IMO Practice Test — Heredity
6 Questions • 15 min • Olympiad level
15:00
Question 1 of 6
Two heterozygous tall pea plants (Tt) are crossed. The chance that an offspring is short (tt) is:
1 in 4
1 in 2
3 in 4
0
Explanation: Tt x Tt gives 1 TT : 2 Tt : 1 tt, so 1 in 4 offspring are short (tt).
Question 2 of 6
A couple has three daughters. The chance that their fourth child is a son is:
About 1 in 2 (50%)
Certain to be a son
Impossible
1 in 4
Explanation: Each birth is independent with a 50:50 chance, decided by the father's X or Y sperm.
Question 3 of 6
Why does a recessive trait reappear in the F₂ generation though it was absent in F₁?
Each plant carries two factors; in F2 some get two recessive factors
New genes are created in F2
The dominant gene is destroyed
It is an acquired trait
Explanation: Factors separate and recombine; some F2 individuals inherit two recessive alleles, so the trait shows again.
Question 4 of 6
The bones of a human arm and a bat's wing have a similar basic plan. This is evidence that they:
Share a common ancestor
Have no relationship
Are acquired traits
Cannot evolve
Explanation: Homologous structures with a common basic plan point to a shared ancestor (evidence for evolution).
Question 5 of 6
Fossils are useful in the study of evolution because they:
Show what organisms of the past looked like and how life changed
Are living organisms
Are acquired traits
Determine sex
Explanation: Fossils are preserved remains that reveal past life forms and the gradual change over time.
Question 6 of 6
Natural selection leads to evolution because, over generations:
Organisms with helpful inherited variations survive and reproduce more
Acquired traits are passed on
All variations disappear
Genes never change
Explanation: Nature 'selects' individuals with useful inherited variations, so those traits become more common.