Question 1
Leaf lengths in a sample from one tree range smoothly from short to long, with many intermediate values. What type of variation is shown?
A.
Continuous variation
B.
Speciation variation
C.
Binomial variation
D.
Discontinuous variation
Question 2
The scientific name of the snow leopard is Panthera uncia. What does this name show?
A.
Panthera uncia is a common name.
B.
Panthera is the family name.
C.
Panthera is the genus name.
D.
uncia is the genus name.
Question 3
A field guide groups several beetles as one species because they have the same body shape, wing-case pattern and antenna structure. What species concept is being used?
A.
Morphological species concept
B.
Asexual species concept
C.
Genomic species concept
D.
Biological species concept
Question 4
A student is arranging stained chromosomes into homologous pairs to make a karyogram. What evidence should be used to match chromosomes?
A.
Cell type, tissue mass and chromosome staining time
B.
Gene expression, cytoplasm colour and cell membrane shape
C.
Nuclear size, organelle number and chromosome movement
D.
Banding pattern, chromosome length and centromere position
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Question 5
Researchers compare whole genome sequences from several finch species to infer how recently they shared common ancestors. What current use of whole genome sequencing is shown?
A.
Counting chromosomes during metaphase
B.
Producing fertile hybrids between species
C.
Naming species by morphology
D.
Researching evolutionary relationships
Question 6
A unicellular eukaryote reproduces asexually by mitosis and has no observed fusion of gametes. Why is the biological species concept difficult to apply to this organism?
A.
Asexual organisms cannot be grouped by any traits.
B.
There is no interbreeding test based on fertile offspring.
C.
There is no DNA present for comparison between cells.
D.
Asexual organisms never have variation in their genomes.
Question 7
An antibiotic resistance gene is found in two distantly related bacterial lineages. DNA sequence evidence shows that the gene moved between cells rather than being inherited from a parent cell. What process explains this pattern?
A.
Vertical gene transfer
B.
Binomial nomenclature
C.
Horizontal gene transfer
D.
Chromosome pairing
Question 8
What is the role of a DNA barcode when environmental DNA is used to investigate biodiversity in a pond?
A.
It is the complete genome sequence of every organism in the pond.
B.
It is a chromosome image arranged from largest to smallest.
C.
It is a visible body feature used to separate organisms in a dichotomous key.
D.
It is a short standard DNA sequence compared with a reference database to identify species.
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Question 9
Students measured the lengths of leaves from one oak tree and also recorded flower colour in a patch of pea plants.
State one reason why variation between organisms is considered a defining feature of life.
[1]
Distinguish between continuous and discontinuous variation using the observations in the stem.
[2]
Question 10
The scientific name of the lion is Panthera leo. The tiger is named Panthera tigris.
Identify the genus name in Panthera leo.
[1]
Outline two conventions used when writing a binomial name.
[2]
Question 11
Two populations of the same lizard species become separated by a mountain range. Over many generations they become increasingly different in colour and body size, but there is no opportunity to test whether they can interbreed. What conclusion is most consistent with speciation occurring gradually?
A.
They must be the same species until they look identical.
B.
They must be different species as soon as one trait differs.
C.
They cannot become different species unless chromosome number changes.
D.
Classifying them as populations or species may be partly arbitrary.
Question 12
A horse has 64 chromosomes in diploid cells and a donkey has 62. Their hybrid offspring, a mule, usually has 63 chromosomes and is infertile. What is the best explanation for the infertility?
A.
The chromosomes cannot all pair correctly during meiosis.
B.
The mule has no genes on its chromosomes.
C.
The mule cannot produce body cells by mitosis.
D.
The chromosomes are too small to carry DNA.
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Question 13
A student is making a dichotomous key for four local plant species. One pair of alternatives is “plant is attractive” and “plant is unattractive”. What change would most improve this step?
A.
Add more species from habitats that were not sampled.
B.
Make both alternatives refer to different features of the plant.
C.
Use only the Latin names and remove all trait descriptions.
D.
Replace it with two clear alternatives using the same visible feature.
Question 14
Two populations of butterflies have different wing patterns. In captivity, individuals from the two populations sometimes mate and the offspring are fertile.
State the biological species concept.
[1]
Explain why the observations could lead to different conclusions using the morphological and biological species concepts.
[3]
Question 15
The cost of whole genome sequencing has decreased and the speed of sequencing has increased.
State what is determined by whole genome sequencing.
[1]
Explain one current use and one potential future use of whole genome sequencing.
[3]
Question 16
A strain of Escherichia coli that was previously susceptible to an antibiotic is later found to carry a plasmid with an antibiotic resistance gene.
State the term for movement of a gene into a bacterial cell from another organism that is not its parent.
[1]
Suggest why this observation is evidence against using the biological species concept for bacteria.
[2]
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Question 17
A student measured two traits in a population of wild radish, Raphanus raphanistrum, growing on the edge of a field.
Plant no. | Leaf length / cm | Flower colour |
|---|---|---|
1 | 6.1 | white |
2 | 9.4 | yellow |
3 | 7.3 | purple |
4 | 8.8 | white |
5 | 5.9 | yellow |
6 | 10.1 | white |
7 | 7.7 | purple |
8 | 6.5 | white |
9 | 11.2 | yellow |
10 | 8.0 | purple |
11 | 7.0 | white |
12 | 9.0 | yellow |
13 | 6.8 | purple |
14 | 10.4 | white |
15 | 5.4 | yellow |
Identify the trait that shows continuous variation.
[1]
Describe the evidence from the data that flower colour shows discontinuous variation.
[1]
Explain how patterned variation allows organisms to be named and classified.
[2]
Question 18
Four specimens of a freshwater snail were collected from nearby streams. A taxonomist compared their shell morphology.
Specimen | Shell height / mm | Shell width / mm | Number of whorls | Aperture shape | Spire height | Shell surface |
|---|---|---|---|---|---|---|
A | 19 | 8 | 5 | oval | high | smooth |
B | 20 | 8 | 5 | oval | high | smooth |
C | 18 | 9 | 5 | oval | high | smooth |
D | 13 | 14 | 3 | round | low | ridged |
State the species concept being used when specimens are grouped mainly by body form and structure.
[1]
Using the data, suggest which specimen is least likely to belong to the same species as the other three.
[1]
Suggest one limitation of using only shell morphology to decide whether the snails belong to one species or more than one species.
[2]
Question 19
A museum database lists scientific names and selected traits for several closely related orchids.
Record | Scientific name | Growth habit | Flower colour | Native region |
|---|---|---|---|---|
A | Dendrobium nobile | Epiphytic | White and pink | China and India |
B | Phalaenopsis amabilis | Epiphytic | White | Southeast Asia |
C | Cattleya labiata | Epiphytic | Purple | Brazil |
D | Dendrobium moniliforme | Epiphytic | Pale pink | East Asia |
E | Cymbidium goeringii | Terrestrial | Green-yellow | East Asia |
State the part of a binomial name that identifies the genus.
[1]
Identify two records in the database that would be expected to have the most similar traits based on their binomial names.
[1]
Explain why scientific names are preferable to common names in an international database.
[1]
Question 20
A short DNA barcode from a stream water sample closely matches the barcode of a protected fish species in a reference database. The fish was not seen during daytime net surveys. What conclusion is best supported?
A.
The species is likely to have left DNA in the stream, but further sampling is needed.
B.
The database match should be ignored because water cannot contain DNA.
C.
The species is definitely absent because no individuals were captured.
D.
The species is certainly breeding in the stream at a large population size.
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Question 21
A cell sample is used to prepare a karyogram.
State the stage of cell division at which chromosomes are most suitable for karyotyping.
[1]
Explain how chromosomes are matched into homologous pairs in a karyogram.
[3]
Question 22
A student used a genome size database to compare several eukaryotes, including animals, plants, fungi and protists.
Species | Group | Level of organisation | Genome size / Gbp |
|---|---|---|---|
Saccharomyces cerevisiae | fungus | unicellular | 0.012 |
Amoeba dubia | protist | unicellular | 670 |
Arabidopsis thaliana | plant | multicellular | 0.135 |
Drosophila melanogaster | animal | multicellular | 0.18 |
Homo sapiens | animal | multicellular | 3.2 |
State what is meant by genome size.
[1]
Evaluate the claim that more complex eukaryotes always have larger genomes.
[3]
Question 23
Many bacteria reproduce by binary fission and can also acquire genes from unrelated bacterial cells.
State why the biological species concept is difficult to apply to organisms that reproduce only asexually.
[1]
Explain how horizontal gene transfer blurs species boundaries in bacteria.
[3]
Question 24
Two closely related plant species have different diploid chromosome numbers. A rare hybrid seedling forms after cross-pollination.
State why chromosome number is usually a shared trait within a sexually reproducing species.
[1]
Explain why the hybrid seedling is unlikely to produce fertile offspring.
[3]
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Question 25
Water samples from a pond were filtered and the DNA extracted. A short barcode region was amplified and compared with reference sequences in a database.
Source | Barcode sequence (12 bp) | Mismatches to pond sample | Read counts in 3 PCR replicates |
|---|---|---|---|
Pond eDNA sample | ATGCTACGTTAG | 0 | 46, 49, 47 |
Species A | ATGCTACGTTAG | 0 | — |
Species B | ATGCTACGCTAG | 1 | — |
Species C | ATGATACGTTAA | 2 | — |
Species D | TCGCTTCGATCG | 4 | — |
State what is meant by environmental DNA.
[1]
Explain how DNA barcodes can be used to identify a species from the pond sample.
[3]
Question 26
Researchers tested breeding compatibility among three populations of grasshopper, Chorthippus, from different valleys. They recorded whether mating occurred, whether offspring hatched and whether the offspring were fertile.
Population pair | Mating occurred | Offspring hatched | Offspring fertile |
|---|---|---|---|
Valley A Valley B | Yes | Yes | Yes |
Valley A Valley C | Yes | Yes | No |
Valley B Valley C | No | No | No |
State the criterion used by the biological species concept.
[1]
Using the data, identify the pair of populations that provides the strongest evidence for belonging to the same biological species.
[1]
Evaluate whether the biological species concept gives a clear decision for all three populations.
[3]
Question 27
Two populations of island lizard, Anolis, were separated by the formation of a sea channel. Researchers measured trait divergence and successful interbreeding over time.
Describe the relationship between time since separation and trait divergence.
[1]
Explain why it may be arbitrary to decide the exact time at which the two populations became separate species.
[2]
Suggest one process that could cause the two non-interbreeding populations to become increasingly different.
[1]
Question 28
Genome sequences were compared for several bacterial isolates collected from a hospital ward. A gene conferring resistance to an antibiotic was detected in distantly related lineages.
Isolate | Clade | Resistance gene |
|---|---|---|
H1 | I | present |
H2 | I | present |
H3 | II | absent |
H4 | II | absent |
H5 | III | absent |
H6 | III | absent |
H7 | IV | present |
H8 | IV | present |
Identify the pattern in the data that suggests horizontal gene transfer.
[1]
Distinguish horizontal gene transfer from vertical transfer.
[2]
Explain why the biological species concept is difficult to apply to these bacteria.
[1]
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Question 29
Asexual freshwater protists were sampled from ponds across a region. Researchers compared cell morphology and DNA sequence similarity among clonal lineages.
Lineage | Pond site | Cell shape | Cell size / µm | DNA similarity to reference / % |
|---|---|---|---|---|
L1 | North shaded pond | oval | 99.8 | |
L2 | North shaded pond | oval | 99.5 | |
L3 | North shaded pond | oval | 99.2 | |
L4 | East reed pond | spindle | 98.4 | |
L5 | East reed pond | spindle | 98.1 | |
L6 | West bog pool | spherical | 97.3 |
State why the biological species concept cannot be applied directly to these protists.
[1]
Using the data, suggest one alternative type of evidence that could be used to group the lineages.
[1]
Suggest why treating every long-lasting clone as a separate species may be problematic.
[2]
Question 30
Four local tree species were identified from their leaves during a field investigation.
State one feature of a leaf that would be reliable for use in a dichotomous key.
[1]
Construct two paired choices that could be used as one step in a dichotomous key for these leaves.
[2]
Suggest why a key should be tested using actual specimens from the local area.
[1]
Question 31
Conservation biologists used eDNA samples to monitor a rare amphibian in three wetlands over two years.
Wetland | Y1 R1 | Y1 R2 | Y1 R3 | Y2 R1 | Y2 R2 | Y2 R3 |
|---|---|---|---|---|---|---|
W1 | Neg | Neg | Neg | Neg | Pos | Neg |
W2 | Neg | Amb | Neg | Neg | Neg | Neg |
W3 | Neg | Neg | Neg | Neg | Neg | Neg |
Suggest one reason why eDNA sampling may be useful for monitoring a rare amphibian.
[1]
Evaluate how reliable negative eDNA results are as evidence that the amphibian is extinct in a wetland.
[3]
Question 32
The hypothesis that human chromosome 2 arose by fusion of two ancestral primate chromosomes was tested using chromosome banding and DNA sequence evidence.
State one feature used to classify chromosomes in a karyogram.
[1]
Describe one piece of evidence in the stimulus that supports the chromosome fusion hypothesis.
[2]
Explain why this is a testable scientific hypothesis rather than a non-testable statement.
[2]
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Question 33
Two closely related lily species were crossed in a greenhouse. The parent species differ in diploid chromosome number. Fertility of the hybrids was assessed by pollen viability and seed production.
Group | Diploid number () / chromosomes | Chromosome pairs formed at meiosis / pairs | Pollen viability / % | Seeds per capsule / no. |
|---|---|---|---|---|
Parent species 1 | 24 | 12 | 95 | 110 |
Parent species 2 | 26 | 13 | 93 | 104 |
Hybrid | 25 | 5 | 14 | 6 |
State why diploid chromosome numbers in plant and animal body cells are usually even.
[1]
Describe the relationship shown between chromosome pairing in the hybrid and fertility.
[1]
Explain how different chromosome numbers can contribute to reproductive isolation between closely related species.
[3]
Question 34
Students developed a dichotomous key for six common tree species on a school site. They recorded visible leaf traits from several specimens of each species.
Species / step | Arrangement | Simple/compound | Lobed | Margin | Leaf length / cm |
|---|---|---|---|---|---|
Ash | opposite | compound | not lobed | toothed | 18-25 |
Field maple | opposite | simple | lobed | smooth | 6-11 |
Oak | alternate | simple | lobed | smooth | 7-13 |
Sycamore | opposite | simple | lobed | toothed | 8-14 |
Hazel | alternate | simple | not lobed | toothed | 4-9 |
Lime | alternate | simple | not lobed | toothed | 5-12 |
Key 1a | — | — | — | — | large leaves |
Key 1b | — | — | — | — | small leaves |
Identify one trait in the data that is suitable for an early step in a dichotomous key.
[1]
Explain why paired statements in a dichotomous key should describe the same type of feature.
[2]
Evaluate one weakness in the draft key and suggest an improvement.
[2]
Question 35
Water samples from three ponds were analysed for environmental DNA. A short barcode region was amplified and compared with a reference database for amphibians.
Pond sample | Barcode match / % | Sequence reads | Field confirmed? |
|---|---|---|---|
Pond A | 93.8 | 24 | No |
Pond B | 99.1 | 437 | Yes |
Pond C | 95.6 | 11 | No |
State what is meant by environmental DNA.
[1]
Using the data, identify the pond with the strongest evidence for the presence of an amphibian species.
[1]
Suggest two reasons why a barcode result may not prove that the species is currently living in the pond.
[2]
Suggest why a short DNA barcode can distinguish species but still be amplified from many related species.
[1]
Question 36
Two populations of coastal beetle are found on separate islands. Adults from the two islands have different body colour and slightly different antennal length. In captivity, some individuals from the two islands mate and produce fertile offspring.
I.
State one trait that could be used in the morphological species concept for these beetles.
[1]
II.
Outline why the observation of fertile offspring supports the biological species concept.
[2]
Explain why morphology alone might lead to a different conclusion from the biological species concept in this example.
[2]
Discuss whether the two island populations should be classified as one species or two species.
[2]
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Question 37
A student compared information for four primate species in a database. The table shows diploid chromosome number and relative genome size.
Species | Diploid chromosome number / chromosomes | Genome size / Gb |
|---|---|---|
Human | 46 | 3.2 |
Chimpanzee | 48 | 3.3 |
Gorilla | 48 | 3.0 |
Rhesus macaque | 42 | 2.9 |
I.
State the diploid chromosome number in humans and in chimpanzees.
[2]
II.
State why diploid chromosome numbers in plants and animals are usually even.
[1]
Explain why chromosome number is not a reliable measure of organism complexity.
[2]
Evaluate the use of the database table to test the claim that species with more chromosomes have larger genomes.
[2]
Question 38
Whole genome sequencing is increasingly used in research and medicine. The flow diagram summarizes how a genome sequence from an individual or organism can be generated and compared with other genome sequences.
I.
Define whole genome sequencing.
[1]
II.
State one reason why whole genome sequencing is now used more widely than in the past.
[1]
Explain how whole genome sequencing can be used to investigate evolutionary relationships.
[2]
Evaluate the potential use of whole genome sequencing in personalized medicine.
[3]
Question 39
Conservation biologists monitored a rare fish, Phoxinus caeruleus, in a river system using eDNA barcodes over five years. Habitat quality and population estimates from net surveys were also recorded.
Year | Site | eDNA reads / count | Habitat quality /10 | Net survey count / fish |
|---|---|---|---|---|
1 | Site A | 5 | 7 | 8 |
1 | Site B | 2 | 5 | 4 |
1 | Site C | 0 | 2 | 1 |
2 | Site A | 7 | 8 | 10 |
2 | Site B | 1 | 5 | 3 |
2 | Site C | 0 | 2 | 0 |
3 | Site A | 9 | 8 | 12 |
3 | Site B | 2 | 4 | 4 |
3 | Site C | 0 | 1 | 0 |
4 | Site A | 12 | 9 | 14 |
4 | Site B | 1 | 4 | 2 |
4 | Site C | 0 | 1 | 0 |
5 | Site A | 15 | 9 | 16 |
5 | Site B | 0 | 3 | 1 |
5 | Site C | 0 | 1 | 0 |
Describe one trend in the eDNA data that suggests persistence of P. caeruleus at a site.
[1]
Suggest one factor in the dataset that could explain increased persistence of the species at one site.
[1]
Evaluate the use of eDNA alone for deciding whether the species has gone extinct from a site.
[3]
Question 40
The diagram shows a simplified comparison between human chromosome 2 and two chromosomes from a close primate relative. Biologists have proposed that human chromosome 2 arose by fusion of two ancestral chromosomes.
I.
Identify two features used to classify chromosomes in a karyogram.
[2]
II.
State why chromosomes are usually photographed for karyotyping during metaphase.
[1]
Explain how the chromosome evidence in the diagram supports the fusion hypothesis.
[3]
Distinguish between the fusion hypothesis and a non-testable statement about the origin of human chromosome 2.
[2]
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Question 41
A genome size database was searched for several eukaryotes. The graph compares genome size with a simple estimate of organism complexity based on number of cell types.
I.
State what is meant by genome size.
[1]
II.
State one reason for using a logarithmic scale for genome size in this comparison.
[1]
Explain why a large genome does not necessarily mean that an organism has more genes.
[2]
Discuss whether the graph supports the claim that more complex eukaryotes have larger genomes.
[3]
Question 42
A plant species grows across a long mountain range. Populations at neighbouring sites can cross-pollinate, but populations at opposite ends of the range flower at different times and show large differences in leaf shape.
I.
Define population.
[1]
II.
Define speciation.
[1]
Explain why it may be difficult to decide whether the end populations are different species.
[3]
Discuss how this example shows both continuous and discontinuous patterns of variation.
[2]
Question 43
A bacterial pathogen is sampled from three hospitals. Genome comparisons show that most of each genome is similar, but an antibiotic resistance gene has moved into two lineages that are otherwise only distantly related.
I.
Define horizontal gene transfer.
[1]
II.
State why the transferred resistance gene is not an example of vertical transfer.
[1]
Explain why horizontal gene transfer makes the biological species concept difficult to apply to bacteria.
[2]
Evaluate whether whole genome similarity or the resistance gene alone should be used to identify bacterial species in this investigation.
[3]
Question 44
Two closely related grass species have different diploid chromosome numbers. They occasionally cross-pollinate and form vigorous hybrid plants, but the hybrids produce very little viable pollen.
I.
State what is meant by homologous chromosomes.
[1]
II.
State why chromosome number is usually a shared trait within a sexually reproducing species.
[1]
Explain why hybrids between the two grass species may be infertile even if they grow vigorously.
[3]
Discuss whether different chromosome numbers always prevent fertilization between related species.
[2]
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Question 45
Four local tree species were sampled from a school site. The leaves are shown in the diagram and labelled A, B, C and D.
I.
State two features of the leaves that would be reliable for constructing a dichotomous key.
[2]
II.
Explain why vague features such as “large” and “small” should be avoided unless defined.
[1]
Construct a dichotomous key that could be used to identify leaves A, B, C and D.
[3]
Evaluate the reliability of a dichotomous key developed from one sample of each tree species.
[2]
Question 46
A conservation team wants to know whether a threatened freshwater fish still occurs in a river after a pollution event. They plan to combine eDNA barcoding with traditional net sampling.
I.
State one condition that would make a species more likely to persist in the river.
[1]
II.
State one factor that would make extinction from the river more likely.
[1]
Explain why eDNA barcoding and net sampling may give different conclusions about whether the fish is present.
[3]
Evaluate the sampling plan for deciding whether the fish has gone extinct from the river.
[2]
Question 47
Environmental DNA was collected from three ponds to investigate amphibian biodiversity. Barcode sequences from each water sample were compared with a reference database.
Pond | Best barcode match | Sequence identity / % | Matching reads / count |
|---|---|---|---|
1 | Common frog | 99.8 | 184 |
2 | Rare amphibian species | 99.1 | 5 |
3 | Smooth newt | 99.7 | 173 |
I.
Define environmental DNA.
[1]
II.
Outline the role of a DNA barcode in this investigation.
[2]
Explain why eDNA sampling can detect species that are difficult to find by direct observation.
[2]
Evaluate the use of the eDNA results to decide whether the rare amphibian species persists in pond 2.
[3]
Question 48
A lake contains asexually reproducing algae. Several clonal lineages differ by small numbers of mutations and by the habitats they occupy in the lake. Some lineages are almost identical in appearance.
I.
Define asexual reproduction.
[1]
II.
State what is meant by a clone in this context.
[1]
Explain why the biological species concept is difficult to apply to the algae.
[2]
Discuss how biologists could decide whether the clonal lineages should be named as one species or several species.
[3]
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