A4.1 Evolution and speciation
Practice exam-style IB Biology questions for Evolution and speciation, aligned with the syllabus and grouped by topic.
Question 1
A population of lizards develops darker skin after basking in strong sunlight, but their offspring raised in shade are not darker. What conclusion is supported?
A.
The darker skin is an acquired characteristic and is not evidence of evolution.
B.
The darker skin is speciation because a new lizard species has appeared.
C.
The darker skin is evolution because individuals changed in response to the environment.
D.
The darker skin is Lamarckian inheritance because offspring inherit it in shade.
Question 2
Two mammal species have very similar amino acid sequences in the same enzyme. What is the most direct evolutionary inference?
A.
They probably share a relatively recent common ancestor.
B.
They must occupy identical ecological niches.
C.
They are unable to interbreed with other mammals.
D.
They acquired the enzyme by learning the same behaviour.
Question 3
Selective breeding of crop plants is evidence for evolution because it shows that
A.
heritable traits in a population can change markedly over generations.
B.
individual plants can decide to develop useful characteristics.
C.
all crop varieties become separate species after one generation.
D.
wild species have no genetic variation before domestication.
Question 4
The humerus, radius, ulna, carpals, metacarpals and phalanges occur in the same relative positions in a bat wing and a whale flipper. What does this provide evidence for?
A.
Hybrid sterility between mammals
B.
Homology due to common ancestry
C.
Acquired traits caused by swimming
D.
Analogy due to identical function
Question 5
What must occur for speciation, rather than only gradual evolutionary change within one species?
A.
Extinction removes one population from an ecosystem.
B.
All individuals in a population become larger over time.
C.
An individual changes during its lifetime.
D.
A pre-existing species splits into two or more separate species.
Question 6
Two populations become separate species while living in the same lake because females respond to different male courtship colours. What type of speciation is described?
A.
Allopatric speciation involving geographical isolation
B.
Autopolyploid speciation involving chromosome doubling
C.
Adaptive radiation involving temporal isolation only
D.
Sympatric speciation involving behavioural isolation
Question 7
Adaptive radiation most directly increases biodiversity when related species
A.
diversify from a common ancestor into different ecological niches.
B.
all adapt to use the same resource in the same way.
C.
merge their gene pools through fertile hybrids.
D.
lose all inherited variation by selective breeding.
Question 8
Define evolution.
[1]
Distinguish evolution from an acquired characteristic using one example.
[1]
Question 9
State what happens to the total number of species when speciation occurs.
[1]
Outline why gradual change in a single interbreeding lineage is not necessarily speciation.
[1]
Question 10
Bird wings and insect wings are both used for flight but have different evolutionary origins. What process best explains this similarity?
A.
Divergent evolution producing homologous structures
B.
Polyploidy producing new plant species
C.
Convergent evolution producing analogous structures
D.
Extinction reducing total species number
Question 11
An ancestral population of apes is divided by a deep river. Food resources and competitors differ on the two sides. What combination most directly promotes speciation?
A.
Extinction and identical gene pools
B.
High gene flow and identical selection
C.
Acquired behaviours and no heritable variation
D.
Reduced gene flow and differential selection
Question 12
Two closely related plant populations in the same meadow release pollen at different times of year, preventing fertilization between them. What isolation mechanism is shown?
A.
Temporal isolation
B.
Hybrid sterility
C.
Geographic isolation
D.
Adaptive radiation
Question 13
Male frogs of two species call at the same pond, but females mate only with males producing their species-specific call. What type of reproductive barrier is this?
A.
A prezygotic behavioural barrier
B.
A polyploid chromosome barrier
C.
A geographical barrier
D.
A postzygotic sterility barrier
Question 14
A mule is usually sterile because horse and donkey chromosomes do not pair correctly during meiosis. What is the evolutionary effect of this sterility?
A.
It is a prezygotic barrier preventing fertilization.
B.
It prevents most allele flow from hybrids into later generations.
C.
It increases gene flow between horses and donkeys.
D.
It proves that horses and donkeys have identical gene pools.
Question 15
A plant has four complete sets of chromosomes derived from one ancestral species after whole-genome duplication. What is this plant?
A.
An analogous structure
B.
An autopolyploid
C.
A sterile interspecific hybrid only
D.
An allopolyploid
Question 16
State one type of molecular sequence used as evidence for evolution.
[1]
Explain why fewer differences in the same gene sequence between two species support a closer evolutionary relationship.
[1]
Question 17
A farmer breeds only wheat plants with the largest grains for several generations.
State the type of selection involved.
[1]
Outline how this provides evidence that evolution can occur rapidly.
[1]
Question 18
The forelimbs of humans, bats and whales contain the same major bones in the same relative positions.
Name this type of structure.
[1]
Describe how this is evidence for evolution.
[1]
Question 19
Define analogous structures.
[1]
Distinguish analogous structures from homologous structures.
[1]
Give one example of analogous structures.
[1]
Question 20
Define allopatric speciation.
[1]
Define sympatric speciation.
[1]
Compare the requirements for allopatric and sympatric speciation.
[1]
Question 21
State one example of behavioural isolation.
[1]
Distinguish behavioural isolation from temporal isolation.
[1]
Question 22
The table shows the percentage similarity of the cytochrome c amino acid sequence between humans and four other vertebrates.
| Vertebrate species | Similarity to human / % |
|---|---|
| Chimpanzee | 100 |
| Rhesus macaque | 99 |
| Mouse | 91 |
| Chicken | 86 |
Identify the species most closely related to humans according to the table.
[1]
Describe the relationship between sequence similarity and inferred evolutionary relationship.
[1]
Explain why amino acid sequence data can provide evidence for common ancestry.
[1]
Question 23
A population of domesticated hens was selectively bred for high egg production over several generations. The graph shows mean eggs laid per female per year.
State the overall trend shown.
[1]
Estimate the generation in which mean egg production first exceeds the target line shown on the graph.
[1]
Explain how selective breeding could cause the trend.
[1]
Suggest one limitation of using this evidence alone to predict evolution in wild populations.
[1]
Question 24
Evolution by natural selection is described as a scientific theory. What does this mean in biology?
A.
It is a guess that has not been tested experimentally.
B.
It applies only to fossils and not to living populations.
C.
It has been formally proved true by checking all organisms.
D.
It is a broad explanation supported by many observations and successful predictions.
Question 25
Hybridization between two related Persicaria species is followed by chromosome doubling. Why can this cause abrupt speciation?
A.
The new species must occupy the same niche as both parents.
B.
The hybrid immediately loses all chromosomes from both parent species.
C.
The new polyploid may be fertile with similar polyploids but reproductively isolated from parent species.
D.
The parent species become extinct as soon as the hybrid forms.
Question 26
Closely related fish species now live in the same lake. DNA evidence shows they diverged before the lake formed and later colonized it. What conclusion is best supported?
A.
Their present sympatry does not by itself prove sympatric speciation.
B.
They must have speciated sympatrically because they now share a lake.
C.
They cannot be separate species if they live in the same lake.
D.
They must be autopolyploids because DNA differs between them.
Question 27
The Congo River separates bonobos (Pan paniscus) and common chimpanzees (Pan troglodytes).
State the type of reproductive isolation caused by the river.
[1]
Explain how this separation could have contributed to speciation.
[1]
Question 28
State why evolution by natural selection is called a theory.
[1]
Outline why evolution by natural selection is regarded as a pragmatic truth in biology.
[1]
Question 29
Galápagos finches include closely related species with different beak shapes and diets.
Name the evolutionary pattern represented.
[1]
Explain how this pattern can increase biodiversity.
[1]
Question 30
State one prezygotic barrier that can prevent hybridization in animals.
[1]
Explain how this barrier helps maintain species boundaries.
[1]
Question 31
A horse and a donkey can produce a mule, but mules are usually sterile.
Identify whether mule sterility is a prezygotic or postzygotic barrier.
[1]
Explain why mule sterility prevents mixing of alleles between horses and donkeys.
[1]
Question 32
Define polyploidy.
[1]
Distinguish autopolyploidy from allopolyploidy.
[1]
Question 33
The diagram compares the forelimb bones of four vertebrates.
Identify one bone that is present in all four limbs.
[1]
State the term used for structures with this pattern of similarity.
[1]
Explain how the diagram supports common ancestry despite different limb functions.
[1]
Question 34
Two populations of a river fish became separated when a waterfall formed. The graph shows allele frequency at one locus in the upstream and downstream populations over time.
Compare the allele frequencies in the two populations at the start of the study.
[1]
Describe how the allele frequencies change after separation.
[1]
Explain how reproductive isolation and differential selection could lead to speciation in this example.
[1]
Question 35
The figure shows three populations of crickets. Populations X and Y are separated by a mountain range. Populations Y and Z live in the same valley, but males sing at different times of night.
Identify the isolation mechanism between X and Y.
[1]
Identify the isolation mechanism between Y and Z.
[1]
Compare how allopatric and sympatric speciation could occur in these crickets.
[1]
Question 36
The graph shows beak depth and main food source for several related finch species on an island group.
Identify the species most adapted for feeding on large hard seeds.
[1]
Describe the relationship between beak depth and main food source.
[1]
Explain how the pattern shown is evidence of adaptive radiation.
[1]
Question 37
In knotweeds and smartweeds (Persicaria), new species can form after hybridization followed by chromosome doubling.
Name this form of polyploid speciation.
[1]
Explain why chromosome doubling can restore fertility in the hybrid.
[1]
Question 38
Two sister species occur on the same island. Researchers suggest they formed by sympatric speciation.
State one observation that would support sympatric rather than allopatric speciation.
[1]
Explain why the current presence of both species on the island is not sufficient evidence.
[1]
Question 39
The table compares wings of three animal groups.
| Animal group | Main function | Structural origin | Bones present | Developmental origin | Major support tissue |
|---|---|---|---|---|---|
| Bird | Powered flight | Modified forelimb | Yes | Vertebrate limb bud | Bone and feathers |
| Bat | Powered flight | Modified forelimb | Yes | Vertebrate limb bud | Bone and skin membrane |
| Insect | Powered flight | Body wall outgrowth | No | Insect wing pad | Chitin cuticle |
Identify the pair of wings that are most likely analogous.
[1]
Give one item of evidence from the table supporting your answer to (a).
[1]
Explain how convergent evolution could produce the similarity.
[1]
Suggest one additional type of evidence that would help distinguish analogy from homology.
[1]
Question 40
Researchers measured female response to male courtship songs in two closely related grasshopper species. The bar chart shows the percentage of females that approached different song types.
Identify the song type producing the highest response in females of species A.
[1]
Compare the responses of species A and species B females to hybrid songs.
[1]
Explain how courtship behaviour can act as a barrier to hybridization.
[1]
Suggest why a weak response to hybrid songs could maintain separate gene pools.
[1]
Question 41
The table shows chromosome numbers and fertility of crosses among two diploid Persicaria species, their hybrid, and a chromosome-doubled derivative.
| Individual | Chromosome set origin | Total chromosomes / 2n | Pollen fertility / % | Crosses with parents / seeds flower^-1 | Crosses within same type / seeds flower^-1 |
|---|---|---|---|---|---|
| P. species A | AA | 22 | 94 | 31 | 34 |
| P. species B | BB | 20 | 91 | 28 | 30 |
| F1 hybrid | AB | 21 | 3 | 0.4 | 0.2 |
| Doubled derivative | AABB | 42 | 82 | 1.1 | 26 |
Identify the individual most likely to be an allopolyploid.
[1]
State the evidence from the table that the initial hybrid is reproductively isolated.
[1]
Explain why chromosome doubling can increase fertility.
[1]
Suggest why the chromosome-doubled derivative may be considered a new species.
[1]
Question 42
Outline the difference between Darwinian evolution and Lamarckism.
[1]
Discuss why evolution by natural selection is regarded as a scientific theory with strong evidential support.
[1]
Question 43
Describe the pentadactyl limb as an example of a homologous structure.
[1]
Compare and contrast homologous and analogous structures as evidence for evolution.
[1]
Question 44
Outline how selective breeding demonstrates evolutionary change.
[1]
Evaluate the use of molecular sequence data and selective breeding as evidence for evolution.
[1]
Question 45
A phylogeny and distribution map are shown for four related snail species. Species 1 and 2 live on the same coast today. The phylogeny estimates divergence times, and the map shows historical coastlines and barriers.
| Node | Daughter lineages | Split time / Ma | Present-day range | Coastal setting at split | |
|---|---|---|---|---|---|
| A | Species 1 \ | Species 2 | 0.52 | Both on east coast; 45 km overlap | Sand barrier divided north and south coves |
| B | Species 3 \ | Species 4 | 1.10 | Species 3 west island; Species 4 south cape | Deep channel separated island and cape |
| C | Node A \ | Node B | 2.40 | All within same coastal region | Low sea level exposed discontinuous rocky shore |
Identify whether species 1 and 2 are sister species.
[1]
State one item of evidence suggesting they may have diverged allopatrically.
[1]
Explain why present-day sympatry is not enough to infer sympatric speciation.
[1]
Suggest one additional data type that would strengthen the conclusion about mode of speciation.
[1]
Question 46
Outline speciation by splitting of a pre-existing species.
[1]
Explain the roles of reproductive isolation and differential selection in speciation, using the Congo River example.
[1]
Question 47
Distinguish geographic, behavioural and temporal isolation.
[1]
Compare and contrast allopatric and sympatric speciation.
[1]
Question 48
Define adaptive radiation and ecological niche.
[1]
Explain how adaptive radiation can increase biodiversity and allow coexistence of related species.
[1]
Question 49
Distinguish prezygotic and postzygotic reproductive barriers.
[1]
Discuss how barriers to hybridization and hybrid sterility prevent mixing of alleles between species.
[1]
Question 50
Distinguish autopolyploidy from allopolyploidy.
[1]
Explain how hybridization and polyploidy can cause abrupt speciation in plants, using Persicaria as an example.
[1]
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