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Secondary 4 Pure Biology Plant Biology Quiz
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Questions
Secondary 4 Pure Biology Quiz - Plant Biology
Name: __________________________
Class: __________________________
Date: ___________________________
Score: ________ / 45
Duration: 45 minutes
Total Marks: 45
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.
- Diagrams are not drawn to scale unless stated.
Section A: Multiple Choice Questions (Questions 1–5)
Choose the correct answer and write the letter in the box provided.
1. Which of the following correctly describes the movement of water and mineral ions into a root hair cell?
| Water | Mineral Ions | |
|---|---|---|
| A | Active Transport | Diffusion |
| B | Osmosis | Active Transport |
| C | Osmosis | Diffusion |
| D | Diffusion | Active Transport |
Answer: [____] [1]
2. A student investigates the effect of light intensity on the rate of photosynthesis using an aquatic plant. The student counts the number of bubbles produced per minute at different distances from a lamp. Which variable must be kept constant to ensure a fair test?
A. The number of bubbles produced
B. The distance of the lamp from the plant
C. The concentration of carbon dioxide in the water
D. The time taken for the experiment
Answer: [____] [1]
3. The diagram shows a cross-section of a leaf.
A
/ \
| B |
\ /
C
Which layer contains the highest density of chloroplasts to maximize light absorption?
A. Upper epidermis
B. Palisade mesophyll
C. Spongy mesophyll
D. Lower epidermis
Answer: [____] [1]
4. Which process is responsible for the transport of sucrose from the leaves to the roots in a flowering plant?
A. Transpiration
B. Translocation
C. Osmosis
D. Active Transport
Answer: [____] [1]
5. A potted plant is left in a hot, dry, and windy environment for several hours. What happens to the guard cells and the stomata?
| Guard Cells | Stomata | |
|---|---|---|
| A | Become turgid | Open |
| B | Become turgid | Close |
| C | Become flaccid | Open |
| D | Become flaccid | Close |
Answer: [____] [1]
Section B: Structured Questions (Questions 6–15)
6. Fig. 6.1 shows a diagram of a root hair cell.
(a) State one structural feature of the root hair cell that increases its surface area for absorption.
_________________________________________________________________________ [1]
(b) Explain why root hair cells do not contain chloroplasts.
_________________________________________________________________________ [2]
(c) Mineral ions are absorbed by root hair cells even when the concentration of ions in the soil is lower than in the cell sap.
Name the process involved and state the source of energy for this process.
Process: __________________________
Energy Source: __________________________ [2]
7. Photosynthesis is summarized by the equation:
(a) Name the organic product .
_________________________________________________________________________ [1]
(b) Describe the role of chlorophyll in this process.
_________________________________________________________________________ [2]
(c) A plant is kept in darkness for 48 hours before being used in an experiment to test for starch. Explain why this step is necessary.
_________________________________________________________________________ [2]
8. Fig. 8.1 shows a graph of the rate of photosynthesis against light intensity at two different temperatures, 20°C and 30°C.
(Imagine a graph where the rate increases linearly then plateaus. The 30°C line plateaus at a higher rate than the 20°C line.)
(a) Identify the limiting factor for photosynthesis at point X, where light intensity is low and both lines overlap.
_________________________________________________________________________ [1]
(b) Explain why the rate of photosynthesis is higher at 30°C than at 20°C at high light intensities.
_________________________________________________________________________ [3]
(c) Suggest why the rate of photosynthesis decreases if the temperature is raised to 45°C.
_________________________________________________________________________ [2]
9. Transpiration is the loss of water vapor from the aerial parts of a plant.
(a) Name the tissue responsible for transporting water up the stem.
_________________________________________________________________________ [1]
(b) Explain how the cohesion-tension theory helps water move up a tall tree against gravity.
_________________________________________________________________________ [3]
(c) A student uses a potometer to measure the rate of water uptake. Explain why water uptake is not exactly the same as the rate of transpiration.
_________________________________________________________________________ [2]
10. Fig. 10.1 shows a cross-section of a stem stained to reveal vascular bundles.
(a) State the function of the phloem.
_________________________________________________________________________ [1]
(b) Describe the structural differences between xylem vessels and phloem sieve tubes.
_________________________________________________________________________ [3]
11. A farmer adds fertilizer containing nitrates to his crop.
(a) Why are nitrates essential for plant growth?
_________________________________________________________________________ [1]
(b) If the soil becomes waterlogged, the roots may die. Explain why, referring to respiration.
_________________________________________________________________________ [3]
12. The diagram below shows the internal structure of a leaf.
(a) Name the layer of cells labeled D that allows gas exchange.
_________________________________________________________________________ [1]
(b) Explain how the large air spaces in the spongy mesophyll aid in photosynthesis.
_________________________________________________________________________ [2]
13. An experiment is set up to investigate the effect of wind speed on transpiration.
(a) Predict the effect of increasing wind speed on the rate of transpiration.
_________________________________________________________________________ [1]
(b) Explain your prediction in terms of water vapor concentration gradient.
_________________________________________________________________________ [3]
14. Compare the functions of the cuticle and the stomata in a leaf.
| Feature | Cuticle | Stomata |
|---|---|---|
| Main Function | __________________________ | __________________________ |
| Permeability to Water | __________________________ | __________________________ |
[4]
15. Explain why most living organisms depend on photosynthesis, even if they do not perform photosynthesis themselves.
_________________________________________________________________________ [3]
Section C: Free Response Questions (Questions 16–20)
16. Describe the pathway taken by a water molecule from the soil into the root hair cell, through the root cortex, and into the xylem.
_________________________________________________________________________ [4]
17. Explain the mechanism of stomatal opening in the light. Include the role of potassium ions and water potential in your answer.
_________________________________________________________________________ [4]
18. A plant is placed in a solution of high salt concentration.
(a) Describe what will happen to the plant cells.
_________________________________________________________________________ [2]
(b) Explain the process causing this change, using the term water potential.
_________________________________________________________________________ [3]
19. Discuss the importance of transpiration to a plant. Give two benefits and one potential disadvantage.
Benefit 1: _______________________________________________________________
Benefit 2: _______________________________________________________________
Disadvantage: ___________________________________________________________
_________________________________________________________________________ [4]
20. Explain how the structure of a leaf is adapted for efficient photosynthesis. Refer to at least three specific adaptations.
_________________________________________________________________________ [5]
End of Quiz
Answers
Secondary 4 Pure Biology Quiz - Plant Biology (Answer Key)
Total Marks: 45
Section A: Multiple Choice Answers
- B [1]
Water moves by osmosis (high to low water potential). Mineral ions often move against concentration gradient via active transport. - C [1]
CO2 concentration, temperature, and plant health must be controlled. Distance is the independent variable; bubbles are the dependent variable. - B [1]
Palisade mesophyll cells are packed with chloroplasts and located at the top of the leaf to capture maximum light. - B [1]
Translocation is the transport of organic nutrients (sucrose/amino acids) in phloem. - D [1]
In hot/dry/windy conditions, water loss exceeds uptake. Guard cells lose turgor (become flaccid), causing stomata to close to prevent wilting.
Section B: Structured Answers
6.
(a) Long hair-like projection / root hair. [1]
(b) Root hair cells are located underground / in the soil [1]. They do not receive light, so they cannot perform photosynthesis / do not need chloroplasts. [1]
(c) Process: Active Transport [1]. Energy Source: Respiration (ATP) / Mitochondria. [1]
7.
(a) Glucose. [1]
(b) Chlorophyll absorbs light energy [1]. This energy is used to split water molecules / convert light energy to chemical energy. [1]
(c) To destarch the plant / remove existing starch [1]. This ensures that any starch detected after the experiment was produced during the experiment, not stored previously. [1]
8.
(a) Light intensity. [1]
(b) Photosynthesis involves enzymes [1]. At 30°C, enzymes have more kinetic energy / collide more frequently with substrates than at 20°C [1]. The rate of reaction is higher until another factor becomes limiting. [1]
(c) High temperature denatures the enzymes [1]. The active site changes shape, and the substrate no longer fits / enzyme-substrate complexes cannot form. [1]
9.
(a) Xylem. [1]
(b) Water molecules are cohesive (stick together) due to hydrogen bonding [1]. As water evaporates from leaves (transpiration pull), it pulls the continuous column of water up the xylem [1]. This creates tension in the xylem vessels. [1]
(c) Some water is used for photosynthesis / maintaining turgor pressure / cell growth [1]. Therefore, not all water taken up is lost via transpiration. [1]
10.
(a) Transport of organic nutrients (sucrose/amino acids) from source to sink. [1]
(b) Xylem vessels are dead, hollow tubes with lignified walls [1]. Phloem sieve tubes are living cells with sieve plates and companion cells [1]. Xylem transports water/minerals; Phloem transports food. [1]
11.
(a) Nitrates are needed to make amino acids / proteins / chlorophyll. [1]
(b) Waterlogged soil has no air spaces / lacks oxygen [1]. Root cells cannot perform aerobic respiration [1]. They switch to anaerobic respiration which produces less energy / toxic ethanol, leading to cell death. [1]
12.
(a) Spongy mesophyll. [1]
(b) Large air spaces allow for rapid diffusion of gases (CO2 and O2) [1]. This ensures a constant supply of CO2 to the palisade cells for photosynthesis. [1]
13.
(a) Rate of transpiration increases. [1]
(b) Wind blows away water vapor accumulating near the leaf surface [1]. This maintains a steep concentration gradient of water vapor between the inside of the leaf and the outside air [1]. Faster diffusion of water vapor out of the stomata occurs. [1]
14.
| Feature | Cuticle | Stomata |
|---|---|---|
| Main Function | Reduce water loss / Protection | Gas exchange / Transpiration |
| Permeability to Water | Impermeable | Permeable (when open) |
[1] for each correct cell. Total [4].
15.
Photosynthesis produces glucose/organic food [1]. Heterotrophs (animals/fungi) eat plants or other animals to obtain this energy [1]. Photosynthesis also releases oxygen [1], which is required for aerobic respiration in most living organisms. [1] (Any 3 points)
Section C: Free Response Answers
16.
Water enters the root hair cell by osmosis because the cell sap has a lower water potential than the soil water [1]. Water moves across the cortex cells via the symplast pathway (through cytoplasm/plasmodesmata) or apoplast pathway (cell walls) [1]. At the endodermis, the Casparian strip forces water into the symplast to control entry [1]. Water enters the xylem vessels by osmosis/active transport of ions, creating a water potential gradient. [1]
17.
In light, potassium ions () are actively pumped into the guard cells from surrounding epidermal cells [1]. This lowers the water potential inside the guard cells [1]. Water enters the guard cells by osmosis [1]. The guard cells become turgid. Because the inner cell wall is thicker than the outer wall, they curve outward, opening the stomatal pore. [1]
18.
(a) The plant cells will lose water and become plasmolyzed [1]. The cytoplasm pulls away from the cell wall. [1]
(b) The salt solution has a lower water potential than the cell sap [1]. Water moves out of the cell by osmosis [1], down the water potential gradient, across the partially permeable cell membrane. [1]
19.
Benefit 1: Cools the plant / prevents overheating via evaporation. [1]
Benefit 2: Creates transpiration pull to transport water and mineral ions from roots to leaves. [1]
Disadvantage: Can lead to wilting / water deficit if water loss exceeds uptake, potentially killing the plant. [1]
(Explanation of any point for 4th mark) [1]
20.
- Thin/Transparent Upper Epidermis: Allows maximum light penetration to palisade cells. [1]
- Palisade Mesophyll: Packed with chloroplasts and arranged vertically to absorb maximum light. [1]
- Spongy Mesophyll: Air spaces facilitate rapid diffusion of CO2 to photosynthetic cells. [1]
- Stomata: Allow entry of CO2 and exit of O2. [1]
- Vascular Bundles (Xylem): Bring water to the leaf cells for photosynthesis. [1]
(Any 5 distinct adaptations with explanations)