O Level Biology Evolution Diversity Quiz

O-Level Biology Quiz - Evolution Diversity: Answer Key

Total Marks: 40
Topic: Evolution Diversity (syllabus-first, AI-generated from Stage 4 inferred patterns; not claimed as past-year derived)

1. [1] Natural selection is driven by environmental pressures without human intervention, whereas artificial selection is driven by humans choosing desirable traits for breeding.
Teaching note: Natural selection = survival of fittest in nature; artificial = e.g. dog breeding by humans.

2. [1] Example: forelimb of whale (used for swimming) and forelimb of human (used for grasping). Both are homologous.
Accept any valid mammal pair with functions.

3. [1] A species is a group of organisms that can interbreed and produce fertile offspring in nature.
Teaching note: Biological species concept focuses on reproductive isolation.

4. [1] Charles Darwin.

5. [1] Fossils show intermediate forms / show changes in structure over geological time.
e.g. Archaeopteryx shows link between reptiles and birds.

6. [4]

• Random mutation creates variation in bacteria, some are resistant [1]
• Antibiotic kills non-resistant bacteria [1]
• Resistant bacteria survive and reproduce [1]
• Over time resistant allele frequency increases in population [1]
  Marking: 1 per point. Common mistake: saying bacteria "develop" resistance on purpose.

7. [2]

• Bacterial cell has peptidoglycan cell wall; animal cell has no wall [1]
• Bacterial cell has plasmids; animal cell does not [1]
  Accept: nucleoid vs nucleus, 70S vs 80S ribosomes.

8. [3]

• Environment changed to brown soil, brown beetles camouflaged [1]
• Green beetles more visible to predators, eaten more [1]
• Brown beetles survived, reproduced, passing brown allele [1]
  Based on Q8-fig1: before 6G/4B, after 2G/8B shows shift.

9. [4]

• Convergent: unrelated species develop similar traits due to similar environment [1+1 e.g. dolphin & shark shape]
• Divergent: related species become different due to different environments [1+1 e.g. finches' beaks]
  Marking: definition + example each.

10. [4]

• Population split by physical barrier (river, mountain) [1]
• No gene flow between groups [1]
• Different selection pressures in each area [1]
• Accumulation of differences leads to reproductive isolation [1]

11. [2]

• Comparative anatomy (homologous structures) [1]
• Molecular evidence (DNA/protein similarity) [1]
  Accept embryology, biogeography.

12. [3]

• Homologous structures have same basic bone layout [1]
• Suggest inherited from common ancestor [1]
• Modified for different functions in different species [1]

13. [3]

• Drought reduced small seeds, only large hard seeds left [1]
• Birds with deeper beaks could crack them, survived [1]
• Passed trait to offspring, mean depth increased (9.2→11.0 mm) [1]
  From Q13-fig1 bar increase.

14. [2]

• Mutation [1]
• Sexual reproduction / recombination [1]
  Accept gene flow.

15. [3]

• Low variation = fewer traits to adapt to change [1]
• Environmental change may kill most/all [1]
• Less chance of resistant individuals surviving [1]

16. [2]

• Species A and B most closely related [1]
• Fewest amino acid differences (3) [1]
  Teaching: fewer differences = more recent common ancestor.

17. [1] Species D (18 differences from A).

18. [1] X and Y (share most recent node in Q18-fig1).

19. [2]

• Shorter branch / recent node = closer relation [1]
• Tree shows divergence order from common ancestor [1]

20. [3]

• Insecticide is selection pressure [1]
• Resistant mosquitoes survived, bred [1]
• Frequency of resistance allele rose to 80% [1]
  Common mistake: thinking insecticide created mutation, not selected it.