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A Level H2 Biology Evolution Diversity Quiz

Free A Level H2 Biology Evolution Diversity quiz, Gemma31B Exam version, with questions, answers, and A Level-style practice for Singapore students.

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A Level H2 Biology From Real Exams Generated by Gemma 4 31B Updated 2026-08-17

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Questions

A-Level Biology H2 Quiz - Evolution Diversity

Name: ____________________ Class: ____________________ Date: ____________________ Score: ________ / 55

Duration: 60 Minutes
Total Marks: 55
Instructions: Answer all questions. For structured questions, ensure your explanations are precise and use scientific terminology. Refer to the provided figures where applicable.

Section A: Short Answer & Knowledge (Questions 1-7)

Define the term species according to the biological species concept. [1]
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State two pieces of evidence from the fossil record that support the theory of evolution. [2]
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Explain why the presence of homologous structures in different species suggests a common ancestry. [2]
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Distinguish between allopatric speciation and sympatric speciation. [2]
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In the context of natural selection, explain the role of genetic variation within a population. [2]
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Describe how a "bottleneck effect" can lead to a decrease in the genetic diversity of a population. [2]
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State the difference between divergent evolution and convergent evolution. [2]
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Section B: Structured Response & Data Interpretation (Questions 8-15)

Fig 1 shows the amino acid sequences of a specific protein in four different species:
- Species A: Met-Gly-Ser-Leu-Val-Ala
- Species B: Met-Gly-Ser-Leu-Val-Gly
- Species C: Met-Ala-Ser-Phe-Val-Ala
- Species D: Met-Gly-Thr-Leu-Val-Ala
(a) Based on the sequences, which two species are most closely related? [1] \

(b) Explain how DNA sequence analysis is generally more reliable than morphological comparison for determining evolutionary relationships. [2]
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A population of insects is exposed to a new pesticide. Over several generations, the percentage of insects resistant to the pesticide increases from 2% to 75%. (a) Describe the process of natural selection that led to this change. [3]
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(b) Suggest why the pesticide-resistant allele may have been present in the population before the pesticide was introduced. [1]
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Fig 2 represents a phylogenetic tree of three mammals: a bat, a whale, and a dog. The bat and whale share a more recent common ancestor with each other than either does with the dog. (a) Explain how this tree reflects the concept of common descent. [2]
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(b) If a new trait is discovered that is shared only by the bat and the whale, would this be considered a synapomorphy or a homoplasy? Justify your answer. [2]
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Discuss how the evolution of the HIV virus makes it difficult to develop an effective vaccine. [3]
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Explain how polyploidy can lead to rapid speciation in plants. [3]
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A researcher compares the cytochrome c sequences of a human, a chimpanzee, and a yeast cell. (a) Predict which pair will show the highest percentage of sequence identity. [1] \

(b) Explain why cytochrome c is an ideal protein for comparing distantly related species. [2]
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Describe the role of reproductive isolation in the process of speciation. [3]
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Contrast the evolutionary significance of analogous structures versus homologous structures. [2]
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Section C: Extended Response & Synthesis (Questions 16-20)

With reference to the concept of adaptive radiation, explain how a single ancestral species could give rise to multiple species with diverse morphologies in an island archipelago. [4]
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Explain how the use of antibiotics in medicine provides a real-world example of directional selection. [3]
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Fig 3 shows a graph of the distribution of beak depths in a bird population before and after a severe drought. The mean beak depth increased significantly. (a) Explain the shift in the distribution curve. [3]
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(b) Predict the effect on the population if the environment shifted back to a state where only small seeds were available. [2]
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Discuss the evidence provided by comparative anatomy and molecular biology in supporting the theory that all living organisms share a universal common ancestor. [4]
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Evaluate the statement: "Evolution is a random process." Use your knowledge of mutation and natural selection to support your argument. [4]
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Answers

Answer Key - A-Level Biology H2 Quiz: Evolution Diversity

1. A group of organisms that can interbreed to produce fertile offspring. [1]

2. (Any two) Presence of transitional fossils; progression from simple to complex organisms in sedimentary layers; shared anatomical features across different strata. [2]

3. Homologous structures share a similar basic anatomy/origin but may have different functions; this indicates they were inherited from a common ancestor and modified over time via divergent evolution. [2]

4. Allopatric: Speciation occurs due to geographic isolation (physical barrier). Sympatric: Speciation occurs within the same geographic area (e.g., via polyploidy or behavioral changes). [2]

5. Genetic variation provides the raw material for natural selection; individuals with traits better suited to the environment are more likely to survive and reproduce, passing those alleles to the next generation. [2]

6. A drastic reduction in population size (due to disaster/hunting) randomly eliminates many alleles; the surviving small population has a reduced gene pool, leading to lower genetic diversity. [2]

7. Divergent: Related species evolve different traits due to different selection pressures. Convergent: Unrelated species evolve similar traits (analogous) due to similar selection pressures. [2]

8. (a) Species A and D (only one amino acid difference). [1] (b) DNA sequences provide a larger dataset (nucleotides vs amino acids); they account for silent mutations (synonymous codons) which are not visible in protein sequences. [2]

9. (a) Variation existed in the population (some had resistance alleles). Pesticide acted as a selection pressure. Resistant individuals survived and reproduced more successfully. Frequency of resistance allele increased in the gene pool. [3] (b) Mutation occurred randomly/spontaneously before the pesticide was introduced. [1]

10. (a) The branching pattern shows that all three mammals share a common ancestor; the closer the node, the more recent the common ancestor. [2] (b) Synapomorphy. It is a shared derived character that defines a clade (bat and whale), indicating it evolved in their most recent common ancestor. [2]

11. HIV has a high mutation rate (due to error-prone reverse transcriptase). This leads to high antigenic variation; the virus changes its surface proteins, meaning antibodies from a vaccine no longer recognize the mutated strains. [3]

12. Polyploidy (e.g., non-disjunction) results in offspring with extra sets of chromosomes. These offspring are often unable to interbreed with the diploid parent population (reproductive isolation), creating a new species in a single generation. [3]

13. (a) Human and Chimpanzee. [1] (b) Cytochrome c is found in almost all aerobic organisms (highly conserved); it performs a fundamental role in the electron transport chain, meaning it evolves very slowly. [2]

14. Reproductive isolation prevents gene flow between populations. This allows different mutations to accumulate and different selection pressures to act on each group independently, eventually leading to genetic divergence and speciation. [3]

15. Analogous structures show convergent evolution (similar function, different origin); Homologous structures show divergent evolution (similar origin, different function). [2]

16. Ancestral species colonizes various niches in the archipelago. Different environments (food sources, predators) exert different selection pressures. Populations adapt to specific niches (natural selection). Over time, reproductive isolation occurs, leading to multiple species from one ancestor. [4]

17. Antibiotics kill susceptible bacteria. Bacteria with resistance mutations survive. These survivors reproduce, shifting the population's trait distribution toward resistance. This is directional selection as the phenotype shifts in one specific direction. [3]

18. (a) Drought reduced small seeds; only large, hard seeds remained. Birds with deeper beaks could crack these seeds and survive. They reproduced more, increasing the frequency of "deep beak" alleles. [3] (b) Selection pressure would reverse; birds with smaller beaks would have a competitive advantage, and the mean beak depth would decrease over generations. [2]

19. Anatomy: Pentadactyl limb/homologous structures show shared blueprints. Molecular: Universal genetic code (DNA/RNA) and highly conserved proteins (Cytochrome c/Hemoglobin) prove a common biochemical origin for all life. [4]

20. Mutation is random (occurs without regard to the organism's needs). However, natural selection is NOT random; it specifically preserves traits that provide a survival/reproductive advantage. Therefore, evolution is a combination of random variation and non-random selection. [4]