Secondary 3 Biology Evolution Diversity Quiz

Secondary 3 Biology Quiz - Evolution Diversity: ANSWER KEY

Total Marks: 40

Section A: Multiple Choice (5 marks)

1. C) They have a high degree of similarity in their DNA sequences. [1 mark] Marking note: DNA similarity is the most direct and reliable molecular evidence for common ancestry. Accept C only.

2. B) They evolved independently as adaptations for flight. [1 mark] Marking note: Analogous structures arise from convergent evolution, not common ancestry. Accept B only.

3. C) Natural selection [1 mark] Marking note: The scenario describes differential survival based on heritable variation in shell colour due to predation pressure. Accept C only.

4. B) Individuals with traits better suited to their environment are more likely to survive and reproduce. [1 mark] Marking note: This is the core definition of natural selection. Accept B only.

5. C) A vestigial structure [1 mark] Marking note: A vestigial structure is a remnant of an organ that had a function in an ancestor but is reduced or functionless in the current organism. Accept C only.

Section B: Structured Questions (25 marks)

6. (a) Homologous structures. [1 mark] Accept: Structures that share a common basic plan/ancestry.

(b) Award up to 2 marks for:

• The forelimbs have a similar basic bone arrangement/pentadactyl limb structure [1 mark]
• This suggests they evolved from a common ancestor that possessed this basic limb structure [1 mark] Accept: The similarity in structure indicates divergent evolution from a common ancestor; the differences are due to adaptation to different functions/environments.

(c) Award 1 mark for:

• They are adapted for different functions (e.g., grasping in humans, swimming in whales, flying in bats, running in cats) / They live in different environments and have different modes of locomotion. Accept any reasonable explanation linking different functions/environments to different shapes.

7. (a) Award up to 2 marks for:

• Tree trunks were light-coloured/covered with lichen before the Industrial Revolution [1 mark]
• Light-coloured moths were camouflaged against the light tree trunks, making them less visible to predators (birds) [1 mark] Accept: Light moths had higher survival rate because they were better camouflaged.

(b) Award up to 3 marks for:

• Variation existed in the moth population (light and dark forms) [1 mark]
• When tree trunks became darkened by soot, dark moths were better camouflaged and less likely to be eaten by birds / light moths were more visible and more likely to be eaten [1 mark]
• Dark moths survived to reproduce and pass on their alleles/genes for dark colour to offspring; over generations, the proportion of dark moths increased [1 mark] Accept any clear description of the natural selection process: variation → selection pressure → differential survival → reproduction → change in population.

(c) Award 1 mark for:

• Mutation / random change in DNA/gene. Accept: Genetic mutation in the gene controlling wing colour.

8. (a) Award up to 2 marks for:

• Species A and B are most closely related [1 mark]
• They have the lowest percentage difference in DNA (2.5%), indicating the most recent common ancestor [1 mark] Accept: The smaller the DNA difference, the more closely related the species.

(b) Award up to 3 marks for:

• Correct branching order showing A and B as sister groups (branching from the most recent common ancestor) [1 mark]
• C branching off next (sharing a more distant common ancestor with A and B) [1 mark]
• D branching off first (sharing the most distant common ancestor with the other three) [1 mark]

Example acceptable cladogram:

    ┌─── A
  ┌─┤
  │ └─── B
──┤
  │ ┌─── C
  └─┤
    └─── D

Marking note: The order of branching must reflect the DNA difference data. A and B must be closest; D must be the outgroup (most distant). Award marks for correct topology, not artistic quality.

(c) Award up to 2 marks for:

• DNA sequences provide a direct record of evolutionary changes/mutations over time [1 mark]
• Physical characteristics can be influenced by environmental factors/convergent evolution, which may lead to misleading similarities (analogous structures) / DNA is less subject to convergent evolution [1 mark] Accept: DNA analysis is more objective and quantifiable; physical traits can be similar due to similar environments rather than common ancestry.

9. (a) Award up to 3 marks for:

• Genetic variation exists in the bacterial population; some bacteria possess alleles/genes that confer resistance to the antibiotic [1 mark]
• When the antibiotic is applied, it acts as a selection pressure: non-resistant bacteria are killed, while resistant bacteria survive [1 mark]
• Resistant bacteria reproduce and pass on the resistance alleles to their offspring; over generations, the proportion of resistant bacteria in the population increases [1 mark] Accept any clear natural selection explanation applied to antibiotic resistance.

(b) Award up to 2 marks for:

• Stopping early may leave some bacteria alive (especially those with partial resistance) [1 mark]
• These surviving bacteria can reproduce and the infection may return, and the bacteria may be more resistant to the antibiotic in future [1 mark] Accept: Completing the course ensures all bacteria are killed, reducing the chance of resistance developing.

10. (a) Award up to 3 marks for:

• The ancestral finch population showed variation in beak size and shape [1 mark]
• On different islands, different food sources were available; finches with beak shapes best suited to the available food had higher survival and reproductive success [1 mark]
• Over many generations, natural selection led to the divergence of the population into different species with distinct beak shapes adapted to specific food sources (adaptive radiation) [1 mark] Accept: Geographic isolation of populations on different islands, followed by natural selection acting on beak variation in response to different food sources.

Section C: Data-Based Question (10 marks)

11. (a) Award up to 2 marks for:

• The distribution shifted to the right / towards deeper beaks [1 mark]
• The mean/peak beak depth increased from approximately 9.5 mm to 10.5 mm / fewer birds with shallow beaks (below 9.0 mm) survived [1 mark] Accept any accurate description of the shift in the histogram.

(b) Award up to 3 marks for:

• The drought caused a shortage of small seeds; only large, hard seeds were available [1 mark]
• Finches with deeper beaks could crack open the large, hard seeds and obtain food [1 mark]
• Finches with shallower beaks could not feed effectively and died; deeper-beaked finches survived and reproduced, passing on their alleles for deep beaks [1 mark] Accept: The drought changed the food availability, favouring finches with deep beaks (directional selection).

(c) Award up to 3 marks for:

• The beak depth distribution would likely shift back towards shallower beaks / the mean beak depth would decrease [1 mark]
• An abundance of small, soft seeds would favour finches with smaller/shallower beaks, as they may be more efficient at handling small seeds [1 mark]
• Finches with smaller beaks would have higher survival and reproductive success, increasing the frequency of alleles for smaller beaks in the population [1 mark] Accept any reasonable prediction with explanation based on natural selection principles. Award marks for linking the change in food availability to a change in selection pressure and predicted evolutionary response.

(d) Award up to 2 marks for:

• There was variation in beak depth in the population; some individuals had deep enough beaks to survive [1 mark]
• These survivors reproduced and maintained the population / the population had sufficient genetic diversity to allow some individuals to survive the changed conditions [1 mark] Accept: Not all finches died; the survivors passed on their genes for deeper beaks, allowing the population to recover.

Section D: Application and Analysis (10 marks)

12. Award up to 3 marks for:

• Natural selection is the process whereby organisms better adapted to their environment tend to survive and produce more offspring [1 mark]
• Condition 1: There must be variation in traits within a population [1 mark]
• Condition 2: The variation must be heritable / There must be differential survival and reproduction based on the traits / There must be a selection pressure [1 mark] Accept any two valid conditions. Award marks for accurate definition and conditions.

13. Award up to 2 marks for:

• The fossil record shows a chronological sequence of organisms, with simpler forms in older rocks and more complex forms in younger rocks [1 mark]
• It shows transitional forms/intermediate species that link different groups, indicating gradual change over time [1 mark] Accept: Fossils show that organisms have changed over time; extinct species are found that are different from modern species.

14. Award up to 2 marks for:

• Low genetic variation means the population has less ability to adapt to environmental changes/new diseases [1 mark]
• If a new disease or environmental change occurs, there may be few or no individuals with resistant/adaptive alleles, leading to possible extinction [1 mark] Accept: Reduced evolutionary potential; inbreeding depression; accumulation of harmful recessive alleles.

15. Award up to 3 marks for:

• Variation existed in the insect population; some insects possessed alleles/genes that conferred resistance to the pesticide [1 mark]
• When the pesticide was applied, it killed susceptible insects, but resistant insects survived (selection pressure) [1 mark]
• Resistant insects reproduced and passed on resistance alleles to offspring; over generations, the frequency of resistance alleles increased, making the pesticide less effective [1 mark] Accept any clear natural selection explanation applied to pesticide resistance.

16. Award up to 2 marks for:

• Homologous structures share a common ancestral origin but may have different functions (e.g., forelimbs of vertebrates) [1 mark]
• Analogous structures have similar functions but different ancestral origins/evolved independently (e.g., wings of birds and insects) [1 mark] Accept any valid examples. Award 1 mark for each correct distinction with example.

17. Award up to 2 marks for:

• Humans and chimpanzees share a common ancestor; they did not evolve directly from one another [1 mark]
• Both lineages evolved separately from that common ancestor millions of years ago [1 mark] Accept: The evolutionary relationship is like a branching tree, not a linear chain.

18. Award up to 3 marks for:

• A population becomes separated by a geographic barrier (e.g., mountain, river, ocean) [1 mark]
• The separated populations experience different environmental conditions/selection pressures and accumulate different mutations [1 mark]
• Over many generations, the populations diverge genetically to the point where they can no longer interbreed to produce fertile offspring, forming new species [1 mark] Accept any clear description of allopatric speciation.

19. Award up to 2 marks for:

• Homologous structures share a common ancestral origin but have evolved different shapes and functions due to adaptation to different environments/ways of life [1 mark]
• The penguin wing adapted for swimming in water, while the eagle wing adapted for flying in air; both evolved from the forelimb of a common ancestor [1 mark] Accept: Divergent evolution leads to homologous structures with different functions.

20. Award up to 2 marks for:

• Compare DNA sequences / genetic analysis of the island lizard and mainland lizards [1 mark]
• Compare physical characteristics/morphology / Compare anatomical structures / Look for homologous structures [1 mark] Accept: Any two valid types of evidence (molecular, morphological, fossil, embryological). Award 1 mark per suggestion.