IB Biology SL A4.1 Evolution and speciation Questions

Practise IB Biology SL A4.1 with questions on variation, natural selection, speciation, adaptation and changes in biodiversity.

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

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam analysis

SL · 2010–2025
Papers with this topic41 / 141in the analysed sample
Latest appearanceNovember 2025
Tagged question parts51
Paper types5

Most tested objectives

  1. A4.1.4—Evidence from homologous structures11 papers
  2. A4.1.5—Convergent evolution11 papers
  3. A4.1.1—Evolution as change in heritable characteristics8 papers
  4. A4.1.2—Evidence from sequences7 papers
  5. A4.1.7—Reproductive isolation and differential selection6 papers

Common question formats

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

Recent exam appearances

November 2025Paper 2 SL · TZ1Q7(a)[ 4 ]
November 2025Paper 1A SL · TZ1Q22[ 1 ]
May 2025Paper 2 SL · TZ3Q3(b)[ 3 ]

141 papers analysed · Tagging incomplete

Exam points

  • Define evolution as cumulative change in heritable population characteristics, then explain how inherited variation and differential reproductive success change populations over generations.
  • Use DNA, RNA, amino-acid or protein sequence identity and differences to infer common ancestry, phylogeny and divergence.
  • Explain how selective breeding retains heritable variation to change inherited characteristics over generations, using dog, cattle or crop examples.
  • Distinguish homologous and analogous structures by origin, underlying structure and function, and use pentadactyl anatomy to infer common ancestry and divergent evolution.
  • Compare convergent and divergent evolution using ancestry, environments and selection pressures, identifying analogous wings, eyes or other independently evolved structures.
  • Explain how geographic or reproductive isolation, mutation, selection and time change gene pools toward formation of new species.
  • Identify prezygotic and postzygotic barriers that prevent gene flow between populations.
  • Evaluate breeding probabilities, population or allele-frequency data as evidence for reproductive isolation and speciation.

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 selection

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]

What is evolution?

A

Change in the heritable characteristics of a species

B

Change in the phenotype of a species

C

Speciation due to geographical separation

D

Survival of the fittest

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: 1]

The cladogram shows the evolutionary relationships between humans and four other vertebrate species based on the comparison of the protein myoglobin.

Figure for Question 1 — IB Biology SL

Which feature of the myoglobin molecules might have been compared to produce the cladogram?

A

Differences in their 3D shape

B

Differences in amino acid composition

C

Similarities in base sequences

D

Similarities in function

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: 1]

Humans have been improving crop species for thousands of years by cross-breeding plants with desirable characteristics. The photograph shows the changes in dry cobs of corn (Zea mays) over 10000 years.

Figure for Question 1 — IB Biology SL

What is the name of the process that was used to produce modern corn?

A

Selective breeding

B

Adaptive radiation

C

Discontinuous variation

D

Natural selection

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]

The image shows the wings of an insect, bird and bat.

Insect

Insect

Bird

Bird

Bat

Bat

The bird and bat wings share homologous bone structures whereas the insect wing does not. Outline the conclusion that can be drawn about the evolution of these wings, based on homologous structures.

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]

The images show an ichthyosaurus and a dolphin. Ichthyosaurus is an extinct aquatic reptile, known only from fossil remains. Dolphins are mammals.

Figure for Question 1 — IB Biology SL

How have these species evolved?

A

Their streamlined bodies show divergent evolution.

B

Their streamlined bodies are analogous structures.

C

Their pentadactyl limbs are an example of convergent evolution.

D

Their pentadactyl limbs are analogous structures.

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: 3]

Scientists examined the teeth of a group of related species of cichlid fishes in Lake Tanganyika, Africa, to determine their evolutionary relationship. The group contains six species from two genera, Perissodus and Haplotaxodon. The chart shows the number of teeth per jaw of these species and indicates whether each is adapted to feed in shallow water or deep water. Species from the genus Perissodus are known for their unique feeding habit of eating the scales of other fish.

Figure for Question 1 — IB Biology SL

Key: ○ upper jaw • lower jaw □ shallow water ! deep water

P. elaviae and H. microlepis both evolved from a common ancestor. Suggest how they became different 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: 1]

Bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) are primates.

Bonobo (Pan paniscus)

Bonobo (Pan paniscus)

Chimpanzee (Pan troglodytes)

Chimpanzee (Pan troglodytes)

Separation by the Congo River allowed these two species to be formed. What was a consequence of the separation?

A

Natural selection

B

Reproductive isolation

C

Selective breeding

D

Analogous structures