IB Biology HL A4.1 Evolution and speciation Questions

Practise IB Biology HL A4.1 with evidence-led questions on variation, selection pressure, adaptation, speciation and population change.

92 questions in this syllabus scope, with question parts counted together.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam analysis

HL · 2010–2025
Papers with this topic38 / 117in the analysed sample
Latest appearanceNovember 2025
Tagged question parts45
Paper types5

Most tested objectives

  1. A4.1.11 (HL)—Abrupt speciation in plants9 papers
  2. A4.1.4—Evidence from homologous structures7 papers
  3. A4.1.7—Reproductive isolation and differential selection6 papers
  4. A4.1.6—Speciation by splitting of pre-existing species5 papers
  5. A4.1.2—Evidence from sequences4 papers

Common question formats

  • Definition or recall
  • Process explanation
  • Data analysis
  • Comparison
  • Evaluation

Recent exam appearances

November 2025Paper 1A HL · TZ3Q33[ 1 ]
May 2025Paper 2 HL · TZ3Q8(c)[ 4 ]
May 2025Paper 2 HL · TZ2Q9(a)[ 4 ]

117 papers analysed · Tagging incomplete

Exam points

  • Define evolution as heritable change in populations and explain how selective breeding changes inherited characteristics over generations.
  • Use DNA, RNA, amino-acid or protein sequence similarities and differences to infer common ancestry, phylogeny or divergence.
  • Distinguish homologous and analogous structures and compare divergent with convergent evolution using ancestry, function, environments and selection pressures.
  • Explain how isolation, differential selection and prezygotic or postzygotic barriers produce speciation, distinguishing allopatric and sympatric pathways.
  • Explain adaptive radiation as divergence from one ancestor into ecological niches.
  • Explain how polyploidy and chromosome doubling can cause abrupt plant speciation, reproductive isolation and restored fertility.

Covered syllabus points

A4.1.1—Evolution as change in heritable characteristicsA4.1.2—Evidence from sequencesA4.1.3—Evidence from selective breedingA4.1.4—Evidence from homologous structuresA4.1.5—Convergent evolutionA4.1.6—Speciation by splitting of pre-existing speciesA4.1.7—Reproductive isolation and differential selectionA4.1.8 (HL)—Sympatric vs. allopatric speciationA4.1.9 (HL)—Adaptive radiationA4.1.10 (HL)—Barriers to hybridizationA4.1.11 (HL)—Abrupt speciation in plants

Exam points

  • Define evolution as cumulative change in the heritable characteristics of a population.
  • Explain that acquired characteristics are not inherited in the Darwinian sense.

Question 1

[Maximum number: 1]

Which statement best describes how evolution occurs?

A

Species which produce the most offspring are favoured by natural selection.

B

Mutations in somatic cells are passed on to offspring.

C

Natural selection decreases the frequency of unfavourable characteristics.

D

Changes in species lead towards greater complexity over time.

Exam points

  • Use the universality of DNA, the genetic code, ATP use and core metabolism as evidence for common ancestry.
  • Compare DNA, RNA and protein sequence differences to infer relatedness and evolutionary divergence.

Question 1

[Maximum number: 6]

Discuss how variations in proteins can indicate phylogeny and be used as an evolutionary clock.

Exam points

  • Explain how selective breeding shows that traits can change rapidly under selection.
  • Use pigeons, domesticated animals, Brassica crops, wheat or maize as examples of selective breeding.

Question 1

[Maximum number: 3]

Cell biologists play an important role in research into disease, fertility, evolution and many other areas of science.

Outline the evidence for evolution provided by selective breeding.

Exam points

  • Explain that homologous structures share a common ancestry even when their functions differ.
  • Use vertebrate pentadactyl limbs as evidence for divergent evolution and adaptive radiation.

Question 1

[Maximum number: 1]

What are the evolutionary origins and functions of homologous structures?

Evolutionary origin

Function

common or different origin

same function

common origin

same or different function

different origin

same function

different origin

same or different function

Exam points

  • Describe analogous structures as having similar functions but different evolutionary origins.
  • Explain how similar selection pressures can produce convergent evolution.
  • Use bat and insect wings as an example of analogous structures produced by convergence.

Question 1

[Maximum number: 1]

What is the evolutionary origin and function of analogous structures in living organisms?

Evolutionary origin

Function

different origin

similar function

different origin

same or different function

same or different origin

same function

same origin

different function

Exam points

  • Explain that speciation forms new species by splitting a pre-existing species.
  • Explain how isolated gene pools diverge through selection, mutation and genetic drift.

Question 1

[Maximum number: 1]

The map shows the distribution of chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) on either side of the Congo River as it flows towards the Atlantic Ocean in the Democratic Republic of Congo. Bonobos occupy the dense wet forest south of the Congo River, whereas chimpanzees occupy a forested habitat north of the river. Both species are descended from a common ancestor.

Figure for Question 1 — IB Biology HL

State the type of speciation shown by the two species.

Exam points

  • Explain how reproductive isolation reduces gene flow and allows populations to diverge.
  • Explain how geographic separation and different selection pressures can drive speciation.
  • Use river-linked isolation and divergence of chimpanzees and bonobos as an example.

Question 1

[Maximum number: 7]

Explain how speciation occurs, including the different processes of isolation and selection.

Exam points

  • Distinguish allopatric speciation by geographic isolation from sympatric speciation without spatial separation.
  • Compare temporal, behavioural or intrinsic barriers that can separate sympatric populations.

Question 1

[Maximum number: 1]

Some species could potentially hybridize but never do in the wild. What could be an example of temporal isolation?

A

Different song patterns by grasshoppers of the genus Chorthippus

B

Sage plants Salvia apiana and Salvia mellifera, pollinated by different species of insects

C

Cicadas Magicicada tredecim become sexually mature every 13 years and Magicicada septedecim every 17 years

D

Pygmy three-toed sloths (Bradypus pygmaeus), isolated on the island of Escudo de Veraguas from mainland sloths

Exam points

  • Explain how adaptive radiation produces related species from one ancestor as populations diverge into different ecological niches.
  • Use Darwin’s finch beak adaptations to illustrate how populations adapt to different feeding niches.

Question 1

[Maximum number: 3]

Evolution causes gene pools to change over time and new species to be formed.

Outline how adaptive radiation provides evidence for evolution.

Exam points

  • Classify habitat, temporal and behavioural isolation as prezygotic barriers to hybridization.
  • Explain how inviable or infertile hybrids, such as mules, are postzygotic barriers.

Question 1

[Maximum number: 1]

Two kinds of wolf spider rub specialized body parts together in order to produce distinct sounds to attract females. Females of both groups will only allow a male of the same kind to mate with them. It has been found through experimentation, however, that offspring can be produced from crossings between the two groups. What can be hypothesized?

I. The groups are reproductively isolated.
II. They could be the same species.
III. This is an example of behavioural isolation.

A

I only

B

II only

C

I and II only

D

I, II and III

Exam points

  • Explain how polyploidy can cause abrupt reproductive isolation in plants.
  • Explain how autopolyploidy and allopolyploidy can produce fertile new plant lineages.
  • Use Persicaria hybridisation to illustrate plant speciation through chromosome change.

Question 1

[Maximum number: 1]

What is a possible cause of abrupt speciation?

A

Polygenic inheritance

B

Polymorphism

C

Polyploidy

D

Polyspermy