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Evolution

Evolution — Free MYP5 Biology Practice Questions

1QuestionDevelopment of the Theory of Evolution by Natural SelectionConcept Practice

2 marks~3 minCriterion A

Darwin observed that individuals within a population show heritable variation. Some variants survive and reproduce more successfully than others in a given environment — a process he called natural selection.

Identify one source of heritable variation in a population. [1]

Explain how natural selection acting on heritable variation can lead to a change in the characteristics of a population over many generations. [1]

Solutions

2QuestionDifferential Reproduction and FitnessConcept Practice

2 marks~3 minCriterion A

The diagram shows two bird species on an island. Species A has a large, thick beak and feeds on large, hard seeds. Species B has a small, slender beak and feeds on small, soft seeds. A prolonged drought causes small, soft seeds to become scarce, leaving large, hard seeds as the dominant food source.

Identify which species has a selective advantage in the post-drought environment and explain why. [1]

Explain how this selective advantage leads to differential reproduction, and what effect this has on the fitness of each species in the altered environment. [1]

Solutions

3QuestionBehavioral AdaptationsConcept Practice

2 marks~3 minCriterion A

The photograph shows a large colony of emperor penguins (Aptenodytes forsteri) huddling tightly together on Antarctic sea ice during winter, when air temperatures fall below −40 °C and wind speeds exceed 100 km h⁻¹.

Identify the type of behavioural adaptation shown in the photograph. [1]

Explain how this behaviour increases the survival rate of emperor penguins in Antarctic winter conditions. [1]

Solutions

4QuestionBiogeography and Species DistributionConcept Practice

2 marks~3 minCriterion A

Marsupials — mammals that raise young in a pouch — are found today on several continents, but one continent hosts by far the greatest diversity and concentration of marsupial species.

Identify the continent with the highest concentration of marsupials today. [1]

Using the theory of continental drift, explain one reason why marsupials are so highly concentrated on this continent. [1]

Solutions

5QuestionComparative Anatomy and Homologous StructuresConcept Practice

2 marks~3 minCriterion A

The diagram below shows the forelimb skeletons of a human, a cat, and a whale. Bone

X

is labelled on the human arm.

Identify bone

X

. [1]

Define the term homologous structure, referring to the limbs shown. [1]

Solutions

6QuestionDevelopment of the Theory of Evolution by Natural SelectionAssessment Practice

4 marks~6 minCriterion A

A hospital records a rise in treatment failures caused by Staphylococcus aureus. The diagram shows the bacterial population before and after a course of antibiotics: before exposure, most bacteria are non-resistant (blue) and a few are resistant (red); after exposure, only resistant bacteria remain.

State one source of genetic variation that could produce antibiotic-resistant bacteria within a population before any antibiotic exposure. [1]

Using the diagram, explain how differential survival leads to a change in the composition of the bacterial population during antibiotic exposure. [2]

Analyse how inheritance of the resistance trait, across successive generations, results in a population that is predominantly resistant. [1]

Solutions

7QuestionVoyage of the HMS Beagle and ObservationsAssessment Practice

2 marks~3 minCriterion B

During his voyage on the HMS Beagle, Darwin observed finch species across the Galápagos Islands. The table below summarises his findings.

Species	Beak shape	Primary food source
Ground Finch	blunt	seeds
Tree Finch	pointed	insects
Cactus Finch	curved	cactus nectar
Warbler Finch	thin	small insects
Woodpecker Finch	strong	larvae under bark

Identify the pattern linking beak shape to food source in the data above. [1]

A new finch species is discovered on an island where the only food source is large, hard-shelled nuts. Deduce the most likely beak shape for this species, justifying your answer using evidence from the data. [1]

Solutions

8QuestionVariation within PopulationsAssessment Practice

5 marks~8 minCriterion C

A population of beetles lives on a dark forest floor. Before a predation event, the population contains green, brown, and black individuals. After birds forage in the area, only black beetles remain; green and brown individuals have been consumed.

State what the left panel of the diagram reveals about variation in the beetle population before predation occurs. [1]

Explain how the diagram demonstrates that predation acts as a selective pressure rather than a cause of variation. [2]

Evaluate the assertion that variation within a population is influenced by predation pressure. [2]

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Solutions

9QuestionVariation within PopulationsAssessment Practice

2 marks~3 minCriterion D

In captive breeding programmes for endangered species such as the California condor, conservation biologists use DNA markers to assess genetic variation across individuals. Breeding pairs are selected to maximise genetic diversity and minimise inbreeding depression within the captive population.

Outline how genetic variation data are used in this captive breeding programme to support species conservation. [1]

Describe one ethical issue that arises from humans controlling which individuals reproduce in this programme. [1]

Solutions

10QuestionDevelopment of the Theory of Evolution by Natural SelectionAssessment Practice

5 marks~8 minCriterion C

Three fossil sequences are described below.

Sequence 1 — Fish to tetrapod: Tiktaalik (375 Ma) possesses lobe fins, a flat skull, and a neck; later tetrapod fossils show limbs with digits.

Sequence 2 — Dinosaur to bird: Archaeopteryx (150 Ma) retains a long bony tail and clawed wings alongside feathers; later bird fossils show tail reduction and fused wing bones.

Sequence 3 — Land to sea: Pakicetus (50 Ma) is a terrestrial mammal with ears adapted for underwater hearing; later whale fossils (Ambulocetus, Dorudon) show progressively reduced hind limbs and developed tail flukes.

For one sequence of your choice, identify an anatomical feature that changes over time and explain how this supports Darwin's hypothesis of gradual change through natural selection. [2]

Evaluate whether the three sequences together provide convincing evidence for Darwin's hypothesis, considering both the support offered by the fossil record and the limitations imposed by its incompleteness. [3]

Solutions

11QuestionDevelopment of the Theory of Evolution by Natural SelectionAssessment Practice

7 marks~11 minCriterion A

A culture of E. coli is exposed to increasing antibiotic concentrations over 10 generations. The data below show the conditions and outcomes for each generation.

Generation	1	2	3	4	5	6	7	8	9	10
Antibiotic concentration (mg/L)	0	10	10	20	20	30	30	40	40	50
Surviving bacteria (thousands)	100	85	80	65	55	40	35	25	20	15

Describe the pattern shown in the data, referring to both the number of surviving bacteria and the rate of change across generations. [2]

Explain how natural selection accounts for the pattern observed. In your answer, refer to variation, selection pressure, and heritability. [3]

The antibiotic concentration is increased to 60 mg/L in generation 11. Analyse whether the bacterial population is more or less likely to be eliminated compared with earlier generations, and justify your reasoning using evidence from the data. [2]

Solutions

12QuestionVariation within PopulationsAssessment Practice

4 marks~6 minCriterion D

A patient prescribed a 7-day antibiotic course feels better after 3 days and stops taking the medication. Within the bacterial population, individuals vary genetically; some carry heritable traits conferring resistance to the antibiotic.

Explain how genetic variation within the bacterial population contributes to the survival of resistant bacteria when antibiotics are present. [1]

Explain the direct health consequences for this patient of stopping the antibiotic course early. [1]

Discuss the broader public health implications of incomplete antibiotic treatment and the ethical responsibility of the patient to complete the prescribed course. [2]

Solutions

13QuestionDifferential Reproduction and FitnessAssessment Practice

4 marks~6 minCriterion A

The diagram shows two male peacocks displaying their tail feathers to a group of peahens. Peacock A has a large, vibrant tail with many eyespots; Peacock B has a smaller, duller tail. The peahens are shown moving toward Peacock A.

Define differential reproduction. [1]

Explain how the concept of biological fitness applies to Peacock A and Peacock B in this diagram. [1]

Explain why the trait of having a large, colourful tail is likely to become more common in the peacock population over many generations. [2]

Solutions

14QuestionDifferential Reproduction and FitnessAssessment Practice

7 marks~11 minCriterion B

A population of mice lives in a forest with dark soil. Fur colour is controlled by a single gene: allele

D

(dark fur) is dominant over allele

d

(light fur). Over 10 years, the habitat gradually transitions to grassland with light-coloured soil. Allele frequencies recorded across three generations are shown below.

Generation	1	2	3
$D$ allele frequency	0.90	0.75	0.55

Describe the trend in the frequency of the

D

allele across the three generations. [2]

Deduce the approximate frequency of the

D

allele in generation 4, justifying your reasoning with reference to the data. [2]

Explain how differential reproduction and fitness account for the observed change in

D

allele frequency as the habitat shifts from forest to grassland. [3]

Solutions

15QuestionDifferential Reproduction and FitnessAssessment Practice

3 marks~5 minCriterion A

During a drought year on a Galápagos island, small soft seeds become scarce, leaving large hard seeds as the dominant food source. The bar chart below shows the average number of offspring produced by three beak phenotypes in a finch population during this drought year.

Beak phenotype — Average offspring produced
Wide: 5.5
Medium: 3.0
Narrow: 1.5

State which beak phenotype has the highest fitness during this drought year, and identify the average number of offspring it produces. [1]

Explain why wide-beaked finches are better able to survive and reproduce during a drought year. [1]

Analyse how the pattern of reproductive output shown in the data supports the concept of differential reproductive success as a mechanism of natural selection. [1]

Solutions

16QuestionProcess of Natural Selection (Variation, Overproduction, Competition, Survival of the Fittest, Reproduction, Change Over Time)Assessment Practice

8 marks~12 minCriterion C

A population of 10,000 Escherichia coli bacteria was exposed to a sub-lethal concentration of the antibiotic ciprofloxacin. Population size was recorded every two generations over ten generations.

Generation	0	2	4	6	8	10
Population size	10	000 — 2	000 — 500 — 1	000 — 5	000 — 12	000

Describe the trend in population size across the ten generations. [2]

Explain how the observed population trend provides evidence for natural selection. In your answer, refer to variation, overproduction, competition, survival of the fittest, and reproduction. [4]

Evaluate whether mutation alone, without natural selection, could account for the speed and consistency of the population recovery seen after generation 4. [2]

Solutions

17QuestionRole of Environmental Factors in SelectionAssessment Practice

4 marks~6 minCriterion C

Two populations of mice live in different habitats. Population A inhabits light-coloured sandy soil; Population B inhabits dark volcanic rock. Both populations contain individuals with light fur and individuals with dark fur. Birds of prey hunt by sight in both habitats.

Identify which fur colour is favoured by natural selection in Population A and explain why individuals with that phenotype have greater reproductive success. [2]

A student claims that, over many generations, dark-fur alleles will eventually disappear entirely from Population A. Evaluate this claim, using your knowledge of natural selection and population genetics. [2]

Solutions

18QuestionRole of Environmental Factors in SelectionAssessment Practice

2 marks~3 minCriterion D

In several countries, antibiotics are routinely added to livestock feed to promote growth and prevent infection. Bacteria naturally vary in their sensitivity to antibiotics; resistant individuals survive, reproduce, and pass on resistance genes, while non-resistant bacteria are eliminated.

Describe how this farming practice drives the natural selection of antibiotic-resistant bacteria. [1]

Explain one ethical issue that arises specifically from this practice. [1]

Solutions

19QuestionDifferential Reproduction and FitnessAssessment Practice

6 marks~9 minCriterion D

A farmer applies low-dose antibiotics as growth promoters in livestock. Resistant bacteria survive and reproduce at higher rates than non-resistant bacteria, generating a reservoir of antibiotic-resistant strains on the farm. Manure runoff carries these bacteria into adjacent soil and waterways.

Explain how antibiotic-resistant bacteria spread from the farm into surrounding soil and water sources. [2]

Apply your understanding of natural selection to explain why antibiotic-resistant bacterial populations are likely to increase further once they enter a contaminated local water supply. [2]

Evaluate the ethical tensions between the agricultural benefits of low-dose antibiotic use and the public health risks it creates for nearby communities. [2]

Solutions

20QuestionPhysiological AdaptationsAssessment Practice

5 marks~8 minCriterion B

A biologist measures oxygen consumption in a freshwater fish at five controlled water temperatures. The results are recorded below.

Temperature (°C)	10	15	20	25	30
Oxygen consumption (mg $\text{O}_2$ /kg/h)	50	75	110	155	210

Describe the trend in oxygen consumption as water temperature increases. [1]

Explain how water temperature affects metabolic rate in fish, using the data to support your answer. [2]

A colleague claims that oxygen consumption at 35°C will be exactly 265 mg

\text{O}_2

/kg/h, calculated by adding the same increase as the 25–30°C interval. Analyse whether this prediction is well-reasoned, and propose a more justified value with clear reasoning. [2]

Solutions

21QuestionAdaptation to Changing EnvironmentsAssessment Practice

2 marks~3 minCriterion A

Polar bears (Ursus maritimus) survive in Arctic environments where air temperatures regularly fall below −30 °C and sea ice provides the primary hunting ground.

Explain how the blubber layer helps a polar bear survive in its cold Arctic environment. [1]

A polar bear's large paws and its thick fur both contribute to survival on sea ice. Explain how each structure serves a different function, and suggest which adaptation is more critical for a bear actively hunting on ice. Justify your answer. [1]

Solutions

22QuestionAdaptation to Changing EnvironmentsAssessment Practice

5 marks~8 minCriterion D

In a controlled experiment, 50 stick insects (Extatosoma tiaratum) were placed on a matching background (green leaves) and 50 on a non-matching background (brown soil). Cumulative predation events were recorded over 10 days.

Day 2	matching = 2	non-matching = 8
Day 4	matching = 5	non-matching = 18
Day 6	matching = 9	non-matching = 30
Day 8	matching = 14	non-matching = 42
Day 10	matching = 20	non-matching = 50

State the total percentage of matching-background insects predated by Day 10. [1]

Explain how the data support the hypothesis that cryptic coloration provides a survival advantage. [2]

Evaluate the extent to which this experiment's design allows the conclusion to be applied to natural environments. [2]

Solutions

23QuestionAdaptation to Changing EnvironmentsAssessment Practice

5 marks~8 minCriterion C

A student states: "When bacteria are exposed to an antibiotic, the antibiotic causes mutations in some bacterial cells, and those mutated cells survive and reproduce, leading to antibiotic resistance."

Hospitals worldwide report rising rates of antibiotic-resistant infections, making this mechanism clinically significant.

Identify the specific error in the student's statement. [1]

Explain the correct mechanism by which antibiotic resistance develops in a bacterial population. [2]

Evaluate how this mechanism illustrates the role of genetic variation and natural selection in adaptation to a changing environment. [2]

Solutions

24QuestionAdaptation to Changing EnvironmentsAssessment Practice

7 marks~11 minCriterion D

A conservation organisation is considering using CRISPR gene editing to introduce heat-tolerant genes from thermally resistant corals into Great Barrier Reef populations, aiming to improve survival under rising ocean temperatures. Critics warn of unintended ecological consequences, ethical concerns about overriding natural selection, and the difficulty of forecasting outcomes in a system already stressed by ocean acidification and bleaching events.

Discuss TWO potential ecological risks of releasing genetically modified corals into the reef ecosystem. [3]

Discuss ONE ethical concern raised by using CRISPR to deliberately alter the evolutionary trajectory of a wild coral population. [2]

Evaluate the limitations of predicting the long-term impacts of this intervention on reef biodiversity. [2]

Solutions

25QuestionPhysiological AdaptationsAssessment Practice

3 marks~5 minCriterion C

The diagram shows a fish gill filament in cross-section. Water flows over the filament from left to right; blood flows through the capillaries from right to left. Dissolved oxygen concentrations (arbitrary units) at three positions along the filament are shown below.

Position — Water O₂ / Blood O₂
Entry (left): 100 / 60
Middle: 75 / 40
Exit (right): 50 / 20

Identify the term for the exchange system in which two fluids flow in opposite directions. [1]

Explain how the opposite flow directions maintain a concentration gradient along the entire length of the filament. [1]

Evaluate what would happen to oxygen uptake efficiency if blood and water flowed in the same direction, using the data provided to support your answer. [1]

Solutions

26QuestionAdaptation to Changing EnvironmentsAssessment Practice

4 marks~6 minCriterion A

Two populations of the same bird species live on separate islands. Island 1 has abundant hard-shelled seeds and very few insects. Island 2 has abundant soft-bodied insects and very few hard seeds. Over many generations, the populations have developed distinctly different beak morphologies.

Identify the beak morphology present on Island 1 and explain how it increases the survival rate of birds in that environment. [2]

The two island populations were once a single interbreeding population. Analyse how the different food sources on each island could have driven the divergence in beak morphology over successive generations. [2]

Solutions

27QuestionFossil Record and Evolutionary HistoryAssessment Practice

6 marks~9 minCriterion B

Three transitional fossils document the fish-to-tetrapod transition:

Fossil A — Tiktaalik (~375 Ma): possesses wrist bones and neck vertebrae, but retains fin rays.
Fossil B — Acanthostega (~365 Ma): possesses distinct digits and neck vertebrae, but retains fin rays and limbs not fully adapted for weight-bearing.
Fossil C — Ichthyostega (~360 Ma): possesses well-developed, weight-bearing limbs and robust neck vertebrae, with greatly reduced fin rays.

For each fossil, identify one skeletal feature that supports the hypothesis that tetrapods evolved from lobe-finned fish. [3]

Tiktaalik and Acanthostega each retain fin rays despite possessing tetrapod features. Explain what this pattern of trait retention reveals about the nature of the fish-to-tetrapod transition. [1]

Evaluate whether this fossil sequence provides strong or weak support for the hypothesis that tetrapods evolved from lobe-finned fish. Justify your reasoning using evidence from all three fossils. [2]

Solutions

28QuestionBiogeography and Species DistributionAssessment Practice

3 marks~5 minCriterion C

The bar graph below shows the number of endemic bird species recorded on four Pacific islands of different land areas: Guam (549 km²), Fiji (18 274 km²), New Caledonia (18 575 km²), and Hawaii (28 313 km²).

Describe the relationship between island area and number of endemic bird species shown in the graph. [1]

Explain how greater habitat diversity on larger islands increases the number of endemic species. [1]

Analyse how geographic isolation within large islands drives adaptive radiation, and assess whether island area alone is sufficient to explain differences in endemic species richness. [1]

Solutions

29QuestionBiogeography and Species DistributionAssessment Practice

2 marks~3 minCriterion D

Madagascar's eastern rainforest exists as fragmented patches separated by degraded land. Conservation planners are proposing a wildlife corridor to reconnect these fragments.

Explain how the theory of island biogeography supports the use of a wildlife corridor to increase species richness in Madagascar's fragmented rainforest. [1]

Identify one ethical issue that could arise from establishing this corridor, and explain why it presents a conflict for conservation planners. [1]

Solutions

30QuestionBiogeography and Species DistributionAssessment Practice

8 marks~12 minCriterion D

The Wallace Line runs through a deep-water channel separating Bali and Lombok in Indonesia. Even when sea levels dropped 120 m during the last ice age, land bridges formed west of the line but the deep channel remained unbridged.

Native family counts per island:

Bali (west): Mammals 35 · Birds 120 · Reptiles 60
Lombok (east): Mammals 15 · Birds 110 · Reptiles 55

Identify the pattern in species distribution shown by the data above. [2]

A fossil marsupial is discovered on one of the islands. Deduce which side of the Wallace Line it most likely came from, using the ice-age sea-level data to support your reasoning. [3]

Justify why marsupials are found on one side of the Wallace Line and not the other, by analysing the roles of plate tectonic history and the deep-water channel as a dispersal barrier. [3]

Solutions

31QuestionBiogeography and Species DistributionAssessment Practice

12 marks~18 minCriterion C

The diagram below shows the global distribution of marsupial species, with shading indicating species richness across continents.

Use the diagram and your knowledge of biogeography and evolution to answer the following questions.

Describe the distribution pattern of marsupial species shown in the diagram. [2]

Explain how the presence of marsupials on both Australia and South America supports the concept of common descent. [3]

Analyse how the breakup of the supercontinent Gondwana accounts for the current distribution of marsupials, including why Australian and South American marsupials have diverged so markedly from one another. [4]

Evaluate the reliability of biogeographical evidence alone for establishing evolutionary relationships between species, referring to at least one specific complicating factor. [3]

Solutions

32QuestionComparative Anatomy and Homologous StructuresAssessment Practice

3 marks~5 minCriterion A

The diagram shows the forelimb bones of a human, a whale, and a bat, each labelled with the following bones: humerus, radius, ulna, carpals, metacarpals, and phalanges.

Identify any two of the three vertebrates that have homologous forelimb structures. [1]

Explain how the presence of the same set of bones in the forelimbs of all three vertebrates provides evidence for their common evolutionary origin, despite each forelimb serving a different function. [2]

Solutions