Question 1
What is a gene pool?
A.
All the species living in the same habitat and able to interact
B.
All the genes and alleles present in an interbreeding population
C.
All the proteins produced by a species in response to its environment
D.
All the phenotypes expressed by one organism during its lifetime
Question 2
The sequence that best summarizes natural selection as a mechanism for evolutionary change is:
A.
environmental need acquired improvement during life direct inheritance of the acquired improvement
B.
identical offspring produced equal competition for resources no change in the next generation
C.
random survival of individuals unchanged reproductive success stable allele combinations in all offspring
D.
variation among individuals differential survival and reproduction change in heritable characteristics of a population
Question 3
What is the difference between the roles of mutation and sexual reproduction in natural selection?
A.
Mutation creates new alleles, while sexual reproduction creates new combinations of alleles.
B.
Mutation always improves fitness, while sexual reproduction always decreases variation between offspring.
C.
Mutation creates new phenotypes only in body cells, while sexual reproduction creates new alleles in gametes.
D.
Mutation changes allele combinations without changing DNA, while sexual reproduction changes the base sequence of genes.
Question 4
A population of shore plants releases thousands of seeds each year, but only a small proportion grow into reproductive adults. What factor most directly promotes natural selection in this situation?
A.
Inheritance of acquired height caused by exposure to sunlight
B.
Equal survival of all seedlings in the same habitat
C.
Competition among seedlings for light, water and mineral ions
D.
Absence of variation in root length among the seedlings
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Question 5
A population of beetles reproduces sexually. A new allele affecting body colour first appeared in one beetle.
State how a new allele can arise.
[1]
Outline how sexual reproduction increases the variation on which natural selection acts.
[2]
Question 6
A population of wild mice lives in an isolated valley. Individuals in the population carry different alleles for coat colour.
Define gene pool.
[1]
Explain why evolution is described as a change in a population rather than in an individual mouse.
[2]
Question 7
A severe frost kills most young plants of a species across a large valley, whether they grow close together or far apart. What type of selection pressure is described?
A.
A density-independent abiotic factor
B.
Intraspecific competition for a limiting resource
C.
A density-dependent biotic factor
D.
Sexual selection caused by differences in mate choice
Question 8
A population of lizards develops larger leg muscles after repeatedly climbing steep rocks. Their offspring do not show larger leg muscles unless they also climb often. What conclusion follows?
A.
The larger muscles are acquired characteristics and are not causing evolutionary change by natural selection.
B.
The larger muscles are heritable because they increase survival on steep rocks.
C.
The larger muscles are mutations that must increase in frequency in the next generation.
D.
The larger muscles prove that sexual reproduction has produced a new allele.
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Question 9
The image that shows sexual selection acting in an animal population is:
A.
B.
C.
D.
Question 10
A database shows that allele has a high frequency in an island population and a low frequency in a mainland population of the same species. The two populations have been separated by ocean for many generations. What is the most justified conclusion from these data alone?
A.
The mainland population cannot contain allele in its gene pool.
B.
Natural selection is proven to be the only cause of the high island frequency.
C.
Geographical isolation is associated with different allele frequencies in the two populations.
D.
The island and mainland populations must now be different biological species.
Question 11
A beetle population contains two heritable colour phenotypes. Birds eat green beetles more often than brown beetles on dry brown soil. What is the predicted genetic consequence over several generations?
A.
The gene pool of each individual changes during its lifetime.
B.
Colour alleles remain constant because selection acts only on phenotypes.
C.
Alleles associated with brown colour increase in frequency in the gene pool.
D.
Alleles associated with green colour increase because birds select them by eating them.
Question 12
Observed genotype frequencies for a gene in an adult population differ from Hardy-Weinberg predictions. The survival rate of one genotype is much lower than the survival rates of the other genotypes. What Hardy-Weinberg condition is not being met?
A.
Random mating
B.
Very large population size
C.
No natural selection
D.
No mutation
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Question 13
A population of lizards contains individuals that differ in leg length. Longer-legged lizards can run faster on open ground, but shorter-legged lizards move more effectively among dense shrubs.
Define natural selection.
[1]
Explain how natural selection could cause evolutionary change in the lizard population if the habitat becomes more open.
[3]
Question 14
A tree species produces thousands of seeds each year. Only a small proportion of the seedlings survive under the forest canopy.
State what is meant by carrying capacity.
[1]
Explain how overproduction of seeds and competition for resources can promote natural selection in this tree species.
[3]
Question 15
After an unusually severe winter, survival was compared in two varieties of the same perennial plant. One variety has a heritable form of cold tolerance.
State the abiotic selection pressure in this example.
[1]
Explain why the severe winter could lead to natural selection in the plant population.
[2]
Question 16
A mammal develops stronger leg muscles after repeated running. Its offspring do not have stronger leg muscles at birth.
Distinguish between a heritable trait and an acquired characteristic.
[2]
Explain why stronger muscles acquired by training do not by themselves cause evolutionary change.
[1]
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Question 17
The graphs show changes in the distribution of a quantitative phenotype after selection has acted for several generations. In each graph, the dashed curve shows the original population and the solid curve shows the later population.
Identify the pattern of selection shown in graph A.
[1]
Identify the pattern of selection shown in graph B.
[1]
Identify the pattern of selection shown in graph C.
[1]
State one feature common to all three patterns of selection.
[1]
Question 18
A population of peppered moths, Biston betularia, was monitored in a woodland affected by industrial soot pollution. The graph shows the percentage of dark-coloured moths in samples and an index of soot on tree bark over time.
State the change in the percentage of dark-coloured moths over the period shown.
[1]
Explain how the change in soot level could have caused the change in moth colour frequency by natural selection.
[2]
State one condition needed for the change in moth colour frequency to be evolutionary change.
[1]
Question 19
Two phenotypes of the same freshwater fish population differ in tolerance to low temperature. Juvenile fish were exposed to different minimum water temperatures for one night and survival was recorded.
Identify the phenotype with higher survival at the lowest temperature tested.
[1]
Explain why low temperature can act as an abiotic selection pressure in this population.
[2]
State whether the effect of a severe cold night is more likely to be density-dependent or density-independent.
[1]
Question 20
In a population in Hardy-Weinberg equilibrium, a recessive phenotype occurs at a frequency of . What is the predicted frequency of heterozygotes?
A.
B.
C.
D.
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Question 21
The graph that represents disruptive selection after several generations is:
A.
B.
C.
D.
Question 22
In an experiment based on Endler's guppy studies, male guppies were kept for several generations in streams with no predators, weak predators or strong predators. Mean coloured spot area on males was recorded.
Describe the effect of strong predation on male spot area shown by the data.
[1]
Explain how sexual selection and natural selection can have opposing effects on male colouration in guppies.
[3]
Question 23
An allele frequency database reports the frequency of allele A at a human alcohol dehydrogenase locus as 0.72 in one geographically isolated population and 0.08 in another geographically isolated population.
Calculate the difference in allele A frequency between the two populations.
[1]
Suggest two reasons why geographically isolated populations can have different allele frequencies.
[2]
State why the database pattern alone does not prove that natural selection caused the difference.
[1]
Question 24
In an insect population, allele R contributes to resistance to an insecticide. The insecticide is applied repeatedly over many generations.
State the feature of neo-Darwinism illustrated by this example.
[1]
Explain how repeated insecticide application could change the frequency of allele R in the gene pool.
[3]
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Question 25
Humans can affect evolution in different ways. A breeder chooses chickens with high egg production as parents for the next generation. In a hospital, antibiotic use is followed by an increase in the proportion of resistant bacteria.
Distinguish artificial selection from natural selection in these examples.
[2]
Explain why the increase in resistant bacteria is not an example of artificial selection.
[2]
Question 26
Researchers compared two laboratory lines of the same insect species. One line reproduced asexually and the other reproduced sexually. The table shows genetic variation measured after several generations in the same environment.
Line | Different genotypes at generation 0 | Different genotypes after 10 generations | New alleles detected? |
|---|---|---|---|
Asexual line | 1 | 3 | Yes |
Sexual line | 1 | 12 | Yes |
Identify which line showed the greater number of different genotypes.
[1]
State the source of the new alleles detected in both lines.
[1]
Explain why the sexual line may respond more rapidly to a new selection pressure.
[2]
Question 27
A desert annual plant produces many seeds after rainfall. Seed, seedling and adult plant numbers were recorded in plots with different nitrogen availability.
Soil nitrogen level | Seeds / | Seedlings / | Adults / |
|---|---|---|---|
Low | 420 | 60 | 11 |
Medium | 540 | 100 | 32 |
High | 620 | 140 | 38 |
State the evidence that the plant overproduces offspring.
[1]
Describe the effect of increasing nitrogen availability on adult plant number.
[2]
Suggest how nitrogen availability could promote natural selection in this population.
[2]
Question 28
A grass species grows taller in shaded habitats than in open habitats. Seeds were collected from tall shaded plants and shorter open-habitat plants, then all offspring were grown in identical light and nutrient conditions.
Parent group | Offspring 1 / cm | Offspring 2 / cm | Offspring 3 / cm | Offspring 4 / cm | Offspring 5 / cm |
|---|---|---|---|---|---|
Shaded-habitat parents | 23.8 | 24.0 | 24.1 | 24.3 | 24.3 |
Open-habitat parents | 23.4 | 23.5 | 23.7 | 23.8 | 24.1 |
Compare the mean offspring heights from the two parent groups in the common garden.
[1]
Explain why the taller height of shaded parent plants is unlikely to cause evolutionary change in this case.
[2]
State one additional measurement that would help test whether height has a heritable component.
[1]
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Question 29
A database was searched for a single nucleotide variant in a human alcohol dehydrogenase gene. The table shows allele counts for allele A and allele G in three geographically separated populations.
Population | Allele A copies | Allele G copies |
|---|---|---|
Population 1 | 156 | 84 |
Population 2 | 84 | 116 |
Population 3 | 36 | 164 |
Calculate the frequency of allele A in Population 1.
[2]
Compare the allele A frequencies in the three populations.
[1]
Suggest why these database data alone do not prove that natural selection caused the differences.
[1]
Question 30
A snail population has shell banding scores from 0 to 6. A bird predator preferentially detects snails with intermediate banding on mixed-colour rocks. The frequency distribution of shell banding was measured before and after several generations of predation.
Identify the pattern of selection shown by the change in distribution.
[1]
Distinguish this pattern from stabilizing selection.
[2]
State the effect that all three patterns of selection can have on the gene pool.
[1]
Question 31
A breeder developed a new wheat variety by choosing plants with the heaviest grain to be parents each generation. Grain mass and the frequency of allele H, associated with heavier grain, were recorded.
Generation | Mean grain mass / mg | Allele H frequency |
|---|---|---|
0 | 38.4 | 0.28 |
1 | 41.2 | 0.35 |
2 | 45.0 | 0.44 |
3 | 49.8 | 0.54 |
4 | 55.3 | 0.65 |
5 | 60.1 | 0.74 |
State the change in allele H frequency over the breeding programme.
[1]
Explain why this is artificial selection rather than natural selection.
[2]
Distinguish this process from the evolution of antibiotic resistance when an antibiotic is used.
[1]
Question 32
In a large, randomly mating population, a recessive phenotype occurs in 9% of individuals. The two alleles at this locus are A and a. Assume the population fits the Hardy-Weinberg model for this calculation.
Calculate the frequency of allele a.
[1]
Calculate the frequency of allele A.
[1]
Calculate the predicted frequency of heterozygous individuals.
[1]
State what would be indicated if the observed genotype frequencies differed greatly from Hardy-Weinberg predictions.
[1]
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Question 33
An Endler-style experiment was carried out using male guppies, Poecilia reticulata. Predation pressure was controlled in separate streams. Female guppies were present in all streams. Mean male colour spot area was measured across generations.
State the treatment in which mean spot area increased the most.
[1]
Explain the opposing effects of sexual selection and predation on male spot area.
[2]
Evaluate whether the data support the conclusion that predation pressure affects evolution of male colouration.
[2]
Question 34
A drought affected a population of island lizards. A gene with two alleles, B and b, influences jaw depth. Genotype numbers were recorded in breeding adults before the drought and in surviving breeding adults after the drought.
Genotype | Before drought / adults | After drought / adults |
|---|---|---|
BB | 36 | 30 |
Bb | 48 | 30 |
bb | 16 | 0 |
Total | 100 | 60 |
Calculate the frequency of allele B before the drought.
[2]
Calculate the change in frequency of allele B after the drought.
[2]
Explain how the data support neo-Darwinism.
[1]
Question 35
A recessive genetic condition in a large randomly mating mammal population is caused by genotype aa. A survey estimated the frequency of affected individuals in newborns.
Survey group | Count | Frequency |
|---|---|---|
Affected newborns () | 25 | 0.0025 |
Unaffected newborns ( or ) | 9975 | 0.9975 |
Calculate the frequency of allele a.
[2]
Calculate the expected frequency of heterozygous carriers.
[2]
State why the affected phenotype frequency must not be used directly as .
[1]
Question 36
A population of annual coastal plants grows on sand dunes. After several unusually dry summers, researchers measured survival and seed production of plants with low, medium and high leaf wax thickness.
Leaf wax thickness | Mean survival / % | Mean seed output / seeds plant |
|---|---|---|
Low | 18 | 6 |
Medium | 46 | 18 |
High | 78 | 35 |
I.
Identify the abiotic selection pressure acting on the plant population.
[1]
II.
Outline why this selection pressure can be described as density-independent.
[2]
Explain how natural selection could change the frequency of alleles affecting leaf wax thickness over several generations.
[3]
Evaluate whether the data alone are sufficient evidence that the population has evolved by natural selection.
[1]
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Question 37
On an island, a bird species feeds on seeds. After a storm, only large hard seeds remain common for several years. Beak depth varies among birds in the population.
I.
State one source of new alleles in this bird population.
[1]
II.
Explain how sexual reproduction can increase phenotypic variation without usually creating new alleles.
[2]
Explain how the change in seed availability could cause evolutionary change in beak depth.
[3]
Suggest why the same beak depth may not be advantageous if small soft seeds become common again.
[1]
Question 38
A gardener claims that selecting seeds from the tallest plants grown with extra fertilizer will produce a genetically taller variety after one generation.
I.
Distinguish between a heritable trait and an acquired characteristic.
[2]
II.
State why natural selection requires heritable variation.
[1]
Evaluate the gardener's claim using the information provided.
[3]
Suggest one result from the common garden that would support genuine evolutionary change.
[1]
Question 39
A population of limpets lives on a rocky shore. Females release many larvae, but only a small proportion settle on rock surfaces and survive to reproduce. Space for attachment and algal food are limited.
I.
Define carrying capacity.
[1]
II.
Identify two limiting resources for the limpet population described.
[2]
Explain how overproduction of larvae can promote natural selection in the limpet population.
[3]
Distinguish intraspecific competition from interspecific competition in this context.
[1]
Question 40
For a two-allele gene in a fish population, allele frequencies in zygotes were used to predict Hardy-Weinberg genotype frequencies. Genotype frequencies were then measured in adults from the same cohort.
Identify the genotype that is below the Hardy-Weinberg prediction in the adult population.
[1]
Suggest two Hardy-Weinberg conditions that could have been not maintained.
[2]
Explain why lower adult frequency of aa suggests natural selection may be occurring.
[1]
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Question 41
Male satin bowerbirds decorate bowers and perform displays. Females visit several males before mating. Males with more intense displays may also be more visible to predators.
I.
Define sexual selection.
[1]
II.
Outline two traits in male bowerbirds that could act as signals of overall fitness to females.
[2]
Explain how female mate choice could lead to evolution of more elaborate display behaviour.
[2]
Discuss why a trait that reduces survival can nevertheless become common in an animal population.
[2]
Question 42
In a model based on Endler's guppy experiments, male guppies were kept in replicate streams with either no predators, weak predators or strong predators. Mean area of coloured spots on males was measured over several generations.
I.
Identify the controlled selection pressure in this model.
[1]
II.
Describe the expected change in male colouration when strong predators are present.
[2]
Explain why male colouration may increase when predators are absent or weak.
[2]
Evaluate the use of this model as evidence that selection pressure can cause evolutionary change.
[3]
Question 43
Allele frequency data for a single nucleotide polymorphism in the human alcohol dehydrogenase gene family were obtained from an online database for four geographically separated populations.
Population / origin | Sample size () | allele frequency (%) |
|---|---|---|
Yoruba, Nigeria | 96 | 11 |
Han Chinese, China | 102 | 18 |
Finnish, Finland | 89 | 14 |
Quechua, Peru | 84 | 21 |
I.
Define allele frequency.
[1]
II.
State two pieces of information that should be checked when using an allele frequency database.
[2]
Explain how geographical isolation can lead to different allele frequencies in populations of the same species.
[2]
Discuss why the database pattern alone should not be used to conclude that natural selection caused the differences.
[2]
Question 44
In a beetle population, body colour is influenced by alleles at one gene. Dark beetles are less visible on burnt tree bark than pale beetles. The frequency of the dark-colour allele was estimated before and after a wildfire.
I.
Define gene pool.
[1]
II.
Outline why an individual beetle does not evolve during its lifetime.
[2]
Explain the increase in frequency of the dark-colour allele using neo-Darwinism.
[3]
Suggest one reason why the dark-colour allele might decrease again if unburnt pale bark becomes common.
[1]
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Question 45
Three populations of a small mammal experience different selection pressures affecting adult body mass. Frequency distributions of body mass are shown before and after selection.
Distribution | 8-<10 / g | 10-<12 / g | 12-<14 / g | 14-<16 / g | 16-<18 / g | 18-<20 / g | 20-<22 / g |
|---|---|---|---|---|---|---|---|
A before | 5 | 10 | 20 | 30 | 20 | 10 | 5 |
A after | 0 | 2 | 8 | 15 | 20 | 25 | 30 |
B before | 5 | 10 | 20 | 30 | 20 | 10 | 5 |
B after | 3 | 7 | 17 | 46 | 17 | 7 | 3 |
C before | 5 | 10 | 20 | 30 | 20 | 10 | 5 |
C after | 24 | 16 | 8 | 4 | 8 | 16 | 24 |
I.
Identify which population shows directional selection and justify your choice.
[1]
II.
Identify which population shows stabilizing selection and justify your choice.
[1]
III.
Identify which population shows disruptive selection and justify your choice.
[1]
Compare and contrast the effects of directional, stabilizing and disruptive selection on phenotype distributions.
[3]
Explain why all three patterns can result in a change in allele frequency.
[2]
Question 46
Humans can influence evolution in several ways. A breeder chooses the highest-yielding wheat plants as parents each year. In a separate case, repeated use of an insecticide on stored grain is followed by an increase in resistant beetles.
I.
Define artificial selection.
[1]
II.
Explain why the wheat example is artificial selection.
[2]
Explain why the increase in insecticide-resistant beetles is natural selection rather than artificial selection.
[2]
Discuss one possible unintended consequence of strong artificial selection in crop plants.
[2]
Question 47
A recessive inherited condition in an isolated population is caused by allele . In a sample of newborns, 9 in 10000 show the recessive phenotype. Assume Hardy-Weinberg equilibrium for the initial calculation.
I.
Calculate the frequency of allele .
[2]
II.
Calculate the expected frequency of heterozygous carriers.
[2]
State two conditions that must be maintained for Hardy-Weinberg equilibrium in this population.
[2]
Evaluate what it would mean if the observed heterozygote frequency in adults was much lower than the value calculated for newborns.
[2]
Question 48
Two geographically isolated lake populations of the same fish species were genotyped for a two-allele gene associated with low-oxygen tolerance. Observed genotype frequencies were compared with Hardy-Weinberg predictions.
Genotype | Lake A observed / % | Lake A expected / % | Lake B observed / % | Lake B expected / % |
|---|---|---|---|---|
AA | 35 | 36 | 62 | 49 |
Aa | 49 | 48 | 28 | 42 |
aa | 16 | 16 | 10 | 9 |
I.
State the Hardy-Weinberg equation for a gene with two alleles.
[1]
II.
Outline what is meant by genetic equilibrium.
[2]
Explain why one lake population might not fit Hardy-Weinberg predictions.
[3]
Evaluate whether a poor fit to Hardy-Weinberg predictions proves that natural selection is occurring in the lake population.
[2]
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