Secondary 4 Pure Biology Ecology Quiz

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Secondary 4 Pure Biology Quiz - Ecology

Name: ______________________
Class: ______________________
Date: ______________________
Score: ______________________

Duration: 60 minutes
Total Marks: 40

Instructions:

• Answer all 20 questions.
• Section A: Multiple Choice (1 mark each)
• Section B: Short Structured Questions (1–3 marks each)
• Section C: Data Interpretation & Extended Response (2–5 marks each)
• Write your answers clearly in the spaces provided.

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Section A: Multiple Choice (Questions 1–5)

1. Which of the following best describes a community in an ecosystem?
   A. All the physical factors in a habitat
   B. All the populations of different species living together
   C. A single species in a given area
   D. The non-living components of the environment
   _____ (1 mark)

2. In a food chain, the organism that produces its own food using sunlight is called a:
   A. consumer
   B. decomposer
   C. producer
   D. parasite
   _____ (1 mark)

3. Which process returns carbon dioxide to the atmosphere?
   A. Photosynthesis
   B. Respiration
   C. Diffusion into oceans
   D. Fossilisation
   _____ (1 mark)

4. A population is defined as:
   A. All organisms in a habitat
   B. Members of one species in a given area
   C. All producers in a food web
   D. The total biomass of an ecosystem
   _____ (1 mark)

5. Which of these is a biotic factor?
   A. Temperature
   B. Soil pH
   C. Predation
   D. Rainfall
   _____ (1 mark)

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Section B: Short Structured Questions (Questions 6–10)

6. State one abiotic factor and one biotic factor that can affect the size of a fish population in a pond.
   Abiotic: ______________________
   Biotic: ______________________ (2 marks)

7. Name the process by which green plants convert light energy into chemical energy. (1 mark)

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8. The diagram below shows a simple food chain.
   Grass → Grasshopper → Frog → Snake
   State the trophic level of the frog. (1 mark)

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9. Explain why decomposers are important in the nitrogen cycle. (2 marks)

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10. Give one example of a producer and one example of a primary consumer in a terrestrial ecosystem. (2 marks)
    Producer: ______________________
    Primary consumer: ______________________

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Section C: Data Interpretation & Extended Response (Questions 11–20)

11. The graph shows the population sizes of two species in a predator–prey relationship over 20 years.

Image pending generation: graph for Q11.

(a) Describe the pattern shown by the two populations. (2 marks)

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(b) Explain why the predator population lags behind the prey population. (2 marks)

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12. Define the term "ecological niche". (2 marks)

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13. A student sets up a pond ecosystem in a sealed jar with pondweed, snails, and water.
    (a) Name the producer in this ecosystem. (1 mark)

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    (b) State one gas that the pondweed releases during the day and how it benefits the snail. (2 marks)

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14. The table shows the energy transferred at each trophic level in a grassland ecosystem.

Trophic level	Energy (kJ/m²/yr)
Producers	5000
Primary cons.	500
Secondary cons.	50

Calculate the percentage of energy transferred from producers to primary consumers. Show your working. (2 marks)

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15. Explain how deforestation can lead to an increase in atmospheric carbon dioxide. (3 marks)

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16. The diagram shows a nitrogen cycle.

Image pending generation: diagram for Q16.

Name the process by which nitrates are converted back to atmospheric nitrogen. (1 mark)

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17. A lake is polluted with excess fertiliser, causing algal blooms.
    (a) State the term for this nutrient enrichment process. (1 mark)

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    (b) Explain how the algal bloom can lead to death of fish. (3 marks)

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18. Compare the roles of producers and decomposers in an ecosystem. (3 marks)

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19. The figure shows a transect line across a shore with bands of organisms.

Image pending generation: diagram for Q19.

(a) What is meant by zonation? (1 mark)

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(b) Suggest one reason why seaweed is found only in the low tide zone. (2 marks)

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20. Evaluate the use of biological control instead of chemical pesticides in agriculture. (5 marks)

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Secondary 4 Pure Biology Quiz - Ecology (Answer Key)

Total Marks: 40
Topic: Ecology

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Section A: Multiple Choice

1. B (1 mark)
   Teaching note: A community = all populations of different species living in the same habitat. A is habitat physical factors (abiotic), C is a population, D is abiotic environment.

2. C (1 mark)
   Teaching note: Producers (e.g. green plants) make food by photosynthesis using sunlight. Consumers eat others; decomposers break down dead matter.

3. B (1 mark)
   Teaching note: Respiration in plants, animals, fungi, and microbes releases CO₂. Photosynthesis removes CO₂.

4. B (1 mark)
   Teaching note: Population = same species, same area. A is community + abiotic; C is trophic group.

5. C (1 mark)
   Teaching note: Biotic = living factors. Predation involves organisms. A, B, D are abiotic (non-living).

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Section B: Short Structured

6. Abiotic: temperature / dissolved oxygen / pH (1 mark)
   Biotic: predation / competition / disease (1 mark)
   Teaching note: Abiotic = non-living; biotic = living. Any valid example per category earns the mark.

7. Photosynthesis (1 mark)
   Teaching note: Light energy → chemical energy in glucose.

8. Secondary consumer (1 mark)
   Teaching note: Grass (prod) → grasshopper (primary cons) → frog (secondary cons) → snake (tertiary cons).

9. Decomposers break down dead organisms and waste, releasing ammonia/nitrates for plants (2 marks: 1 for breakdown, 1 for nutrient return)
   Teaching note: Without decomposers, nitrogen remains locked in dead matter.

10. Producer: any plant (e.g. grass) (1 mark)
    Primary consumer: herbivore (e.g. rabbit) (1 mark)
    Teaching note: Producer makes own food; primary consumer eats producer.

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Section C: Data Interpretation & Extended

11. (a) Prey and predator populations show cyclical rises and falls; predator peaks occur after prey peaks (2 marks: 1 cycle described, 1 lag noted)
    (b) Predator numbers depend on prey as food; when prey increases, predators reproduce and rise, but with delay (2 marks)
    Teaching note: Link graph lag to food dependency.

12. Role/position of a species in ecosystem including habitat, food, interactions (2 marks)
    Teaching note: Niche ≠ habitat; includes function.

13. (a) Pondweed (1 mark)
    (b) Oxygen; used by snail for respiration (2 marks: gas 1, benefit 1)
    Teaching note: Pondweed photosynthesises in light, releasing O₂.

14. % = (500 / 5000) × 100 = 10% (2 marks: 1 formula, 1 answer)
    Working: 500 ÷ 5000 = 0.1; ×100 = 10%.

15. Trees cut → less photosynthesis to absorb CO₂ (1); burning/decomposition releases CO₂ (1); total atmospheric CO₂ rises (1) (3 marks)
    Teaching note: Deforestation reduces sinks and adds source.

16. Denitrification (1 mark)
    Teaching note: Nitrates → N₂ by denitrifying bacteria.

17. (a) Eutrophication (1 mark)
    (b) Algae block light (1); plants die (1); decomposers use O₂, fish suffocate (1) (3 marks)
    Teaching note: Chain of effects from bloom to hypoxia.

18. Producers make food via photosynthesis (1); decomposers recycle nutrients from dead matter (1); both maintain ecosystem energy/matter flow (1) (3 marks)

19. (a) Distribution of species in bands due to environmental gradient (1 mark)
    (b) Low zone stays wet/submerged; seaweed needs water to avoid desiccation (2 marks)
    Teaching note: Zonation caused by tolerance to exposure.

20. Biological control: uses natural predators (1); less pollution (1); but slower/less predictable (1); chemical: fast but harms non-target (1); overall balanced judgement (1) (5 marks: descriptors – 2 points each side + conclusion)