IMO Practice Test — Evolution
7 Questions • 15 min • Olympiad level
15:00
Question 1 of 7
Homologous organs point to common ancestry, while analogous organs point to:
Convergent evolution toward a similar function
Common ancestry
No evolution
Identical genes
Explanation: Different structures evolving the same function (e.g. wings) reflect convergence, not shared ancestry.
Question 2 of 7
Overuse of antibiotics speeds up the spread of resistant bacteria because antibiotics act as a:
Selection pressure favouring resistant individuals
Source of food
Mutation maker on demand
Cause of extinction of all bacteria
Explanation: Killing susceptible bacteria leaves resistant ones to multiply — natural selection in action.
Question 3 of 7
Lamarck's giraffe explanation fails because the longer neck gained by stretching during life is:
Not passed on to offspring
Always inherited
A mutation
Caused by selection
Explanation: Acquired characters do not change the genes, so they are not inherited — unlike heritable variation.
Question 4 of 7
The near-identical structure of forelimb bones in humans, whales and bats is best explained by:
Descent from a common ancestor
Pure chance
Identical diets
Living in the same place
Explanation: A shared underlying plan adapted to different uses indicates common ancestry (divergent evolution).
Question 5 of 7
Bipedalism (walking upright) was important in human evolution mainly because it:
Freed the hands for making and using tools
Reduced brain size
Removed the need for food
Stopped variation
Explanation: Standing upright freed the hands, allowing tool use that drove further development.
Question 6 of 7
Random change in the gene frequencies of a small population, independent of fitness, is called:
Genetic drift
Natural selection
Mutation
Transcription
Explanation: Genetic drift is chance fluctuation in allele frequencies, strongest in small populations.
Question 7 of 7
If the allele frequencies in a population are found to be changing over generations, it indicates that:
Evolution is occurring (an evolutionary force is acting)
The population is at equilibrium
No genes exist
Mating has stopped
Explanation: A departure from Hardy-Weinberg equilibrium signals that an evolutionary force is at work.