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Secondary 4 Pure Biology Evolution Diversity Quiz

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Secondary 4 Pure 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 or part-question is shown in brackets [ ].
Where diagrams or data are provided, use them to support your answers.
This quiz covers the topic Evolution and Diversity only.

Section A: Multiple Choice (Questions 1–5) [10 marks]

Each question carries 2 marks. Choose the most accurate answer.

1. Which of the following best describes natural selection?

A. Organisms choose which traits to pass on to their offspring.
B. Individuals with advantageous traits are more likely to survive and reproduce.
C. All members of a population evolve simultaneously in response to environmental change.
D. Mutations occur only when the environment demands a new trait.

Answer: _______________

2. The diagram below shows the variation in beak depth in a population of finches before and after a drought.

Before drought:          After drought:
    ▁▂▃▄▅▆▇█▇▆▅▄▃▂▁        ▁▁▂▃▄▅▆▇█▆▅▄▃▁▁
    (wide range,            (shifted toward
     centred at 10mm)        deeper beaks, ~13mm)

What type of selection is illustrated?

A. Stabilising selection
B. Directional selection
C. Disruptive selection
D. Artificial selection

Answer: _______________

3. Which statement about speciation is correct?

A. Speciation occurs when two populations look different from each other.
B. Speciation requires geographic isolation in all cases.
C. Speciation results from reproductive isolation between populations over time.
D. Speciation happens within a single generation when a mutation arises.

Answer: _______________

4. A fossil record shows that a species of trilobite remained morphologically unchanged for millions of years, then was replaced abruptly by a distinctly different form. This pattern best supports which model of evolution?

A. Gradualism
B. Punctuated equilibrium
C. Convergent evolution
D. Genetic drift

Answer: _______________

5. Which of the following is the best evidence that two species share a recent common ancestor?

A. They live in the same habitat.
B. They have similar body sizes.
C. They share a high percentage of identical DNA sequences.
D. They occupy the same ecological niche.

Answer: _______________

Section B: Short Answer and Structured Response (Questions 6–15) [20 marks]

6. Define the term gene pool. [2]

7. State two conditions that must be met for a population to be in Hardy–Weinberg equilibrium. [2]

(a) ___________________________________________________________________________

(b) ___________________________________________________________________________

8. Table 1 shows the number of light-coloured and dark-coloured peppered moths (Biston betularia) recorded in two English towns over a 10-year period during industrial pollution.

Year	Town A – Light moths	Town A – Dark moths	Town B – Light moths	Town B – Dark moths
1	120	30	95	55
5	60	90	70	80
10	25	125	50	100

(a) Describe the trend in the population of dark-coloured moths in Town A over the 10-year period. [2]

(b) Suggest an explanation for the change observed in both towns. [2]

9. Distinguish between convergent evolution and divergent evolution, giving one named example of each. [4]

Convergent evolution: ___________________________________________________________

Example: _______________________________________________________________________

Divergent evolution: ___________________________________________________________

Example: _______________________________________________________________________

10. Explain why genetic drift has a greater effect on small populations than on large populations. [2]

11. Fig. 1 (described below) shows the pentadactyl limb structure in five different vertebrate species.

Description of Fig. 1: The diagram shows the forelimb skeleton of a human, a bat, a whale, a horse, and a lizard. All share the same basic bone pattern — one upper arm bone (humerus), two forearm bones (radius and ulna), small wrist bones, and five digits — but the bones differ in shape, size, and proportion.

(a) What term describes structures like these that share a common origin but may serve different functions? [1]

(b) What do such structures suggest about the evolutionary relationship among these species? [2]

12. A population of beetles shows variation in colour — green and brown. Birds prey on the beetles. In a grassy environment, green beetles are better camouflaged.

(a) Explain how natural selection would act on this beetle population in the grassy environment over several generations. [3]

(b) If the environment changed to a dry, brown soil habitat, predict what would happen to the frequency of the brown allele over time. Explain your reasoning. [2]

13. State two sources of genetic variation in a population. [2]

(a) ___________________________________________________________________________

(b) ___________________________________________________________________________

14. Explain how geographic isolation can lead to the formation of new species. Use a named example in your answer. [3]

15. The Galápagos finches are a classic example of adaptive radiation.

(a) Define adaptive radiation. [2]

(b) Explain why the Galápagos Islands provided ideal conditions for adaptive radiation to occur. [2]

Section C: Extended Response (Questions 16–20) [10 marks]

16. Antibiotic resistance in bacteria is an example of evolution by natural selection.

Explain, step by step, how a population of bacteria can become resistant to an antibiotic over time. In your answer, refer to variation, selection pressure, reproduction, and the change in allele frequency. [5]

17. Fig. 2 (described below) shows a phylogenetic tree of five species (A, B, C, D, and E).

Description of Fig. 2: Species A and B share a common ancestor at Node 1. Species C branches off at Node 2, which is ancestral to the A–B–C clade. Species D and E share a common ancestor at Node 3. Node 4 is the root connecting the (A,B,C) clade to the (D,E) clade.

(a) Which two species are most closely related? Explain how you determined this. [2]

(b) Which species is the outgroup to the clade containing species A, B, and C? [1]

(c) A new fossil discovery shows traits intermediate between the ancestor at Node 2 and species C. What does this suggest about the evolutionary pathway of species C? [2]

18. Fossil evidence, comparative anatomy, and molecular biology are three lines of evidence used to support the theory of evolution.

For each line of evidence, describe one specific example and explain how it supports evolutionary theory. [3]

Fossil evidence: ______________________________________________________________

Comparative anatomy: __________________________________________________________

Molecular biology: _____________________________________________________________

19. Some scientists argue that the evolution of the horse (Equus) from Hyracotherium (a small, multi-toed ancestor) occurred gradually over 50 million years. Others propose that the changes happened in rapid bursts separated by long periods of stasis.

(a) Name the two models of evolution described above. [2]

(i) __________________________________________________________________________

(ii) __________________________________________________________________________

(b) Describe one piece of evidence that would support the model described in (a)(ii). [1]

20. A student claims: "Evolution means organisms become more complex and 'better' over time."

Evaluate this statement. In your answer, explain whether the statement is accurate, and describe at least two reasons why the student's understanding of evolution is incomplete or incorrect. [2]

End of Quiz

Answers

Secondary 4 Pure Biology Quiz — Evolution Diversity

Answer Key

Section A: Multiple Choice

1. B
[2 marks]
Natural selection is the process by which individuals with traits that confer a survival or reproductive advantage in a given environment are more likely to pass those traits to the next generation.
Common mistake: Choosing A implies Lamarckian inheritance (organisms "choosing" traits), which is incorrect. Choosing C is wrong because evolution acts on populations over generations, not simultaneously.

2. B
[2 marks]
The graph shows a shift in the mean beak depth toward one extreme (deeper beaks), which is characteristic of directional selection. After the drought, harder seeds were likely more abundant, favouring finches with deeper, stronger beaks.
Common mistake: Students may select stabilising selection if they confuse a shift with a narrowing of the range.

3. C
[2 marks]
Speciation is the process by which populations become reproductively isolated and diverge genetically to the point where they can no longer interbreed to produce fertile offspring.
Common mistake: Choosing B — geographic isolation is one mechanism (allopatric speciation) but not the only route; sympatric speciation can occur without it.

4. B
[2 marks]
Punctuated equilibrium describes long periods of little change (stasis) interrupted by relatively rapid bursts of evolutionary change. This contrasts with gradualism, which predicts slow, continuous change.
Common mistake: Students may choose gradualism if they focus on the "millions of years" without noticing the abrupt replacement.

5. C
[2 marks]
DNA sequence similarity is the most reliable indicator of common ancestry because DNA is inherited directly from ancestors. The more similar the DNA, the more recently two species diverged from a common ancestor.
Common mistake: Choosing A or D — shared habitat or niche may result from convergent evolution, not common ancestry.

Section B: Short Answer and Structured Response

6. The gene pool is the total collection of all the genes (and their alleles) present in a population at a given time. [2]
Marking notes: Award 1 mark for "all the genes/alleles" and 1 mark for specifying "in a population." Answers that only say "all the genes in an organism" are incorrect.

7. Any two of the following: [1 mark each, total 2]
(a) No mutations occur.
(b) The population is very large (no genetic drift).
(c) Mating is random.
(d) There is no natural selection (all individuals have equal reproductive success).
(e) There is no migration (no gene flow into or out of the population).
Marking notes: Students need only state two. Accept equivalent phrasing, e.g., "large population size" or "no emigration or immigration."

8. (a) The number of dark-coloured moths in Town A increased steadily over the 10-year period, from 30 in Year 1 to 125 in Year 10. [2]
Marking notes: Award 1 mark for identifying the increase, 1 mark for referencing specific data (e.g., "from 30 to 125" or quoting figures from the table).

(b) During the Industrial Revolution, soot from factories darkened tree bark. Dark-coloured moths were better camouflaged against predators (birds), so they survived and reproduced more successfully than light-coloured moths. Over time, the frequency of the dark allele increased in the population. [2]
Marking notes: Award 1 mark for linking pollution/darkened surfaces to camouflage, and 1 mark for explaining differential survival/reproduction (natural selection). Answers that only say "pollution killed the light moths" without explaining selection are incomplete.

9. Convergent evolution is the process by which unrelated species independently evolve similar traits as a result of adapting to similar environments or ecological niches. [1]
Example: The streamlined body shape of sharks (fish) and dolphins (mammals), or the wings of insects and birds. [1]

Divergent evolution is the process by which related species evolve different traits, often due to adaptation to different environments, leading to speciation. [1]
Example: Darwin's finches on the Galápagos Islands, which evolved different beak shapes from a common ancestor. [1]

Marking notes: Examples must be named (not just described vaguely). Award 1 mark for each correct definition and 1 mark for each valid example.

10. Genetic drift is the random change in allele frequencies due to chance events. In a small population, chance events (e.g., a few individuals dying before reproducing) can significantly alter the allele frequencies because each individual represents a larger proportion of the gene pool. In a large population, the effect of random events is averaged out and has minimal impact on overall allele frequencies. [2]
Marking notes: Award 1 mark for defining genetic drift or stating it is random, and 1 mark for explaining why small populations are more affected (each individual has a greater proportional impact).

11. (a) Homologous structures. [1]

(b) These structures suggest that the five species share a common ancestor from which the basic pentadactyl limb pattern was inherited. The differences in bone shape and size reflect adaptations to different functions (e.g., flying, swimming, running, grasping) over evolutionary time. [2]
Marking notes: Award 1 mark for stating common ancestry, 1 mark for linking structural differences to functional adaptation. Answers that only say "they look similar" without mentioning common origin are incomplete.

12. (a) In the grassy environment, green beetles are better camouflaged from bird predators than brown beetles. Green beetles therefore have a higher chance of surviving and reproducing, passing the green allele to their offspring. Over several generations, the frequency of the green allele increases in the population, while the frequency of the brown allele decreases. This is natural selection acting on a heritable trait. [3]
Marking notes: Award 1 mark for linking camouflage to reduced predation, 1 mark for differential survival/reproduction, and 1 mark for stating the change in allele frequency over generations.

(b) The frequency of the brown allele would increase over time. In a brown soil environment, brown beetles would be better camouflaged and less likely to be eaten by birds. Brown beetles would survive and reproduce more successfully, passing the brown allele to offspring. Natural selection would favour the brown phenotype. [2]
Marking notes: Award 1 mark for predicting the increase in brown allele frequency, 1 mark for explaining the mechanism (camouflage → differential survival → reproduction).

13. Any two of the following: [1 mark each]
(a) Mutation
(b) Sexual reproduction / random fertilisation / crossing over during meiosis / independent assortment
(c) Gene flow (migration of individuals between populations)
Marking notes: Accept equivalent phrasing. "Genetic recombination" is acceptable for (b).

14. Geographic isolation occurs when a physical barrier (e.g., a mountain range, river, or ocean) separates a population into two or more groups. The separated populations experience different environmental conditions and selection pressures. Over time, genetic differences accumulate through natural selection, mutation, and genetic drift. Eventually, the populations become so genetically different that they can no longer interbreed to produce fertile offspring — they have become separate species. [2 for mechanism + 1 for example]

Example: The Galápagos finches — ancestral finches colonised different islands, became geographically isolated, and adapted to different food sources on each island, leading to the evolution of multiple species with distinct beak shapes. [1]

Marking notes: Award up to 2 marks for a clear explanation of the mechanism (barrier → different selection → genetic divergence → reproductive isolation) and 1 mark for a named example. Answers without an example lose 1 mark.

15. (a) Adaptive radiation is the rapid evolution of many species from a single common ancestor, each adapted to a different ecological niche. [2]
Marking notes: Award 1 mark for "many species from one ancestor" and 1 mark for "different niches/environments."

(b) The Galápagos Islands provided a variety of unoccupied ecological niches (different food sources, habitats) with few competing species. This allowed the ancestral finch population to diversify and adapt to different niches on different islands, driven by natural selection and geographic isolation. [2]
Marking notes: Award 1 mark for mentioning available/vacant niches, and 1 mark for linking this to diversification (natural selection or isolation).

Section C: Extended Response

16. [5 marks]
Step-by-step explanation:

Variation exists: Within a bacterial population, genetic variation arises through random mutations. Some bacteria may carry a mutation that confers resistance to a particular antibiotic (e.g., a change in the target protein or an enzyme that breaks down the antibiotic). [1]
Selection pressure: When the antibiotic is introduced, it acts as a selection pressure. Non-resistant bacteria are killed or inhibited from reproducing. [1]
Differential survival and reproduction: Resistant bacteria survive the antibiotic treatment and reproduce, passing the resistance gene to their offspring. [1]
Change in allele frequency: Over successive generations, the frequency of the resistance allele increases in the population because resistant individuals contribute more offspring to the next generation. [1]
Result: Eventually, the majority (or all) of the bacterial population carries the resistance allele, and the antibiotic becomes ineffective. This is evolution by natural selection. [1]

Marking notes: Award 1 mark for each of the five key points above. Answers that omit variation or allele frequency change lose the corresponding mark. Award a maximum of 4 marks if the answer is well-structured but misses one key concept.

17. (a) Species A and B are most closely related. [1] This is determined by identifying the most recent common ancestor — A and B share Node 1, which is the most recent branching point compared to the nodes connecting the other species. [1]

(b) Species D (or E) is the outgroup to the A–B–C clade. [1]
Marking notes: Accept either D or E, as both are equally distant from the A–B–C clade. The outgroup is the species that branches off earliest from the clade in question.

(c) The fossil with intermediate traits suggests that species C evolved gradually from the ancestor at Node 2 through a series of small, incremental changes. This supports the gradualism model of evolution, as it shows a transitional form linking the ancestor to the modern species. [2]
Marking notes: Award 1 mark for identifying gradual change/transitional form, and 1 mark for linking it to gradualism or the evolutionary pathway.

18. [3 marks — 1 mark per line of evidence]

Fossil evidence: The fossil record shows a chronological sequence of life forms, with simpler organisms in older rock layers and more complex organisms in younger layers. For example, transitional fossils such as Archaeopteryx (which has both reptilian and avian features) provide evidence of evolutionary links between major groups. [1]

Comparative anatomy: Homologous structures, such as the pentadactyl limb in vertebrates, indicate common ancestry despite differences in function. The similar bone arrangement in the forelimbs of humans, bats, whales, and horses suggests descent from a shared ancestor. [1]

Molecular biology: Comparing DNA or protein sequences between species reveals degrees of similarity that reflect evolutionary relationships. For example, humans and chimpanzees share approximately 98–99% of their DNA, indicating a recent common ancestor. [1]

Marking notes: Award 1 mark for each line of evidence that includes both a specific example and a clear explanation of how it supports evolution. Vague answers (e.g., "fossils show change over time" without an example) receive 0.5 marks.

19. (a) (i) Gradualism [1]
(ii) Punctuated equilibrium [1]

(b) The fossil record showing long periods with no morphological change (stasis) in a species, followed by the sudden appearance of a distinctly different form without intermediate transitional fossils, would support punctuated equilibrium. [1]
Marking notes: Award 1 mark for describing stasis and sudden change in the fossil record. Answers that only say "the fossil record" without elaboration receive 0 marks.

20. [2 marks]
The student's statement is inaccurate for the following reasons:

Evolution does not necessarily lead to greater complexity. Some organisms have evolved to become simpler over time (e.g., parasites losing complex organ systems). Evolution favours traits that improve reproductive success in a given environment, not complexity. [1]
Evolution does not have a direction toward "better." Natural selection favours traits that are advantageous in a specific environment, not traits that are universally "better." What is advantageous in one environment may be disadvantageous in another. Evolution is not goal-oriented or progressive. [1]

Marking notes: Award 1 mark for each valid reason (maximum 2). Answers that only say "the student is wrong" without explanation receive 0 marks. Accept other valid points, such as: evolution acts on populations, not individuals; "better" is subjective and environment-dependent.

End of Answer Key