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O Level Biology Plant Biology Quiz
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Questions
O-Level Biology Quiz - Plant Biology
Name: __________________________
Class: __________________________
Date: __________________________
Score: ______ / 40
Duration: 45 minutes
Total Marks: 40
Instructions:
- Answer all questions.
- Write your answers in the spaces provided.
- The number of marks is given in brackets [ ] at the end of each question or part question.
- You may use a calculator.
Section A: Multiple Choice (Questions 1–5)
Choose the correct answer and write the letter in the box provided.
1. Which structure is found in a palisade mesophyll cell but not in a root hair cell?
A. Cell wall
B. Cytoplasm
C. Chloroplast
D. Nucleus
Answer: [___] [1]
2. A student investigates the effect of light intensity on the rate of photosynthesis using an aquatic plant. Which gas is collected in the test tube?
A. Carbon dioxide
B. Oxygen
C. Nitrogen
D. Hydrogen
Answer: [___] [1]
3. Which of the following correctly describes the movement of water and sucrose in a plant?
A. Water moves in xylem; Sucrose moves in phloem
B. Water moves in phloem; Sucrose moves in xylem
C. Water moves in xylem; Sucrose moves in xylem
D. Water moves in phloem; Sucrose moves in phloem
Answer: [___] [1]
4. A leaf is tested for starch. It is boiled in ethanol, then iodine solution is added. The leaf turns blue-black. What does this indicate?
A. Chlorophyll has been removed.
B. Starch is present.
C. Glucose is present.
D. Protein is present.
Answer: [___] [1]
5. Which factor is NOT a limiting factor for photosynthesis at low light intensity on a warm, sunny day?
A. Light intensity
B. Carbon dioxide concentration
C. Temperature
D. Chlorophyll content
Answer: [___] [1]
Section B: Structured Questions (Questions 6–15)
6. Fig. 6.1 shows a cross-section of a leaf.
(Imagine a diagram showing: A = Upper Epidermis, B = Palisade Mesophyll, C = Spongy Mesophyll, D = Stoma, E = Guard Cell)
(a) Identify structures B and D.
B: __________________________
D: __________________________ [2]
(b) Explain how structure B is adapted for its function.
_________________________________________________________________________ [2]
(c) State the function of structure D.
_________________________________________________________________________ [1]
7. A student places a strip of potato into a concentrated sugar solution.
(a) Describe what happens to the mass of the potato strip after 30 minutes.
_________________________________________________________________________ [1]
(b) Explain this change using the term water potential.
_________________________________________________________________________ [3]
8. Describe the process of transpiration.
_________________________________________________________________________ [3]
9. Fig. 9.1 shows the effect of temperature on the rate of photosynthesis.
(Imagine a graph: X-axis = Temperature (°C), Y-axis = Rate of Photosynthesis. The line rises steeply from 10°C to 35°C, peaks at 35°C, and drops sharply to zero at 50°C.)
(a) State the optimum temperature for photosynthesis shown in the graph.
__________________________ °C [1]
(b) Explain why the rate of photosynthesis decreases sharply after 40°C.
_________________________________________________________________________ [2]
10. Mineral ions are absorbed by root hair cells.
(a) Name the process by which mineral ions are absorbed against a concentration gradient.
__________________________ [1]
(b) Explain why this process requires energy.
_________________________________________________________________________ [2]
11. Compare wind-pollinated flowers and insect-pollinated flowers.
Complete the table below:
| Feature | Wind-pollinated | Insect-pollinated |
|---|---|---|
| Petals | Small / dull / absent | __________________________ [1] |
| Pollen grains | Light / smooth / dusty | __________________________ [1] |
| Scent | None | __________________________ [1] |
12. Describe the route taken by a pollen tube from pollination to fertilisation.
_________________________________________________________________________ [3]
13. A farmer adds fertiliser containing nitrates to his crops.
(a) Why do plants need nitrates?
_________________________________________________________________________ [1]
(b) What is the likely effect on the plant if magnesium ions are deficient in the soil?
_________________________________________________________________________ [2]
14. Explain the term translocation in plants.
_________________________________________________________________________ [2]
15. Fig. 15.1 shows an experiment to investigate the factors affecting transpiration using a potometer.
(Imagine a diagram of a potometer with a leafy shoot, a capillary tube with an air bubble, and a beaker of water.)
(a) What does the movement of the air bubble measure?
_________________________________________________________________________ [1]
(b) Predict how the rate of bubble movement would change if a fan was placed near the plant. Explain your answer.
_________________________________________________________________________ [2]
Section C: Free Response Questions (Questions 16–20)
16. Describe the structural differences between xylem vessels and phloem sieve tubes.
_________________________________________________________________________ [4]
17. Explain how carbon dioxide enters a leaf and how it is used during photosynthesis.
_________________________________________________________________________ [4]
18. A plant is kept in the dark for 48 hours before being used in a starch test. Explain why this step is necessary.
_________________________________________________________________________ [3]
19. Discuss the advantages and disadvantages of self-pollination compared to cross-pollination.
_________________________________________________________________________ [4]
20. Explain how the structure of a root hair cell is adapted for the absorption of water.
_________________________________________________________________________ [4]
End of Quiz
Answers
O-Level Biology Quiz - Plant Biology (Answer Key)
Total Marks: 40
Section A: Multiple Choice
1. C [1]
Explanation: Root hair cells are underground and do not perform photosynthesis, so they lack chloroplasts. Palisade cells are in the leaf and contain many chloroplasts. Both have cell walls, cytoplasm, and nuclei.
2. B [1]
Explanation: Photosynthesis produces oxygen as a by-product, which is released as gas bubbles.
3. A [1]
Explanation: Xylem transports water and mineral ions; Phloem transports organic nutrients like sucrose (translocation).
4. B [1]
Explanation: Iodine solution turns blue-black in the presence of starch. Ethanol removes chlorophyll to make the colour change visible.
5. C [1]
Explanation: At low light intensity, light is the limiting factor. Temperature is already "warm," so it is not limiting the rate at that specific point compared to light.
Section B: Structured Questions
6. Leaf Structure
(a)
B: Palisade mesophyll [1]
D: Stoma (or Stomata) [1]
(b)
- Contains many chloroplasts to maximise light absorption for photosynthesis. [1]
- Located near the upper surface of the leaf to receive maximum light. [1]
(c)
- Allows for gas exchange (entry of CO₂ and exit of O₂/water vapour). [1]
7. Osmosis in Potato
(a)
- The mass of the potato strip decreases. [1]
(b)
- The concentrated sugar solution has a lower water potential than the potato cell sap. [1]
- Water moves out of the potato cells by osmosis. [1]
- Water moves from a region of higher water potential (inside cell) to lower water potential (outside) across the partially permeable membrane. [1]
8. Transpiration Process
- Transpiration is the loss of water vapour from the aerial parts of the plant (mainly leaves). [1]
- Water evaporates from the surface of mesophyll cells into the air spaces. [1]
- Water vapour diffuses out of the leaf through the stomata down a concentration gradient. [1]
9. Temperature and Photosynthesis
(a)
- 35°C [1]
(b)
- High temperatures cause the enzymes involved in photosynthesis to denature. [1]
- The active site of the enzyme changes shape, so the substrate can no longer bind, stopping the reaction. [1]
10. Mineral Ion Absorption
(a)
- Active transport [1]
(b)
- Active transport moves substances against the concentration gradient (from low to high concentration). [1]
- This requires energy (ATP) produced by respiration in the mitochondria. [1]
11. Pollination Comparison
- Insect-pollinated Petals: Large / bright / coloured [1]
- Insect-pollinated Pollen: Sticky / spiky / large [1]
- Insect-pollinated Scent: Present / strong / sweet [1]
12. Pollen Tube Route
- The pollen grain lands on the stigma. [1]
- It germinates and grows a pollen tube down through the style. [1]
- The pollen tube enters the ovule through the micropyle and releases male gametes for fertilisation. [1]
13. Mineral Deficiencies
(a)
- To make amino acids / proteins / chlorophyll (for growth). [1]
(Note: Nitrates are primarily for amino acids/proteins, but often linked to general growth. Magnesium is for chlorophyll.)
(b)
- The leaves will turn yellow (chlorosis). [1]
- Because magnesium is needed to make chlorophyll, and without it, photosynthesis is reduced. [1]
14. Translocation
- Translocation is the transport of organic nutrients (such as sucrose and amino acids). [1]
- It occurs in the phloem from sources (e.g., leaves) to sinks (e.g., roots, fruits). [1]
15. Potometer Experiment
(a)
- The rate of water uptake (which approximates the rate of transpiration). [1]
(b)
- The rate of bubble movement would increase. [1]
- The fan increases air movement/wind, which removes water vapour from around the leaf. [1]
- This maintains a steep concentration gradient for diffusion, increasing transpiration. [1]
(Note: Only 2 marks available, so any two of the above points.)
Section C: Free Response Questions
16. Xylem vs Phloem Structure
- Xylem: Made of dead, hollow cells with no cytoplasm or nucleus. [1]
- Xylem: Walls are thickened with lignin for strength and waterproofing. [1]
- Phloem: Made of living cells (sieve tube elements and companion cells). [1]
- Phloem: Sieve plates have pores to allow flow of sap; companion cells provide metabolic support. [1]
17. CO₂ Entry and Use
- CO₂ enters the leaf through the stomata by diffusion. [1]
- It moves into the air spaces and dissolves in the moisture on the surface of mesophyll cells. [1]
- It diffuses into the chloroplasts. [1]
- In the chloroplasts, CO₂ is used in the light-independent reaction (Calvin cycle) to produce glucose/starch using energy from ATP and NADPH. [1]
18. Destarching
- To remove any existing starch stored in the leaves from previous photosynthesis. [1]
- This ensures that any starch detected after the experiment was produced during the experiment. [1]
- If not destarched, the result would be invalid as we wouldn't know if the starch was new or old. [1]
19. Self vs Cross Pollination
- Advantage of Self: Does not depend on external agents (wind/insects); ensures reproduction even if isolated. [1]
- Disadvantage of Self: No genetic variation; offspring are genetically identical, making them vulnerable to disease/environmental change. [1]
- Advantage of Cross: Produces genetic variation; allows for evolution and adaptation to changing environments. [1]
- Disadvantage of Cross: Depends on external agents; energy required to produce nectar/scents; chance of pollination is not guaranteed. [1]
20. Root Hair Cell Adaptation
- Large Surface Area: The long hair-like projection greatly increases the surface area for absorption of water and minerals. [1]
- Thin Cell Wall: The cell wall is thin, reducing the distance for water to diffuse/osmose into the cell. [1]
- High Solute Concentration: The cell sap has a lower water potential (higher solute concentration) than the soil water, facilitating water entry by osmosis. [1]
- Many Mitochondria: Provide energy (ATP) for the active transport of mineral ions. [1]