Noesis
Level 1 — RecognitionPopulation Genetics & Speciation

Population Genetics & Speciation

⏱ 20 minutes30 marksprintable — key stays hidden on paper

Level 1: Recognition (MCQ + Matching + True/False with Justification)

Time Limit: 20 minutes Total Marks: 30

Section A — Multiple Choice (1 mark each) — 10 marks

Choose the single best answer.

Q1. The Hardy-Weinberg equation p2+2pq+q2=1p^2 + 2pq + q^2 = 1 represents the sum of:

  • A) allele frequencies
  • B) genotype frequencies
  • C) mutation rates
  • D) migration rates

Q2. Which of the following is NOT an assumption of the Hardy-Weinberg principle?

  • A) No mutation
  • B) Random mating
  • C) Natural selection acting on the population
  • D) No gene flow

Q3. A random reduction in population size due to a natural disaster killing individuals indiscriminately is an example of:

  • A) Founder effect
  • B) Bottleneck effect
  • C) Gene flow
  • D) Directional selection

Q4. According to the biological species concept, members of the same species are defined by their ability to:

  • A) look identical
  • B) live in the same habitat
  • C) interbreed and produce fertile offspring
  • D) share the same number of chromosomes

Q5. Speciation that occurs when a population is divided by a geographic barrier is termed:

  • A) sympatric
  • B) allopatric
  • C) parapatric (ignore)
  • D) polyploid

Q6. A hybrid such as a mule being sterile is an example of which reproductive isolation mechanism?

  • A) Prezygotic — temporal isolation
  • B) Prezygotic — behavioural isolation
  • C) Postzygotic — hybrid sterility
  • D) Prezygotic — mechanical isolation

Q7. In a Hardy-Weinberg population, if the frequency of the recessive allele q=0.2q = 0.2, the frequency of homozygous recessive individuals is:

  • A) 0.04
  • B) 0.16
  • C) 0.32
  • D) 0.20

Q8. The primary ultimate source of all new genetic variation is:

  • A) recombination
  • B) mutation
  • C) gene flow
  • D) genetic drift

Q9. The idea that evolution occurs in rapid bursts separated by long periods of little change is called:

  • A) gradualism
  • B) punctuated equilibrium
  • C) coevolution
  • D) convergent evolution

Q10. In a phylogenetic tree, a node represents:

  • A) an extinct species only
  • B) a common ancestor from which lineages diverge
  • C) a geographic barrier
  • D) a mutation event

Section B — Matching (1 mark each) — 8 marks

Match each term in Column X to its correct description in Column Y. Write the letter.

Column X Column Y
Q11. Founder effect A. Movement of alleles between populations by migration
Q12. Gene flow B. Both structures for reproduction and the offspring's inviability before development
Q13. Postzygotic barrier C. New population started by a few individuals carrying a subset of alleles
Q14. Miller–Urey experiment D. Grouping organisms by shared derived characteristics
Q15. Cladistics E. Reduced hybrid fitness after fertilisation
Q16. Prezygotic barrier F. Simulated formation of organic molecules from inorganic precursors
Q17. Allele frequency G. Barrier preventing mating or fertilisation
Q18. Genetic drift H. Proportion of a specific allele among all alleles at a locus
I. Random change in allele frequencies in small populations

(Note: Column Y has one extra option that is not used.)

Section C — True/False with Justification (2 marks each: 1 T/F + 1 justification) — 12 marks

Q19. "A population that is evolving is in Hardy-Weinberg equilibrium." True or False? Justify.

Q20. "Genetic drift has a greater effect on large populations than on small populations." True or False? Justify.

Q21. "Sympatric speciation can occur without any physical geographic barrier." True or False? Justify.

Q22. "Most mutations are immediately beneficial and drive adaptation." True or False? Justify.

Q23. "Behavioural isolation (differences in courtship signals) is a postzygotic isolating mechanism." True or False? Justify.

Q24. "On a phylogenetic tree, taxa sharing a more recent common ancestor are more closely related." True or False? Justify.

Answer keyMark scheme & solutions

Section A — MCQ (1 mark each)

Q1. B — The three terms are genotype frequencies: p2p^2 (homozygous dominant), 2pq2pq (heterozygous), q2q^2 (homozygous recessive), summing to 1. (1)

Q2. C — HW equilibrium requires NO selection; natural selection changes allele frequencies, violating equilibrium. (1)

Q3. B — A bottleneck is a sharp, non-selective reduction in population size; the founder effect involves a few individuals colonising a new area, not a disaster. (1)

Q4. C — The biological species concept defines species by reproductive compatibility producing fertile offspring. (1)

Q5. B — Allopatric = "other homeland"; separation by a geographic barrier. (1)

Q6. C — The mule is viable but sterile → postzygotic hybrid sterility. (1)

Q7. A — q2=(0.2)2=0.04q^2 = (0.2)^2 = 0.04. (1)

Q8. B — Mutation creates new alleles; recombination and drift only reshuffle/redistribute existing variation. (1)

Q9. B — Punctuated equilibrium = rapid bursts + long stasis. (1)

Q10. B — A node marks a common ancestor at the point of lineage divergence. (1)

Section B — Matching (1 mark each)

  • Q11 → C (Founder effect: new population from few individuals) (1)
  • Q12 → A (Gene flow: alleles moving via migration) (1)
  • Q13 → E (Postzygotic: reduced hybrid fitness after fertilisation) (1)
  • Q14 → F (Miller–Urey: organic molecules from inorganic precursors) (1)
  • Q15 → D (Cladistics: grouping by shared derived characters) (1)
  • Q16 → G (Prezygotic: barrier before mating/fertilisation) (1)
  • Q17 → H (Allele frequency: proportion of an allele) (1)
  • Q18 → I (Genetic drift: random change in allele frequency) (1)

(Option B is the unused distractor.)

Section C — True/False with Justification (2 marks each)

Q19. FALSE (1) — HW equilibrium describes a non-evolving population where allele frequencies stay constant; if a population is evolving, at least one HW assumption is violated. (1)

Q20. FALSE (1) — Drift has a greater effect on small populations, where random sampling causes larger allele-frequency fluctuations; large populations buffer chance effects. (1)

Q21. TRUE (1) — Sympatric speciation arises within one geographic area via mechanisms like polyploidy, disruptive selection, or niche/mate preference — no physical barrier needed. (1)

Q22. FALSE (1) — Most mutations are neutral or harmful; only a small fraction are beneficial, and even those are not necessarily "immediate." (1)

Q23. FALSE (1) — Behavioural isolation prevents mating from occurring, so it acts before zygote formation → it is a prezygotic mechanism. (1)

Q24. TRUE (1) — Taxa sharing a more recent common ancestor (nearer node) diverged more recently and are more closely related. (1)

[
  {"claim":"Q7: q=0.2 gives q^2 = 0.04", "code":"q=0.2; result = (q**2 == 0.04)"},
  {"claim":"Q1/HW: with q=0.2, p2+2pq+q2 = 1", "code":"q=0.2; p=0.8; result = (p**2 + 2*p*q + q**2 == 1)"},
  {"claim":"HW heterozygote freq for q=0.2 is 0.32", "code":"q=0.2; p=0.8; result = (2*p*q == 0.32)"},
  {"claim":"HW dominant homozygote freq for q=0.2 is 0.64", "code":"q=0.2; p=0.8; result = (p**2 == 0.64)"}
]