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Secondary 4 Combined Science Biology Evolution Diversity Quiz
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Questions
Secondary 4 Combined Science Biology Quiz - Evolution Diversity
Name: ___________________________
Class: ___________________________
Date: ___________________________
Score: _________ / 40
Duration: 45 minutes
Total Marks: 40
Instructions:
- Answer all questions in the spaces provided.
- Write your answers clearly and in complete sentences where required.
- The number of marks for each question is shown in brackets [ ].
- Where diagrams are referenced, use the information given to support your answers.
- This quiz is based on the Evolution & Diversity topic within the O-Level Combined Science (Biology) syllabus.
- This content is syllabus-aligned practice material and is not derived from past-year exam papers.
Section A: Multiple Choice & Short Answer (Questions 1–10)
Questions 1–5: Choose the most accurate answer. Each question carries 1 mark.
1. Which of the following best describes evolution?
(a) A change in an individual organism's traits during its lifetime
(b) A change in the genetic composition of a population over successive generations
(c) The survival of the strongest organisms in a habitat
(d) The process by which organisms adapt to their environment within one generation
Answer: _________________________________ [1]
2. The primary source of new genetic variation in a population is:
(a) Natural selection
(b) Mutation
(c) Genetic drift
(d) Selective breeding
Answer: _________________________________ [1]
3. Which of the following is an example of natural selection?
(a) A farmer choosing the largest tomatoes to save seeds from
(b) Bacteria developing resistance to an antibiotic over many generations
(c) A plant growing taller because it receives more sunlight
(d) A dog learning to sit on command
Answer: _________________________________ [1]
4. The term "fitness" in an evolutionary context refers to an organism's:
(a) Physical strength and speed
(b) Ability to survive and reproduce in its environment
(c) Resistance to all diseases
(d) Size compared to other organisms in the population
Answer: _________________________________ [1]
5. Which type of evidence for evolution compares the DNA or protein sequences of different species?
(a) Fossil evidence
(b) Anatomical evidence
(c) Molecular evidence
(d) Embryological evidence
Answer: _________________________________ [1]
Questions 6–10: Short answer. Write your answer in the space provided.
6. Define the term gene pool. [2]
_______________________________________________________________ [2]
7. State two conditions that must be met for a population to be in Hardy-Weinberg equilibrium (i.e., for evolution not to occur). [2]
(a) _______________________________________________________________
(b) _______________________________________________________________ [2]
8. Distinguish between directional selection and stabilising selection. Give one example of each. [3]
Directional selection:
Example: _______________________________________________________________
Stabilising selection:
Example: _______________________________________________________________ [3]
9. The diagram below (described in text) shows the beak depths of a population of finches on an island before and after a drought. After the drought, the average beak depth increased. Explain this observation in terms of natural selection. [3]
_______________________________________________________________ [3]
10. Explain what is meant by speciation. State one factor that can lead to speciation. [2]
Speciation:
Factor: _______________________________________________________________ [2]
Section B: Structured Response (Questions 11–17)
11. A population of moths exists in two colour morphs: light and dark. Before industrialisation, the light morph was more common. After industrialisation darkened the tree trunks with soot, the dark morph became more common.
(a) Explain why the dark morph became more common after industrialisation. Use the concept of natural selection in your answer. [4]
_______________________________________________________________ [4]
(b) State what would likely happen to the proportion of dark moths if pollution were reduced and tree trunks became lighter again. Explain your reasoning. [2]
_______________________________________________________________ [2]
12. The table below shows the number of individuals with different genotypes in a population of flowers.
| Genotype | RR (red) | Rr (pink) | rr (white) |
|---|---|---|---|
| Number | 36 | 48 | 16 |
(a) Calculate the frequency of the recessive allele (r) in this population. Show your working. [3]
Working:
Answer: _________________________________ [3]
(b) State whether this population is in Hardy-Weinberg equilibrium. Explain your reasoning. [2]
_______________________________________________________________ [2]
13. Describe how the fossil record provides evidence for evolution. Include in your answer:
- What fossils are
- How the fossil record shows change over time
- One limitation of fossil evidence [4]
_______________________________________________________________ [4]
14. The forelimbs of a human, a bat, and a whale have similar bone structures despite being used for different functions.
(a) What term is used to describe structures like these? [1]
_______________________________________________________________ [1]
(b) What does this similarity suggest about the evolutionary relationship between these organisms? [2]
_______________________________________________________________ [2]
(c) Explain how such structures arise through evolution. [2]
_______________________________________________________________ [2]
15. Explain how geographic isolation can lead to the formation of new species. In your answer, describe the sequence of events from isolation to speciation. [5]
_______________________________________________________________ [5]
16. Antibiotic resistance in bacteria is an example of evolution by natural selection.
(a) Explain how antibiotic resistance develops in a bacterial population. [4]
_______________________________________________________________ [4]
(b) State two practices that can slow the development of antibiotic resistance. [2]
(i) _______________________________________________________________
(ii) _______________________________________________________________ [2]
17. The diagram (described in text) shows a phylogenetic tree of five species (A, B, C, D, E). Species A and B share a recent common ancestor. Species C diverged earlier. Species D and E share a recent common ancestor that is different from the ancestor of A and B.
(a) Which two species are most closely related? Explain how you determined this. [2]
_______________________________________________________________ [2]
(b) What does a node (branching point) on a phylogenetic tree represent? [1]
_______________________________________________________________ [1]
(c) State one type of data that scientists use to construct phylogenetic trees. [1]
_______________________________________________________________ [1]
Section C: Data-Based & Extended Response (Questions 18–20)
18. The graph below (described in text) shows the change in average body mass of a population of deer mice over 20 generations. The environment experienced increasingly cold temperatures over this period.
Graph description: The x-axis shows generation number (0 to 20). The y-axis shows average body mass in grams. The trend line shows a steady increase in average body mass from approximately 18 g at generation 0 to approximately 24 g at generation 20.
(a) Describe the trend shown in the graph. [2]
_______________________________________________________________ [2]
(b) Explain this trend using the theory of natural selection. [4]
_______________________________________________________________ [4]
(c) Predict what would happen to average body mass if the environment became significantly warmer over the next 20 generations. Explain your reasoning. [2]
_______________________________________________________________ [2]
19. Two populations of a species of grasshopper live on opposite sides of a newly formed canyon. Over thousands of years, the two populations evolve differences in mating calls and breeding seasons.
(a) Identify the type of reproductive isolation described in this scenario. [1]
_______________________________________________________________ [1]
(b) Explain how the canyon acts as a barrier to gene flow. [2]
_______________________________________________________________ [2]
(c) Describe the sequence of events that would lead to the two populations becoming separate species. [4]
_______________________________________________________________ [4]
(d) If the two populations were brought back into contact after many generations and could no longer interbreed successfully, what term describes this outcome? [1]
_______________________________________________________________ [1]
20. Read the following passage and answer the questions that follow.
The Galápagos Islands are home to several species of finches known as Darwin's finches. These species differ mainly in beak size and shape, which correspond to different food sources. Some species have large, strong beaks for cracking seeds, while others have thin, pointed beaks for catching insects. DNA analysis shows that all these species descended from a common ancestor that colonised the islands from the South American mainland millions of years ago.
(a) Explain how Darwin's finches provide evidence for evolution by natural selection. [4]
_______________________________________________________________ [4]
(b) Suggest why different islands in the Galápagos archipelago have finch species with different beak shapes. [3]
_______________________________________________________________ [3]
(c) What type of evolution is illustrated by the diversification of a single ancestral species into multiple species occupying different ecological niches? [1]
_______________________________________________________________ [1]
Answers
Secondary 4 Combined Science Biology Quiz - Evolution Diversity
Answer Key
Section A: Multiple Choice & Short Answer (Questions 1–10)
1. (b) A change in the genetic composition of a population over successive generations [1]
Note: Evolution occurs at the population level, not the individual level. Option (a) describes phenotypic plasticity, not evolution. Option (c) is an oversimplification (survival of the "fittest," not necessarily the "strongest"). Option (d) confuses adaptation within a lifetime with evolutionary change across generations.
2. (b) Mutation [1]
Note: Mutation is the ultimate source of new alleles. Natural selection, genetic drift, and selective breeding act on existing variation but do not create new genetic material.
3. (b) Bacteria developing resistance to an antibiotic over many generations [1]
Note: This is natural selection acting on pre-existing genetic variation in a bacterial population. Option (a) is artificial selection. Options (c) and (d) are not heritable changes.
4. (b) Ability to survive and reproduce in its environment [1]
Note: In evolutionary biology, "fitness" is defined reproductively, not physically.
5. (c) Molecular evidence [1]
Note: Molecular evidence compares DNA, RNA, or protein sequences to determine evolutionary relationships. Fossil evidence examines preserved remains; anatomical evidence compares body structures; embryological evidence compares developmental stages.
6. Definition of gene pool: [2]
The complete set of all alleles (or genes) present in a population of organisms at a given time. [2]
Marking: Award 1 mark for "all alleles/genes" and 1 mark for "in a population." Answers that say "all the genes in an organism" are incorrect — the gene pool refers to a population, not an individual.
7. Two conditions for Hardy-Weinberg equilibrium: [2]
(a) No mutation (or random mating / no natural selection / large population size / no migration — any valid condition) [1]
(b) A second valid condition different from (a) [1]
Acceptable answers include: no mutation, random mating, no natural selection, infinitely large population (no genetic drift), no gene flow (migration/emigration). Award 1 mark per valid condition, max 2.
8. Directional vs. stabilising selection: [3]
Directional selection: Selection that favours one extreme phenotype over the mean and other extreme, causing the population mean to shift in one direction over time. [1]
Example: Antibiotic resistance in bacteria — bacteria with greater resistance survive and reproduce, shifting the population toward higher resistance. (Accept any valid example.) [0.5]
Stabilising selection: Selection that favours the intermediate phenotype and acts against both extremes, reducing variation and maintaining the population mean. [1]
Example: Birth weight in humans — babies of intermediate weight have higher survival rates; very small or very large babies face higher risks. (Accept any valid example.) [0.5]
Marking: Award marks for correct definitions and valid examples. Examples need not be identical to those given above.
9. Finch beak depth after drought — natural selection explanation: [3]
- Before the drought, finches had a range of beak depths (variation existed in the population). [1]
- The drought reduced the availability of small, soft seeds, leaving mostly large, hard seeds. [1]
- Finches with deeper (stronger) beaks were better able to crack the hard seeds, so they survived and reproduced more successfully. They passed the genes for deeper beaks to offspring. Over generations, the average beak depth increased. [1]
Marking: Award 1 mark each for (i) recognition of pre-existing variation, (ii) identification of the selective pressure, and (iii) explanation of differential survival/reproduction leading to change in the population.
10. Speciation: [2]
Speciation: The evolutionary process by which populations evolve to become distinct (separate) species. [1]
Factor: Geographic isolation / reproductive isolation / genetic mutation / natural selection in different environments (accept any valid factor). [1]
Marking: Award 1 mark for a correct definition (must include the idea of new species forming from existing ones). Award 1 mark for any valid factor.
Section B: Structured Response (Questions 11–17)
11. Peppered moth scenario:
(a) [4]
- Before industrialisation, light-coloured moths were better camouflaged against light-coloured (lichen-covered) tree trunks, so they were less likely to be eaten by predators. [1]
- After industrialisation, soot darkened the tree trunks. Dark-coloured moths were now better camouflaged and less likely to be preyed upon. [1]
- Dark-coloured moths therefore had a higher chance of surviving and reproducing. [1]
- They passed the allele for dark coloration to their offspring. Over many generations, the frequency of the dark allele increased, and the dark morph became more common in the population. [1]
Marking: Award 1 mark for each of the four points above. Answers must reference natural selection (differential survival/reproduction due to camouflage/predation).
(b) [2]
The proportion of dark moths would likely decrease. [1]
As tree trunks become lighter again, light-coloured moths would regain their camouflage advantage and be less preyed upon, so they would survive and reproduce more successfully, increasing in frequency over generations. [1]
Marking: Award 1 mark for the correct prediction and 1 mark for a valid explanation linked to natural selection.
12. Flower genotype frequency calculation:
(a) Allele frequency calculation: [3]
Total individuals = 36 + 48 + 16 = 100
Total alleles = 100 × 2 = 200
Number of r alleles = (48 × 1) + (16 × 2) = 48 + 32 = 80
Frequency of r = 80 / 200 = 0.4 (or 40%) [3]
Marking: Award 1 mark for correct total number of alleles, 1 mark for correct count of r alleles, 1 mark for correct final answer. Accept 0.4 or 40% or 2/5.
(b) Hardy-Weinberg equilibrium check: [2]
Expected genotype frequencies if in H-W equilibrium:
p² = (frequency of R)² = (0.6)² = 0.36 → Expected RR = 36
2pq = 2(0.6)(0.4) = 0.48 → Expected Rr = 48
q² = (0.4)² = 0.16 → Expected rr = 16
The observed values (36, 48, 16) match the expected values exactly. [1]
Therefore, this population is in Hardy-Weinberg equilibrium. [1]
Marking: Award 1 mark for showing the calculation or stating expected values, 1 mark for the correct conclusion. If the student calculates correctly and concludes "yes," award full marks.
13. Fossil evidence for evolution: [4]
- Fossils are the preserved remains or traces of organisms that lived in the past, found in sedimentary rock layers. [1]
- The fossil record shows that organisms have changed over time — older rock layers contain simpler organisms, while younger layers contain more complex organisms. Transitional fossils (e.g., Archaeopteryx) show intermediate forms between major groups. [1]
- The sequence of fossils in rock layers matches the order in which groups are thought to have evolved. [1]
- Limitation: The fossil record is incomplete because fossilisation is a rare event — most organisms decompose without leaving fossils. Soft-bodied organisms are especially underrepresented. Many fossils have also been destroyed by geological processes. [1]
Marking: Award 1 mark each for: (i) definition of fossils, (ii) change over time shown in the record, (iii) a valid limitation. The fourth mark is for a coherent, well-structured response covering all required points.
14. Homologous structures:
(a) Homologous structures [1]
(b) The similarity in bone structure suggests that the human, bat, and whale share a common ancestor that had the same basic forelimb bone pattern. [1] Over time, the structures were modified by natural selection for different functions in different environments (descent with modification). [1]
(c) These structures arise through descent with modification from a common ancestor. [1] Natural selection acted on variations in the ancestral population, and over many generations, the forelimb was adapted for different functions (grasping, flying, swimming) in different lineages, while retaining the underlying bone structure. [1]
Marking: Award marks as indicated. For (c), the answer must reference common ancestry and modification by natural selection.
15. Geographic isolation leading to speciation: [5]
- A population is split into two or more subpopulations by a physical barrier (e.g., a mountain range, river, canyon, or ocean). [1]
- Gene flow between the subpopulations is prevented — they can no longer interbreed. [1]
- The two subpopulations experience different environmental conditions and therefore different selection pressures. Mutations arise independently in each group. [1]
- Natural selection, genetic drift, and mutation cause the genetic composition of each subpopulation to diverge over many generations. [1]
- Eventually, the populations become so genetically different that they can no longer interbreed successfully even if they come back into contact. At this point, they are considered separate species (reproductive isolation has been achieved). [1]
Marking: Award 1 mark for each of the five logical steps. The sequence must be logical and complete. Accept equivalent phrasing.
16. Antibiotic resistance:
(a) Development of antibiotic resistance: [4]
- Within a bacterial population, there is genetic variation due to random mutations. Some bacteria may carry a mutation that makes them resistant to a particular antibiotic. [1]
- When the antibiotic is applied, non-resistant bacteria are killed. [1]
- Resistant bacteria survive and reproduce, passing the resistance gene to their offspring. [1]
- Over many generations, the frequency of the resistance allele increases in the population, and the population becomes predominantly resistant. [1]
Marking: Award 1 mark each for: (i) pre-existing variation/mutation, (ii) antibiotic kills non-resistant bacteria, (iii) resistant bacteria survive and reproduce, (iv) increase in resistance allele frequency over generations.
(b) Two practices to slow antibiotic resistance: [2]
(i) Complete the full course of antibiotics as prescribed (do not stop early when symptoms improve). [1]
(ii) Do not use antibiotics for viral infections (e.g., common cold, flu), as antibiotics only work against bacteria. [1]
Acceptable alternatives: Use antibiotics only when prescribed by a doctor; avoid using antibiotics in livestock as growth promoters; develop new antibiotics; use combination therapy; practise good hygiene to reduce infection spread. Award 1 mark per valid practice, max 2.
17. Phylogenetic tree interpretation:
(a) Species A and B are most closely related. [1] This is determined by the fact that they share the most recent common ancestor (their branching point/node is the most recent compared to other pairs). [1]
(b) A node (branching point) represents the most recent common ancestor of the species that descend from that point. [1]
(c) DNA sequences / amino acid (protein) sequences / anatomical (morphological) data / fossil data / embryological data (accept any one valid type). [1]
Marking: Award marks as indicated.
Section C: Data-Based & Extended Response (Questions 18–20)
18. Deer mouse body mass and natural selection:
(a) Trend: [2]
The average body mass of the deer mouse population increased steadily over the 20 generations, from approximately 18 g to approximately 24 g. [2]
Marking: Award 2 marks for a clear description that includes both the direction of change and approximate values. Award 1 mark if only the direction is stated without values.
(b) Natural selection explanation: [4]
- The environment became increasingly cold over the 20 generations. [1]
- Mice with larger body mass have a smaller surface area-to-volume ratio, which reduces heat loss and helps them maintain body temperature more efficiently in cold conditions. [1]
- Larger mice therefore had a survival and reproductive advantage in the cold environment. [1]
- These mice were more likely to survive, reproduce, and pass on the alleles associated for larger body mass to their offspring. Over many generations, the average body mass of the population increased. [1]
Marking: Award 1 mark each for the four points. The explanation must link the environmental change to the selective advantage of larger body mass.
(c) Prediction for warmer environment: [2]
The average body mass would likely decrease. [1]
In a warmer environment, smaller mice (with a larger surface area-to-volume ratio) would lose heat more efficiently and avoid overheating, giving them a survival advantage. Natural selection would favour smaller body mass, and the population mean would decrease over generations. [1]
Marking: Award 1 mark for the correct prediction and 1 mark for a valid explanation.
19. Grasshopper speciation scenario:
(a) Behavioural (prezygotic) isolation [1]
Accept "temporal isolation" if the student focuses on the difference in breeding seasons, or "behavioural isolation" if focusing on mating calls. Both are valid prezygotic barriers.
(b) The canyon acts as a physical barrier that prevents the grasshoppers from moving between the two populations. [1] This prevents gene flow (the exchange of alleles through interbreeding) between the two populations, allowing them to evolve independently. [1]
(c) Sequence to speciation: [4]
- The canyon physically separates the two populations, preventing gene flow. [1]
- The two populations experience different environmental conditions and selection pressures. Random mutations arise independently in each population. [1]
- Over many generations, natural selection, genetic drift, and mutation cause the genetic makeup of each population to diverge. Differences accumulate in traits such as mating calls and breeding seasons. [1]
- Eventually, the populations become so genetically and behaviourally different that even if they came into contact again, they would not recognise each other as mates or would not be able to breed at the same time. Reproductive isolation is complete, and they are now separate species. [1]
Marking: Award 1 mark for each logical step. The answer must describe a clear sequence from isolation to reproductive isolation.
(d) Reproductive isolation (or speciation) [1]
Marking: Award 1 mark for the correct term.
20. Darwin's finches passage:
(a) Evidence for evolution by natural selection: [4]
- The different finch species all descended from a common ancestor, showing that new species can arise from existing ones. [1]
- The variation in beak size and shape among the finches corresponds to different food sources on different islands. [1]
- On each island, finches with beak shapes best suited to the available food source had a survival and reproductive advantage. [1]
- Over many generations, natural selection caused the beak characteristics to diverge in different populations, leading to the formation of distinct species — this is adaptive radiation. [1]
Marking: Award 1 mark for each of the four points. The answer must link beak variation to natural selection and speciation.
(b) Different beak shapes on different islands: [3]
- Different islands have different available food sources (e.g., seeds of different sizes, insects, cactus flowers). [1]
- The ancestral finch population colonised different islands and became geographically isolated. [1]
- On each island, natural selection favoured the beak shape best suited to the local food source. Over time, the populations diverged and evolved into distinct species with different beak morphologies. [1]
Marking: Award 1 mark for each of the three points.
(c) Adaptive radiation [1]
Marking: Award 1 mark for the correct term.