical isolation producing acquired structures
Question 6
Two populations of insects live in the same meadow. One population mates at dawn and the other mates at dusk, so interbreeding rarely occurs. What type of speciation is this most likely to promote?
A.
Allopatric speciation by behavioural isolation
B.
Allopatric speciation by geographical isolation
C.
Sympatric speciation by hybrid sterility
D.
Sympatric speciation by temporal isolation
Question 7
A founder population of finches reaches an island group with many vacant niches. Over time, several closely related finch species evolve with different beak forms and feeding habits. How does this pattern affect biodiversity?
A.
Hybridization decreases biodiversity as all finches merge into one gene pool.
B.
Stabilizing selection prevents biodiversity by favouring the same intermediate beak.
C.
Extinction increases biodiversity as species with unsuitable beaks are removed.
D.
Adaptive radiation increases biodiversity as related species specialize in different niches.
Question 8
Two moth species live in the same forest and are active on the same nights. Males of each species respond only to the pheromone released by females of their own species. What is the role of this difference?
A.
It is a prezygotic behavioural barrier that prevents hybridization.
B.
It is a geographical barrier that separates the moth gene pools.
C.
It is a postzygotic barrier that causes sterility in hybrid moths.
D.
It is an example of polyploidy that restores fertility after hybridization.
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Question 9
A population of lizards lives on a small island. Some adult lizards lose parts of their tails during attacks by predators. In the same population, inherited differences in body colour affect survival on different rock surfaces.
State what is meant by evolution.
[1]
Distinguish between tail loss and body colour as examples of change in this population.
[2]
Question 10
An ancestral population of apes in the genus Pan became separated by the Congo River. The populations later diverged into bonobos and common chimpanzees. What combination of processes most likely contributed to this speciation?
A.
Acquired social behaviours were inherited and immediately formed two species.
B.
Geographical isolation increased gene flow and kept both populations genetically similar.
C.
Differential selection caused divergence while unrestricted interbreeding continued.
D.
Geographical isolation reduced gene flow and differential selection changed the populations.
Question 11
What statement correctly compares allopatric and sympatric speciation?
A.
Both require geographical isolation, but only sympatric speciation requires differential selection.
B.
Only sympatric speciation increases biodiversity by producing additional species.
C.
Only allopatric speciation requires reproductive isolation between diverging populations.
D.
Both require reproductive isolation, but only allopatric speciation begins with geographical separation.
Question 12
A mule is usually healthy but sterile. How does mule sterility help maintain the separation between horse and donkey species?
A.
It prevents alleles in the hybrid from being passed to later generations.
B.
It causes horses and donkeys to become geographically isolated.
C.
It prevents fertilization from occurring between horses and donkeys.
D.
It makes the hybrid a fertile new species by chromosome doubling.
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Question 13
The amino acid sequence of the same protein was compared in four mammals. The number of amino acid differences compared with the human sequence is shown.
Mammal | Number of amino acid differences |
|---|---|
Common chimpanzee | 1 |
Gorilla | 3 |
Rhesus monkey | 7 |
House mouse | 25 |
Identify the mammal most closely related to humans, using the sequence comparison.
[1]
Explain how sequence data provides evidence for common ancestry.
[3]
Question 14
Farmers have produced many varieties of maize by repeatedly selecting plants with larger kernels and using them as parents for the next generation.
Outline why selective breeding can be used as evidence for evolution.
[2]
State one difference between selective breeding and natural selection.
[1]
Question 15
The forelimbs of a human, bat and whale have different functions but contain bones arranged in the same relative positions.
Identify the type of evolutionary evidence shown by these forelimbs.
[1]
Explain why the pentadactyl limb provides evidence for evolution.
[3]
Question 16
Bird wings and insect wings both allow flight, but they are built from different tissues and body parts.
State the term for structures such as bird wings and insect wings.
[1]
Explain how convergent evolution can produce these structures.
[2]
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Question 17
Horses and donkeys can mate to produce mules. Most mules are healthy but sterile.
State the type of reproductive barrier shown by mule sterility.
[1]
Explain how sterility of interspecific hybrids helps maintain species boundaries.
[3]
Question 18
A section of the mitochondrial cytochrome b gene was sequenced in five primate species. The table shows the number of base differences between each pair of species in the same aligned section of DNA.
Species | Human | Chimpanzee | Gorilla | Orangutan | Rhesus macaque |
|---|---|---|---|---|---|
Human | 0 | 1 | 4 | 7 | 15 |
Chimpanzee | 1 | 0 | 3 | 7 | 16 |
Gorilla | 4 | 3 | 0 | 6 | 14 |
Orangutan | 7 | 7 | 6 | 0 | 17 |
Rhesus macaque | 15 | 16 | 14 | 17 | 0 |
Identify the species in the table that is most closely related to humans.
[1]
State one pattern shown by the sequence differences among the primates.
[1]
Explain how the sequence data provide evidence for common ancestry.
[2]
Question 19
A plant breeder selected maize plants with the largest kernels as parents for each new generation. Kernel mass was measured in the original population and after several generations of selective breeding.
Describe the change in mean kernel mass over the period shown.
[1]
Identify the selection pressure applied in this breeding programme.
[1]
Explain why this selective breeding is evidence that evolutionary change can occur rapidly.
[2]
Question 20
A sterile hybrid forms between two related species of Persicaria. A whole-genome duplication then occurs in the hybrid. What explains how this could cause abrupt speciation?
A.
Chromosome doubling gives each chromosome a pairing partner, restoring meiosis in the polyploid.
B.
Hybridization causes gradual differential selection without changing chromosome number.
C.
Whole-genome duplication makes the hybrid able to mate freely with both parent species.
D.
Chromosome doubling removes all genetic differences between the two parent species.
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Question 21
Bonobos and common chimpanzees are both in the genus Pan. Their present distributions are separated by the Congo River, which they do not usually cross.
Identify the type of reproductive isolation represented by the Congo River.
[1]
Explain how reproductive isolation and differential selection could have led to divergence of bonobos and common chimpanzees.
[3]
Question 22
Speciation may occur in populations living in different areas or in populations living in the same area.
Distinguish between allopatric and sympatric speciation.
[2]
State two requirements shared by allopatric and sympatric speciation.
[2]
Question 23
Two closely related moth populations live in the same forest. One population releases mating pheromones just after sunset, whereas the other releases pheromones near dawn. Individuals rarely mate between the two populations.
Identify the type of reproductive isolation described.
[1]
Suggest how this isolation could lead to sympatric speciation.
[2]
Question 24
A volcanic island is colonized by a small population of seed-eating birds. After many generations, several related bird species are present on the island, each feeding mainly on a different food source.
State the term for this pattern of evolution.
[1]
Explain how this pattern can increase biodiversity while allowing related species to coexist.
[3]
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Question 25
Two models of speciation are considered. In model 1, isolated animal populations diverge slowly under different selection pressures. In model 2, a plant lineage becomes polyploid after whole-genome duplication.
Compare gradual speciation by divergence with abrupt plant speciation by polyploidy.
[3]
Question 26
The diagrams show the forelimb skeletons of four mammals with different modes of locomotion.
Identify the bone labelled as the single proximal bone in each forelimb.
[1]
Compare the forelimb skeletons shown.
[2]
Explain why these forelimbs are evidence for evolution.
[1]
Question 27
The table compares the wings of three groups of animals that fly.
Animal group | Wing origin | Wing support / surface | Main function |
|---|---|---|---|
Bird | Modified forelimb of a vertebrate | Bones covered with feathers | Flight |
Bat | Modified forelimb of a mammal | Bones with skin membrane between elongated digits | Flight |
Insect | Outgrowth of the body wall / exoskeleton | Thin chitinous wing with veins | Flight |
State whether bird wings and insect wings are homologous or analogous structures.
[1]
Give one reason for your answer to part (a).
[1]
Suggest how convergent evolution could have produced the similarity in function.
[2]
Question 28
The diagram represents the history of a lineage of island lizards over time. Branching events, gradual change in body size and extinction events are indicated.
State the number of living species represented at the present time.
[1]
State the effect of the extinction event on the total number of species.
[1]
Distinguish between gradual evolutionary change and speciation using the diagram.
[2]
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Question 29
Two closely related moth forms occur in the same forest. Adults were trapped through the year and mating responses were tested using pheromone extracts.
Observation | Form 1 adults trapped (no.) | Form 2 adults trapped (no.) | Form 1 males responding to extract (out of 20) | Form 2 males responding to extract (out of 20) |
|---|---|---|---|---|
Jan | 0 | 0 | — | — |
Feb | 1 | 0 | — | — |
Mar | 6 | 0 | — | — |
Apr | 14 | 0 | — | — |
May | 19 | 1 | — | — |
Jun | 13 | 3 | — | — |
Jul | 4 | 11 | — | — |
Aug | 0 | 17 | — | — |
Sep | 0 | 15 | — | — |
Oct | 0 | 7 | — | — |
Nov | 0 | 1 | — | — |
Dec | 0 | 0 | — | — |
Pheromone extract from form 1 | — | — | 19 | 2 |
Pheromone extract from form 2 | — | — | 1 | 18 |
Identify two types of reproductive isolation shown by the data.
[2]
Explain how these isolating mechanisms could lead to sympatric speciation.
[2]
Question 30
Horses and donkeys can interbreed to produce mules. The diagram compares chromosome numbers and the outcome of meiosis in the parent species and in mules.
State the type of reproductive barrier represented by mule sterility.
[1]
Explain why mules are usually sterile.
[2]
Question 31
Some species of knotweed and smartweed in the genus Persicaria are thought to have arisen when two related species hybridized and the chromosome number then doubled.
Identify the type of polyploidy described.
[1]
Explain how hybridization followed by polyploidy can cause abrupt speciation in plants.
[3]
Question 32
Bonobos (Pan paniscus) and common chimpanzees (Pan troglodytes) live on opposite sides of the Congo River. Researchers compared ecological conditions and behavioural traits of populations on the two sides of the river.
Population | Food availability / arb. units | Gorilla competition / arb. units | Aggression score / 10 | Cooperation score / 10 |
|---|---|---|---|---|
North side | 45 | 6 | 8 | 3 |
South side | 70 | 2 | 4 | 7 |
Identify the type of reproductive isolation most directly caused by the Congo River.
[1]
Describe two differences between the populations shown in the data.
[2]
Explain how reproductive isolation and differential selection could have led to divergence of the two populations.
[2]
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Question 33
Researchers studied four closely related fish populations in a chain of crater lakes. Genetic differences, current geographic separation and mating behaviour were recorded.
Pair | Current geography | Breeding sites | Courtship preference / % | Genetic divergence / % |
|---|---|---|---|---|
L1 red × L1 blue | same lake | overlap | 96 | 0.4 |
L1 red × L2 yellow | different lakes | no overlap | 51 | 1.6 |
L1 red × L3 silver | different lakes | no overlap | 49 | 2.0 |
L1 blue × L2 yellow | different lakes | no overlap | 50 | 1.7 |
L1 blue × L3 silver | different lakes | no overlap | 48 | 2.1 |
L2 yellow × L3 silver | different lakes | no overlap | 52 | 0.7 |
Identify one population pair that is most consistent with allopatric speciation and give the evidence.
[2]
Identify one population pair that is most consistent with sympatric speciation and give the evidence.
[2]
Evaluate why the current distribution alone is not sufficient to prove sympatric speciation.
[1]
Question 34
A group of finch species on an island archipelago was studied. Beak measurements, diet and DNA sequence similarity were compared.
Species | Beak length / mm | Beak depth / mm | Main diet | DNA similarity / % |
|---|---|---|---|---|
Finch A | 9 | 8 | small seeds | 98 |
Finch B | 10 | 11 | large hard seeds | 97 |
Finch C | 12 | 7 | fruit and buds | 97 |
Finch D | 13 | 5 | insects | 99 |
Finch E | 15 | 6 | cactus flowers/nectar | 96 |
State the evidence in the figure that the finches are closely related.
[1]
Explain how the beak data support adaptive radiation.
[2]
Explain how adaptive radiation can increase biodiversity in an ecosystem with vacant niches.
[2]
Question 35
Two closely related frog species overlap in part of their range. Researchers recorded courtship calls, mating attempts and the fertility of any hybrid offspring.
Measure | Species 1 | Species 2 | hybrids |
|---|---|---|---|
Dominant call frequency / kHz | 2.1 | 3.8 | — |
Call pattern | 4 short pulses | 7 long pulses | — |
Mating attempts with conspecifics / 20 trials | 18 | 19 | — |
Mating attempts with the other species / 20 trials | 2 | 1 | — |
Fertile offspring after hybrid crosses / 14 offspring | — | — | 0 |
Identify the prezygotic barrier shown in the data.
[1]
Identify the postzygotic barrier shown in the data.
[1]
Explain how these barriers help prevent mixing of alleles between the two species.
[2]
Question 36
Cytochrome c is a protein found in many eukaryotes. Researchers compared the amino acid sequence of cytochrome c in five vertebrates and used the number of sequence differences to infer evolutionary relationships.
Species | Human | Chimpanzee | Gorilla | Mouse | Chicken |
|---|---|---|---|---|---|
Human | — | 0 | 1 | 7 | 10 |
Chimpanzee | 0 | — | 1 | 7 | 10 |
Gorilla | 1 | 1 | — | 8 | 11 |
Mouse | 7 | 7 | 8 | — | 13 |
Chicken | 10 | 10 | 11 | 13 | — |
I.
Outline why sequence differences in the same protein can be used as evidence for evolution.
[2]
II.
Suggest one limitation of using only cytochrome c sequence data to construct a cladogram.
[1]
Explain how the data could be used to infer which two species are most closely related.
[2]
Evaluate the use of molecular sequence data as evidence for common ancestry compared with evidence from external appearance.
[2]
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Question 37
A population of lizards lives on a small island. During a dry decade, adult lizards develop thicker skin and reduce their daytime activity. Over the same period, young lizards with inherited alleles for lower water loss survive and reproduce more often.
I.
Distinguish between an acquired characteristic and a heritable characteristic using the lizard example.
[2]
II.
State why the inherited change in water loss can be regarded as evolution if it becomes more common in the population.
[1]
Explain why the individual lizards that reduced daytime activity have not evolved by doing so.
[1]
Discuss why evolution by natural selection is described as a scientific theory rather than a formally proven fact.
[2]
Question 38
Wild mustard has been selectively bred by humans to produce crop varieties with enlarged leaves, stems, flower buds or storage organs. These varieties remain closely related but look very different.
I.
Outline the process of selective breeding in crop plants.
[1]
II.
State why variation within the original plant population is necessary for selective breeding.
[1]
Explain how selective breeding of mustard provides evidence that evolutionary change can occur rapidly.
[2]
Discuss one similarity and one difference between selective breeding and natural selection.
[2]
Question 39
Several species of smartweed in the genus Persicaria are thought to have originated by hybridization followed by polyploidy. The table summarizes chromosome sets and fertility in crosses involving two parental species and a derived smartweed species.
Cross or lineage | Chromosome sets in offspring | Fertility |
|---|---|---|
Parent species 1 × Parent species 1 | AA | high fertility |
Parent species 2 × Parent species 2 | BB | high fertility |
Parent species 1 × Parent species 2 | AB | low fertility |
Derived smartweed species | AABB | high fertility |
Derived smartweed × Parent species 1 | AAB | low fertility |
Derived smartweed × Parent species 2 | ABB | low fertility |
Identify the type of polyploidy most consistent with the origin of the derived smartweed species.
[1]
Explain why the initial hybrid is expected to have low fertility.
[2]
Explain how chromosome doubling can cause abrupt speciation in this case.
[2]
Question 40
The figure shows the forelimb skeletons of four vertebrates and the wing of an insect.
I.
Outline why the vertebrate forelimbs are described as homologous structures.
[2]
II.
Identify one bone or bone group that supports the homology of the vertebrate limbs.
[1]
Explain why an insect wing and a bat wing are analogous rather than homologous as wings.
[2]
Compare the evolutionary processes indicated by homologous vertebrate limbs and analogous wings.
[2]
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Question 41
Bonobos and common chimpanzees are closely related species in the genus Pan. Their present ranges are separated by the Congo River.
I.
Identify the type of reproductive isolation shown by the separation of the two populations.
[1]
II.
Outline how geographical isolation affects gene flow between the populations.
[2]
Explain how differential selection could have contributed to divergence after the ancestral population was split by the river.
[3]
Explain why gradual evolutionary change in a single interbreeding lineage is not by itself speciation.
[2]
Question 42
Two alternative diagrams are proposed to summarize the history of a group of island beetles. Diagram X shows one species slowly changing into another in a straight line. Diagram Y shows an ancestral species splitting into several branches, with two branches ending before the present.
I.
State which diagram better represents speciation.
[1]
II.
Justify your answer to part (a)(i).
[2]
Explain the difference between speciation and extinction in the context of the branching diagram.
[2]
Evaluate the statement: "A species that changes gradually over time has necessarily undergone speciation."
[2]
Question 43
Two populations of a frog species are diverging. In case A, populations live on opposite sides of a newly formed mountain range. In case B, populations live in the same wetland, but one group breeds in early spring and the other in late summer.
I.
Identify the type of speciation most likely in case A and in case B.
[2]
II.
Identify the form of reproductive isolation in case B.
[1]
Compare allopatric and sympatric speciation.
[2]
Explain why sympatric speciation can be more difficult to demonstrate than allopatric speciation.
[2]
Question 44
A volcanic island was colonized by a small population of seed-eating birds. Thousands of years later, several closely related bird species occur on the island, each using different food resources.
Bird group | Beak form | Main food | Feeding site |
|---|---|---|---|
Colonizing ancestor | medium, conical | seeds | ground |
Species A | deep, thick, conical | large hard seeds | ground |
Species B | small, narrow, conical | small seeds | grass heads |
Species C | long, slender | insects | bark |
Species D | long, curved | nectar and fruit | flowers |
Species E | short, strong | buds and nuts | shrubs |
I.
Define adaptive radiation.
[1]
II.
Suggest why a newly formed volcanic island can favour adaptive radiation.
[2]
Explain how adaptation to different food resources could allow closely related bird species to coexist.
[2]
Discuss how adaptive radiation can increase biodiversity at more than one level.
[3]
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Question 45
Two closely related grasshopper species live in the same meadow. Males of each species produce a species-specific courtship song. Rare hybrids have been recorded, but laboratory crosses show that hybrid males do not produce functional sperm.
I.
Identify one prezygotic barrier and one postzygotic barrier described in the grasshoppers.
[2]
II.
State why hybrid sterility reduces gene flow between the two species.
[1]
Explain how courtship behaviour can prevent hybridization in animal species.
[2]
Evaluate the importance of both prezygotic and postzygotic barriers in maintaining species boundaries.
[2]
Question 46
Horses and donkeys can mate to produce mules. Most mules are healthy but sterile. Horses and donkeys remain distinct species despite occasional hybridization.
I.
Define an interspecific hybrid.
[1]
II.
Identify the reproductive barrier shown by mule sterility.
[1]
Explain why sterility can occur in hybrids produced from different species.
[2]
Discuss how hybrid sterility helps maintain biodiversity.
[2]
Question 47
Several knotweed and smartweed species in the genus Persicaria are thought to have originated by hybridization followed by polyploidy.
I.
Define polyploidy.
[1]
II.
Distinguish between autopolyploidy and allopolyploidy.
[2]
Explain how hybridization followed by chromosome doubling can restore fertility in an allopolyploid plant.
[3]
Explain why this process can cause abrupt speciation in plants.
[2]
Question 48
Two closely related cichlid fish forms live in the same lake. They occupy overlapping habitats but choose mates using different body colours. Genetic data show reduced interbreeding between the colour forms.
Colour form | Depth range / m | Same-colour mates / n (of 50) | Other-colour mates / n (of 50) |
|---|---|---|---|
Red form | 3-9 | 47 | 3 |
Blue form | 6-12 | 46 | 4 |
I.
Identify the form of reproductive isolation suggested by mate choice based on body colour.
[1]
II.
Explain why the case could be interpreted as sympatric speciation.
[2]
Explain how reduced interbreeding can lead to divergence of the two gene pools.
[2]
Evaluate one alternative explanation that should be considered before concluding that sympatric speciation occurred in this lake.
[2]
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