IMO Practice Test — Human Reproduction
6 Questions • 15 min • Olympiad level
15:00
Question 1 of 6
A sperm's middle piece is packed with mitochondria because it must:
Provide energy for the tail to swim
Carry the genes
Digest the egg
Store food for the baby
Explanation: Mitochondria supply the ATP needed to power the sperm's tail movement toward the egg.
Question 2 of 6
If fertilisation does NOT occur in a cycle, the thickened uterine lining is:
Shed as the menstrual flow
Kept permanently
Turned into an egg
Absorbed by the ovary
Explanation: Without a fertilised egg to implant, the lining breaks down and is shed during menstruation.
Question 3 of 6
The zygote is diploid even though the gametes are haploid because fertilisation:
Combines the chromosomes of both gametes
Halves the chromosomes
Removes chromosomes
Copies one gamete only
Explanation: Joining two haploid sets restores the full diploid chromosome number in the zygote.
Question 4 of 6
The placenta is described as the baby's lifeline because it carries out exchange of:
Nutrients, oxygen and wastes between mother and baby
Only bones
Only sperm
Nothing
Explanation: Across the placenta the baby gains O₂ and nutrients and gives up CO₂ and wastes.
Question 5 of 6
Colostrum, the first breast milk, is especially valuable to a newborn because it is rich in:
Antibodies that protect against infection
Sugar only
Bones
Sperm
Explanation: Colostrum supplies antibodies that give the newborn early immunity.
Question 6 of 6
Only one sperm normally fertilises an egg; mechanisms blocking extra sperm prevent the zygote from becoming:
Abnormal with too many chromosomes
Too small
Haploid
An egg
Explanation: Allowing several sperm would give an extra set of chromosomes, producing an abnormal, non-viable zygote.