Secondary 4 Pure Biology Evolution Diversity Quiz

Secondary 4 Pure Biology Quiz - Evolution Diversity

Answer Key and Marking Scheme

Total Marks: 50

Section A: Multiple Choice Questions (10 marks)

Marking: 1 mark per correct answer. Total = 10 marks.

Section B: Structured Questions (24 marks)

Question 11 (4 marks)

(a) [2 marks]

• These are homologous structures [1 mark].
• They indicate that these organisms share a common ancestor / are evolutionarily related, as the same basic bone arrangement has been modified for different functions [1 mark].

(b) [2 marks]

• Divergent evolution occurs when populations of a common ancestor evolve different traits to adapt to different environments/ways of life [1 mark].
• The pentadactyl limb has been modified from the ancestral structure into different forms (human hand for manipulation, cat paw for walking, whale flipper for swimming, bat wing for flying), demonstrating divergence from a common ancestral form [1 mark].

Question 12 (5 marks)

(a) [4 marks]

• Variation: There was genetic variation in the moth population, with both light and dark forms present [1 mark].
• Selection pressure: The darkening of tree trunks by soot meant light-coloured moths were more visible to predators (birds), while dark moths were better camouflaged [1 mark].
• Differential survival: Dark moths were more likely to survive and reproduce, while light moths were more likely to be eaten [1 mark].
• Inheritance: The dark moths passed their alleles for dark colouration to their offspring. Over generations, the frequency of the dark allele increased in the population [1 mark].

(b) [1 mark]

• Mutation (a random change in the DNA/gene controlling wing colour) [1 mark].

Question 13 (5 marks)

(a) [2 marks]

• The percentage of antibiotic-resistant bacteria increases after each course of antibiotics [1 mark].
• Between antibiotic courses, the percentage may remain stable or decrease slightly, but the overall trend is an increase in resistance over time [1 mark].

(b) [3 marks]

• Before antibiotic treatment, a small proportion of bacteria already possess resistance genes due to random mutations [1 mark].
• When antibiotics are administered, susceptible bacteria are killed, but resistant bacteria survive (the antibiotic acts as a selection pressure) [1 mark].
• The surviving resistant bacteria reproduce, passing their resistance genes to their offspring. With each course of antibiotics, the proportion of resistant bacteria increases [1 mark].

Question 14 (4 marks)

(a) [1 mark]

• The higher the percentage of DNA similarity, the more closely related the species are / the more recently they shared a common ancestor [1 mark].

(b) [1 mark]

• Most closely related: Chimpanzee (98.8% similarity) [0.5 marks].
• Most distantly related: Gibbon (94.7% similarity) [0.5 marks].

(c) [2 marks]

• DNA sequencing allows comparison of genetic material between different species [1 mark].
• Species that share a more recent common ancestor have more similar DNA sequences because there has been less time for mutations to accumulate. This pattern of molecular similarity supports the evolutionary relationships predicted by the theory of evolution [1 mark].

Question 15 (6 marks)

(a) [4 marks]

• Variation: There was genetic variation in beak shape and size within the ancestral finch population [1 mark].
• Different selection pressures: Different islands had different available food sources (e.g., large seeds, small seeds, insects, cactus flowers). Each food source favoured a different beak shape [1 mark].
• Differential survival and reproduction: Finches with beak shapes suited to the available food on their island were more likely to survive and reproduce, passing on their alleles for that beak shape [1 mark].
• Accumulation of changes: Over many generations, the populations on different islands accumulated different adaptations, leading to the evolution of distinct beak shapes and eventually different species [1 mark].

(b) [2 marks]

• Adaptive radiation is the rapid evolution of many diverse species from a single ancestral species [1 mark].
• The Galápagos finches diversified from a common ancestor into multiple species, each with beak shapes adapted to different ecological niches/food sources on different islands [1 mark].

Section C: Data-Based and Extended Response Questions (16 marks)

Question 16 (4 marks)

(a) [1 mark]

• The common ancestor at the node/reptile-like ancestor where the reptile and mammal lineages diverged [1 mark]. (Accept: the amniote common ancestor / the reptilian ancestor)

(b) [2 marks]

• Birds share a more recent common ancestor with reptiles than with mammals, as shown by their closer position on the phylogenetic tree [1 mark].
• Despite both being warm-blooded, birds and mammals evolved endothermy (warm-bloodedness) independently (convergent evolution). Birds inherited many other characteristics (e.g., scales on legs, egg-laying, skeletal features) from their reptilian ancestors [1 mark].

(c) [1 mark]

• Comparative anatomy / homologous structures / comparative embryology / vestigial structures / biogeography [1 mark]. (Accept any one valid type of evidence)

Question 17 (6 marks)

(a) [4 marks]

• Variation: Within the mosquito population, there was genetic variation. Some mosquitoes possessed alleles that conferred resistance to DDT due to random mutations [1 mark].
• Selection pressure: When DDT was applied, it acted as a strong selection pressure, killing susceptible mosquitoes [1 mark].
• Differential survival: Mosquitoes with resistance alleles survived the DDT application, while susceptible mosquitoes died [1 mark].
• Reproduction and inheritance: The surviving resistant mosquitoes reproduced, passing their resistance alleles to their offspring. Over many generations, the frequency of resistance alleles in the population increased, resulting in a DDT-resistant population [1 mark].

(b) [2 marks]

• The resistance alleles are already widespread in the population, so most mosquitoes carry them [1 mark].
• Resistant mosquitoes continue to reproduce, and any new susceptible individuals that arise (or migrate in) will be killed by DDT, maintaining the high frequency of resistance alleles. The resistance trait is heritable and will persist in the population [1 mark].

Question 18 (4 marks)

(a) [2 marks]

• Any two from: fossil record, comparative anatomy (homologous structures), comparative embryology, molecular evidence (DNA/protein sequences), vestigial structures, biogeography (distribution of species) [1 mark each, maximum 2 marks].

(b) [2 marks]

• Award marks for a clear explanation of how the chosen evidence supports evolution. Example for fossil record:
  • Fossils show that organisms have changed over time, with simpler organisms found in older rocks and more complex organisms in younger rocks [1 mark].
  • Transitional fossils (e.g., Archaeopteryx) show intermediate characteristics between ancestral and descendant groups, demonstrating evolutionary links [1 mark].
• Example for comparative anatomy:
  • Homologous structures (e.g., pentadactyl limb) have the same basic structural plan but different functions, indicating descent from a common ancestor [1 mark].
  • The similarities in bone arrangement cannot be explained by function alone and suggest shared ancestry [1 mark].
• (Accept any valid evidence with appropriate explanation. Award marks based on quality of explanation.)

Question 19 (4 marks)

(a) [1 mark]

• Allopatric speciation [1 mark].

(b) [3 marks]

• The two populations experience different environmental conditions/selection pressures in their respective lakes, leading to different adaptations [1 mark].
• Over time, genetic differences accumulate through natural selection and genetic drift. Mutations occurring in one population are not shared with the other [1 mark].
• Eventually, the populations become so genetically different that they can no longer interbreed to produce viable, fertile offspring (reproductive isolation). Even if the physical barrier is removed, gene flow cannot occur because they are now separate species [1 mark].

Question 20 (3 marks)

(a) [1 mark]

• Fitness refers to an organism's ability to survive and reproduce, passing its alleles to the next generation / reproductive success [1 mark].

(b) [2 marks]

• "Survival of the fittest" overemphasises survival alone, whereas evolutionary fitness depends on reproductive success—an organism that survives but does not reproduce has zero fitness [1 mark].
• The phrase also implies that evolution favours the "strongest" or most physically fit individuals, when in reality, fitness depends on how well an organism is adapted to its specific environment. Traits that enhance survival and reproduction in one environment may be disadvantageous in another [1 mark].

END OF ANSWER KEY