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O Level Biology Evolution Diversity Quiz
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Questions
O-Level Biology Quiz - Evolution Diversity
Name: _________________________ Class: _________________________ Date: _________________________ Score: ______ / 40
Duration: 45 minutes Total Marks: 40
Instructions:
- Answer ALL questions in the spaces provided.
- The number of marks for each question is shown in brackets [ ].
- Marks are awarded for correct biological terminology and clear explanations.
- Read each question carefully before answering.
Section A: Short Answer (10 marks)
Answer questions 1–5 in this section.
1. Define the term natural selection. [2]
2. State two sources of genetic variation within a population. [2]
3. Explain why bacteria can evolve resistance to antibiotics rapidly. [2]
4. Distinguish between continuous variation and discontinuous variation. Give one example of each. [4]
5. What is meant by the term species? [2]
Section B: Structured Response (18 marks)
Answer questions 6–10 in this section.
6. The peppered moth (Biston betularia) exists in two forms: a pale, speckled form and a dark, melanic form. Before the Industrial Revolution in England, the pale form was more common. During the Industrial Revolution, when tree trunks became darkened by soot, the dark form became more common.
(a) Explain why the pale form was more common before the Industrial Revolution. [2]
(b) Explain why the dark form became more common during the Industrial Revolution. [3]
(c) After clean air legislation was introduced, lichens grew back on tree trunks and the pale form increased in frequency again. What does this demonstrate about natural selection? [1]
7. The diagram below shows the forelimb bones of four different vertebrates: a human, a whale, a bat, and a bird. Despite their different functions, the basic bone structure is similar.
(a) What term describes structures that have a similar basic plan but different functions? [1]
(b) Explain how these structures provide evidence for evolution from a common ancestor. [3]
(c) The wings of a bat and the wings of an insect both enable flight but have very different structures. What term describes such structures, and what type of evolution produces them? [2]
8. A population of rabbits lives in a cold environment. Over many generations, the rabbits develop thicker fur.
(a) Using the theory of natural selection, explain how thicker fur evolved in this rabbit population. [4]
(b) Suggest one selective pressure, other than temperature, that could drive evolution in a rabbit population. [1]
(c) Explain why evolution by natural selection cannot occur if there is no variation in the population. [1]
9. Explain how the fossil record provides evidence for evolution. [3]
10. Explain why the development of antibiotic resistance in bacteria is considered an example of evolution by natural selection. [3]
Section C: Data Interpretation and Application (12 marks)
Answer questions 11–15 in this section.
11. A scientist studied beak depth in a population of finches on an island. During a drought, only large, hard seeds were available. The graph below shows the distribution of beak depth before and after the drought.
Distribution of Beak Depth in a Finch Population
| Beak depth (mm) | Number of finches before drought | Number of finches after drought |
|---|---|---|
| 6.0 – 6.9 | 5 | 1 |
| 7.0 – 7.9 | 12 | 3 |
| 8.0 – 8.9 | 25 | 8 |
| 9.0 – 9.9 | 30 | 15 |
| 10.0 – 10.9 | 20 | 28 |
| 11.0 – 11.9 | 6 | 22 |
| 12.0 – 12.9 | 2 | 13 |
(a) Describe the change in the distribution of beak depth after the drought. [2]
(b) Explain why finches with larger beaks were more likely to survive the drought. [2]
(c) Predict the likely distribution of beak depth in the next generation of finches born after the drought. Explain your prediction. [3]
(d) If the drought ended and small, soft seeds became abundant again, predict what would happen to beak depth over many generations. Explain your answer. [3]
12. The graph below shows the development of antibiotic resistance in a population of bacteria over time, after the introduction of an antibiotic.
Percentage of Antibiotic-Resistant Bacteria Over Time
| Time (months) | Resistant bacteria (%) |
|---|---|
| 0 | 2 |
| 3 | 5 |
| 6 | 15 |
| 9 | 38 |
| 12 | 65 |
| 15 | 82 |
| 18 | 91 |
(a) Describe the trend shown in the data. [1]
(b) Explain why the percentage of resistant bacteria increased over time. [3]
(c) Suggest and explain one measure that could slow down the development of antibiotic resistance. [2]
13. Explain how comparative embryology provides evidence for evolution. [2]
14. Explain how artificial selection differs from natural selection. [2]
15. Explain how geographical isolation can lead to the formation of a new species. [3]
Section D: Extended Response (10 marks)
Answer questions 16–20 in this section.
16. Discuss how the overuse of antibiotics in agriculture and medicine has contributed to the rise of antibiotic-resistant bacteria. [4]
17. Explain how DNA sequencing and molecular biology provide evidence for evolution. [3]
18. Explain how the pentadactyl limb structure in different vertebrates supports the theory of evolution. [3]
19. Explain how natural selection can lead to the formation of a new species. [4]
20. Discuss the importance of genetic variation for the survival of a species in a changing environment. [4]
END OF QUIZ
Check your answers carefully before submitting.
Answers
O-Level Biology Quiz - Evolution Diversity — Answer Key
Total Marks: 40
Section A: Short Answer (10 marks)
1. Define the term natural selection. [2]
- Answer: Natural selection is the process by which organisms with advantageous traits/characteristics that are better suited to their environment are more likely to survive and reproduce [1], passing these favourable traits to their offspring, leading to gradual change in the population over generations [1].
- Marking notes: Award [1] for "differential survival and reproduction" concept; [1] for "passing traits to offspring" or "change over generations". Accept "survival of the fittest" only if explained.
2. State two sources of genetic variation within a population. [2]
- Answer:
- Mutation (changes in DNA/gene sequence) [1]
- Sexual reproduction / meiosis / crossing over / independent assortment / random fertilisation [1]
- Marking notes: Award [1] for each correct source. Accept any valid source of genetic variation. Do not accept "environmental factors" alone as these do not cause genetic variation.
3. Explain why bacteria can evolve resistance to antibiotics rapidly. [2]
- Answer: Bacteria reproduce very rapidly / have a short generation time, so mutations can spread quickly through the population [1]. Bacteria have a large population size, increasing the chance of resistant mutants appearing, and can transfer resistance genes horizontally via plasmids [1].
- Marking notes: Award [1] for rapid reproduction/short generation time; [1] for large population size OR horizontal gene transfer/plasmids.
4. Distinguish between continuous variation and discontinuous variation. Give one example of each. [4]
- Answer:
- Continuous variation: traits that show a range of phenotypes with no distinct categories; influenced by many genes (polygenic) and environment; individuals cannot be placed into discrete groups [1]. Example: height in humans / body mass / skin colour [1].
- Discontinuous variation: traits that fall into distinct, separate categories with no intermediates; usually controlled by a single gene; environment has little effect [1]. Example: ABO blood groups / tongue rolling / attached vs free earlobes [1].
- Marking notes: Award [1] for each correct description and [1] for each correct example. Accept any valid examples.
5. What is meant by the term species? [2]
- Answer: A species is a group of organisms that can interbreed / reproduce naturally to produce fertile offspring [1] and are reproductively isolated from other such groups [1].
- Marking notes: Award [1] for "interbreed and produce fertile offspring"; [1] for "reproductively isolated". Accept equivalent phrasing.
Section B: Structured Response (18 marks)
6. Peppered moth question.
(a) Explain why the pale form was more common before the Industrial Revolution. [2]
- Answer: Before the Industrial Revolution, tree trunks were covered with pale lichens [1]. The pale, speckled moths were camouflaged against the lichen-covered tree trunks, so they were less likely to be seen and eaten by predators (birds). The dark form was more visible and more likely to be preyed upon [1].
- Marking notes: Award [1] for camouflage of pale form on lichen-covered trees; [1] for differential predation (pale survive, dark eaten).
(b) Explain why the dark form became more common during the Industrial Revolution. [3]
- Answer: During the Industrial Revolution, soot from factories killed lichens and darkened tree trunks [1]. The dark (melanic) form was now better camouflaged against the darkened tree trunks, while the pale form became more visible to predators [1]. Dark moths survived and reproduced more, passing the dark-colour allele to their offspring. Over generations, the frequency of the dark form increased in the population [1].
- Marking notes: Award [1] for environmental change (soot darkening trees); [1] for differential survival (dark camouflaged, pale visible); [1] for reproduction and inheritance leading to increased frequency.
(c) After clean air legislation was introduced, lichens grew back on tree trunks and the pale form increased in frequency again. What does this demonstrate about natural selection? [1]
- Answer: Natural selection depends on environmental conditions / the selective advantage of a trait depends on the environment / what is advantageous in one environment may not be advantageous in another [1].
- Marking notes: Accept any answer that links natural selection to changing environmental conditions.
7. Vertebrate forelimb question.
(a) What term describes structures that have a similar basic plan but different functions? [1]
- Answer: Homologous structures / homology [1].
(b) Explain how these structures provide evidence for evolution from a common ancestor. [3]
- Answer: The forelimbs of these vertebrates share the same basic bone structure (pentadactyl limb), despite being used for different functions (grasping, swimming, flying, walking) [1]. This similarity in basic structure suggests they were inherited from a common ancestor that possessed this limb structure [1]. The differences in shape and function arose through adaptive radiation / divergent evolution as each lineage adapted to different environments and ways of life [1].
- Marking notes: Award [1] for identifying the shared basic structure; [1] for linking to common ancestry; [1] for explaining divergence/adaptation to different functions.
(c) The wings of a bat and the wings of an insect both enable flight but have very different structures. What term describes such structures, and what type of evolution produces them? [2]
- Answer: Analogous structures [1]. Convergent evolution [1].
- Marking notes: Award [1] for each correct term. Must have both for full marks.
8. Rabbit fur thickness question.
(a) Using the theory of natural selection, explain how thicker fur evolved in this rabbit population. [4]
- Answer: Within the rabbit population, there was genetic variation in fur thickness; some rabbits naturally had thicker fur than others [1]. In the cold environment, rabbits with thicker fur were better insulated and lost less body heat, so they were more likely to survive the cold [1]. These rabbits survived and reproduced more successfully, passing the alleles for thick fur to their offspring [1]. Over many generations, the frequency of the thick-fur allele increased in the population, resulting in the evolution of thicker fur [1].
- Marking notes: Award [1] for variation; [1] for differential survival (selective advantage); [1] for reproduction and inheritance; [1] for change in allele frequency over generations.
(b) Suggest one selective pressure, other than temperature, that could drive evolution in a rabbit population. [1]
- Answer: Predation (e.g., coat colour for camouflage) / food availability (e.g., digestive efficiency) / disease resistance / competition for mates (sexual selection) [1].
- Marking notes: Accept any valid selective pressure with brief explanation.
(c) Explain why evolution by natural selection cannot occur if there is no variation in the population. [1]
- Answer: Without variation, all individuals are identical, so there is no differential survival or reproduction based on traits / natural selection has nothing to act upon / all individuals have equal fitness [1].
- Marking notes: Accept any answer that explains the necessity of variation for selection to operate.
9. Explain how the fossil record provides evidence for evolution. [3]
- Answer: Fossils show that organisms that lived in the past were different from organisms alive today, indicating that life forms have changed over time [1]. The sequence of fossils in rock layers shows a gradual progression from simpler to more complex organisms [1]. Transitional fossils (e.g., Archaeopteryx) show intermediate characteristics between different groups, providing evidence for common ancestry [1].
- Marking notes: Award [1] for change over time; [1] for progression from simple to complex; [1] for transitional fossils/common ancestry.
10. Explain why the development of antibiotic resistance in bacteria is considered an example of evolution by natural selection. [3]
- Answer: Within a bacterial population, there is genetic variation; some bacteria possess alleles that confer resistance to an antibiotic [1]. When the antibiotic is applied, it acts as a selective agent, killing susceptible bacteria while resistant bacteria survive [1]. The resistant bacteria reproduce and pass the resistance alleles to their offspring, increasing the frequency of resistance in the population over generations [1].
- Marking notes: Award [1] for variation; [1] for differential survival; [1] for inheritance and change in allele frequency.
Section C: Data Interpretation and Application (12 marks)
11. Finch beak depth question.
(a) Describe the change in the distribution of beak depth after the drought. [2]
- Answer: The distribution shifted towards larger beak depths / the mean/median beak depth increased [1]. The number of finches with smaller beaks (6.0–9.9 mm) decreased, while the number with larger beaks (10.0–12.9 mm) increased [1].
- Marking notes: Award [1] for identifying the directional shift; [1] for referencing specific data or describing the decrease in small beaks and increase in large beaks.
(b) Explain why finches with larger beaks were more likely to survive the drought. [2]
- Answer: During the drought, only large, hard seeds were available as a food source [1]. Finches with larger beaks were better able to crack open and eat these hard seeds, so they obtained more food and were more likely to survive, while finches with smaller beaks could not feed effectively and died [1].
- Marking notes: Award [1] for linking large beaks to ability to eat hard seeds; [1] for differential survival.
(c) Predict the likely distribution of beak depth in the next generation of finches born after the drought. Explain your prediction. [3]
- Answer: The next generation will have a distribution shifted towards larger beak depths, similar to the post-drought distribution [1]. This is because the surviving finches with larger beaks will reproduce and pass on their alleles for larger beak depth to their offspring [1]. Since beak depth is a heritable trait, the offspring will tend to have beak depths similar to their parents, maintaining the shift towards larger beaks [1].
- Marking notes: Award [1] for predicting a shift towards larger beaks; [1] for inheritance of alleles; [1] for linking to heritability of the trait.
(d) If the drought ended and small, soft seeds became abundant again, predict what would happen to beak depth over many generations. Explain your answer. [3]
- Answer: The distribution of beak depth would likely shift back towards smaller beaks [1]. With small, soft seeds abundant, finches with smaller beaks would be able to feed efficiently, while larger beaks might be less efficient for handling small seeds [1]. Finches with smaller beaks would have a selective advantage, survive better, and reproduce more, passing on alleles for smaller beaks. Over many generations, the frequency of smaller beaks would increase [1].
- Marking notes: Award [1] for predicting a shift towards smaller beaks; [1] for explaining the change in selective pressure; [1] for linking to differential survival, reproduction, and change in allele frequency.
12. Antibiotic resistance data question.
(a) Describe the trend shown in the data. [1]
- Answer: The percentage of antibiotic-resistant bacteria increased over time / from 2% at 0 months to 91% at 18 months [1].
- Marking notes: Award [1] for stating the increasing trend. Accept reference to specific data points.
(b) Explain why the percentage of resistant bacteria increased over time. [3]
- Answer: Initially, a small proportion of bacteria possessed alleles for antibiotic resistance due to mutation [1]. When the antibiotic was introduced, it killed the susceptible bacteria, while the resistant bacteria survived (differential survival) [1]. The resistant bacteria reproduced, passing the resistance alleles to their offspring. With each generation, the proportion of resistant bacteria increased, as susceptible bacteria were continually eliminated by the antibiotic [1].
- Marking notes: Award [1] for pre-existing variation/mutation; [1] for differential survival; [1] for reproduction and inheritance leading to increased proportion.
(c) Suggest and explain one measure that could slow down the development of antibiotic resistance. [2]
- Answer: Complete the full course of antibiotics [1]. This ensures all bacteria are killed, reducing the chance that partially resistant bacteria survive and reproduce [1]. OR: Use antibiotics only when necessary / avoid over-prescription [1] to reduce the selective pressure on bacterial populations [1]. OR: Use a combination of antibiotics [1] so that bacteria resistant to one antibiotic are killed by the other [1].
- Marking notes: Award [1] for a valid measure; [1] for a correct explanation linked to reducing selection or survival of resistant bacteria.
13. Explain how comparative embryology provides evidence for evolution. [2]
- Answer: Embryos of different vertebrates show striking similarities in early stages of development (e.g., pharyngeal pouches, tail) [1]. These similarities suggest that these organisms share a common ancestor and have inherited similar developmental pathways [1].
- Marking notes: Award [1] for identifying embryonic similarities; [1] for linking to common ancestry.
14. Explain how artificial selection differs from natural selection. [2]
- Answer: In artificial selection, humans select which organisms reproduce based on desired traits [1], whereas in natural selection, the environment determines which organisms survive and reproduce based on advantageous traits [1].
- Marking notes: Award [1] for human choice in artificial selection; [1] for environmental factors in natural selection.
15. Explain how geographical isolation can lead to the formation of a new species. [3]
- Answer: A population becomes separated by a geographical barrier (e.g., mountain, river, sea), preventing gene flow between the two groups [1]. The two populations experience different environmental conditions and selective pressures, leading to different adaptations through natural selection [1]. Over many generations, the populations become so genetically different that they can no longer interbreed to produce fertile offspring, resulting in the formation of a new species [1].
- Marking notes: Award [1] for geographical barrier and isolation; [1] for different selective pressures and adaptations; [1] for reproductive isolation and speciation.
Section D: Extended Response (10 marks)
16. Discuss how the overuse of antibiotics in agriculture and medicine has contributed to the rise of antibiotic-resistant bacteria. [4]
- Answer: Overuse of antibiotics creates a strong selective pressure favouring resistant bacteria [1]. In medicine, unnecessary prescriptions or patients not completing courses allow resistant bacteria to survive and multiply [1]. In agriculture, antibiotics are often used routinely in livestock to promote growth or prevent disease, exposing large bacterial populations to constant selection [1]. Resistant bacteria from livestock can transfer to humans through food, direct contact, or the environment, spreading resistance genes [1]. This widespread use accelerates the evolution and spread of antibiotic resistance globally.
- Marking notes: Award [1] for selective pressure concept; [1] for medical misuse; [1] for agricultural use; [1] for transmission between animals and humans.
17. Explain how DNA sequencing and molecular biology provide evidence for evolution. [3]
- Answer: DNA sequencing allows comparison of the genetic code of different species; closely related species have more similar DNA sequences than distantly related species [1]. This indicates that they share a more recent common ancestor [1]. Molecular biology also compares proteins (e.g., cytochrome c) and other molecules; similarities in these molecules across species further support evolutionary relationships [1].
- Marking notes: Award [1] for DNA sequence similarity; [1] for linking to common ancestry; [1] for mentioning proteins/molecular comparisons.
18. Explain how the pentadactyl limb structure in different vertebrates supports the theory of evolution. [3]
- Answer: The pentadactyl limb is a limb with five digits, found in the forelimbs of diverse vertebrates such as humans, whales, bats, and birds [1]. Despite being used for different functions (e.g., grasping, swimming, flying), the underlying bone structure is remarkably similar [1]. This similarity is best explained by these organisms having inherited the basic limb structure from a common ancestor, with modifications arising through natural selection for different functions (divergent evolution) [1].
- Marking notes: Award [1] for describing the pentadactyl limb; [1] for noting similar structure, different functions; [1] for common ancestry and divergent evolution.
19. Explain how natural selection can lead to the formation of a new species. [4]
- Answer: Within a population, there is genetic variation [1]. If a population becomes isolated (e.g., geographically), different selective pressures act on the separated groups [1]. Individuals with traits suited to their local environment survive and reproduce, leading to different adaptations in each population [1]. Over many generations, the accumulated genetic differences may become so great that individuals from the two populations can no longer interbreed to produce fertile offspring, resulting in reproductive isolation and the formation of a new species [1].
- Marking notes: Award [1] for variation; [1] for isolation and different selective pressures; [1] for differential survival and adaptation; [1] for reproductive isolation and speciation.
20. Discuss the importance of genetic variation for the survival of a species in a changing environment. [4]
- Answer: Genetic variation provides the raw material for natural selection; without it, a population cannot adapt to changes [1]. In a changing environment, some individuals may possess alleles that confer an advantage under the new conditions (e.g., resistance to a new disease, tolerance to higher temperatures) [1]. These individuals are more likely to survive and reproduce, passing the advantageous alleles to their offspring, allowing the population to evolve and persist [1]. A population with low genetic variation is vulnerable to extinction because if no individuals have the traits needed to survive the change, the entire population may die out [1].
- Marking notes: Award [1] for variation as raw material; [1] for advantageous alleles in new conditions; [1] for survival, reproduction, and adaptation; [1] for risk of extinction without variation.
END OF ANSWER KEY