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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: ______ / 50
Duration: 45 minutes
Total Marks: 50
Instructions:
- This quiz contains 20 questions on Plant Biology.
- Answer ALL questions in the spaces provided.
- The number of marks is given in brackets [ ] at the end of each question or part question.
- Show your working for calculation questions.
- You may use a calculator.
Section A: Short Answer (10 marks)
Answer all questions in this section.
1. Name the tissue in flowering plants responsible for transporting water and dissolved mineral salts from the roots to the leaves. [1]
2. State the word equation for photosynthesis. [2]
3. Name the pores found mainly on the lower epidermis of leaves that allow gas exchange. [1]
4. State two environmental factors that affect the rate of transpiration. [2]
5. Name the process by which dissolved food substances (sucrose and amino acids) are transported in the phloem. [1]
Section B: Structured Questions (15 marks)
Answer all questions in this section.
6. Identify the type of plant cell shown below that is adapted for absorbing water and mineral ions from the soil. [1]
7. State two uses of water in a flowering plant. [2]
8. Fig. 8.1 shows a cross-section of a dicotyledonous leaf.
(a) Identify the tissues labelled P, Q, and R. [3]
(b) Explain how the structure of tissue P is adapted for photosynthesis. [2]
(c) Explain why most stomata are found on the lower epidermis of the leaf. [2]
9. A student investigated the effect of light intensity on the rate of photosynthesis in an aquatic plant. The student counted the number of oxygen bubbles produced per minute at different distances from a lamp. The results are shown in Table 9.1.
Table 9.1
| Distance from lamp (cm) | Number of bubbles per minute |
|---|---|
| 10 | 45 |
| 20 | 32 |
| 30 | 20 |
| 40 | 12 |
| 50 | 8 |
(a) Describe the relationship between the distance from the lamp and the number of bubbles produced per minute. [2]
(b) Explain why the rate of photosynthesis decreases as the distance from the lamp increases. [2]
(c) State one variable, other than light intensity, that must be kept constant in this investigation. [1]
Section C: Structured Questions (15 marks)
Answer all questions in this section.
10. Suggest why the student used an aquatic plant rather than a terrestrial plant for this investigation. [1]
11. Fig. 11.1 shows the effect of carbon dioxide concentration on the rate of photosynthesis at two different light intensities.
(a) Explain why the rate of photosynthesis increases from point A to point B on the graph for high light intensity. [2]
(b) Explain why the rate of photosynthesis does not increase beyond point C for low light intensity. [2]
(c) State what must be increased for the rate of photosynthesis to increase beyond point C. [1]
12. A student used a potometer to measure the rate of water uptake by a leafy shoot under different environmental conditions. The air bubble moved 36 mm along a capillary tube of cross-sectional area 0.4 mm² in 15 minutes.
(a) Calculate the rate of water uptake in mm³ per minute. Show your working. [2]
(b) Explain why the potometer measures water uptake rather than the actual rate of transpiration. [2]
(c) State one precaution the student should take when setting up the potometer to ensure valid results. [1]
13. Fig. 13.1 shows the rate of transpiration and the rate of water absorption by a plant over a 24-hour period.
(a) State the time at which the rate of transpiration is at its maximum. [1]
(b) Describe what happens to the plant between 12:00 and 16:00 hours. Explain your answer with reference to the data. [3]
(c) Explain why the rate of transpiration is very low between 00:00 and 04:00 hours. [2]
Section D: Data Analysis and Extended Response (10 marks)
Answer all questions in this section.
14. Explain why most living organisms depend on photosynthesis for their survival. [4]
15. A farmer grows tomatoes in a greenhouse. During winter, the farmer adds extra carbon dioxide to the greenhouse and uses artificial lighting.
(a) Explain how adding extra carbon dioxide increases the yield of tomatoes. [2]
(b) Explain why the farmer must also ensure the greenhouse temperature is not too high, even though photosynthesis increases with temperature. [3]
16. Describe the pathway of water from the soil into the root and its transport to the leaf. [4]
17. Explain how the structure of xylem vessels is adapted for their function. [3]
18. Compare the roles of xylem and phloem in a flowering plant. [3]
19. Explain how wilting occurs in a plant and how it can recover. [3]
20. Discuss the importance of transpiration in plants. [3]
END OF QUIZ
Answers
Secondary 4 Pure Biology Quiz – Plant Biology
Answer Key and Marking Scheme
Total Marks: 50
Section A: Short Answer (10 marks)
1. Name the tissue in flowering plants responsible for transporting water and dissolved mineral salts from the roots to the leaves. [1]
Answer: Xylem (vessels) / Xylem tissue
Marking note: Accept "xylem" or "xylem vessels". Do not accept "phloem".
2. State the word equation for photosynthesis. [2]
Answer: Carbon dioxide + Water → Glucose + Oxygen (in the presence of light and chlorophyll)
Marking note: Award 1 mark for correct reactants (carbon dioxide and water), 1 mark for correct products (glucose and oxygen). Accept "light energy" or "sunlight" above/below the arrow. Do not penalise if "chlorophyll" is omitted but it is good practice to include it.
3. Name the pores found mainly on the lower epidermis of leaves that allow gas exchange. [1]
Answer: Stomata (singular: stoma)
Marking note: Accept "stomata" or "stoma". Do not accept "guard cells" (these are the cells surrounding the pore).
4. State two environmental factors that affect the rate of transpiration. [2]
Answer: Any two from:
- Light intensity
- Temperature
- Humidity (or water vapour concentration in the air)
- Wind speed / air movement
Marking note: Award 1 mark for each correct factor. Do not accept "water availability" (this affects absorption, not transpiration rate directly).
5. Name the process by which dissolved food substances (sucrose and amino acids) are transported in the phloem. [1]
Answer: Translocation
Marking note: Accept "translocation" only. Do not accept "transpiration" or "transpiration stream".
Section B: Structured Questions (15 marks)
6. Identify the type of plant cell shown below that is adapted for absorbing water and mineral ions from the soil. [1]
Answer: Root hair cell
Marking note: Accept "root hair cell". Do not accept "root cell" alone or "epidermal cell".
7. State two uses of water in a flowering plant. [2]
Answer: Any two from:
- Photosynthesis (raw material)
- Maintaining turgor pressure / turgidity of cells (support)
- Transport of dissolved mineral salts / ions
- Cooling the plant (by evaporation during transpiration)
- Cell elongation / growth
- Medium for chemical reactions
Marking note: Award 1 mark for each correct use. Answers must be distinct uses.
8. Fig. 8.1 shows a cross-section of a dicotyledonous leaf.
(a) Identify the tissues labelled P, Q, and R. [3]
Answer:
- P: Palisade mesophyll (tissue/cells)
- Q: Spongy mesophyll (tissue/cells)
- R: Xylem (vessel)
Marking note: Award 1 mark for each correct identification. Accept "palisade layer" for P, "spongy layer" for Q. For R, accept "vascular bundle" or "vein" but "xylem" is the specific tissue transporting water.
(b) Explain how the structure of tissue P is adapted for photosynthesis. [2]
Answer: Palisade mesophyll cells are elongated/columnar and closely packed. They contain many chloroplasts to maximise light absorption. They are located near the upper epidermis where light intensity is highest.
Marking note: Award 1 mark for "many chloroplasts" or "contains chloroplasts", and 1 mark for "near upper epidermis / near leaf surface to absorb maximum light" or "elongated/close-packed for maximum light capture". Must link structure to function.
(c) Explain why most stomata are found on the lower epidermis of the leaf. [2]
Answer: The lower epidermis is not directly exposed to sunlight, so it is cooler than the upper epidermis. This reduces the rate of evaporation of water from the leaf, thereby reducing water loss by transpiration. Having stomata on the lower surface also reduces direct exposure to wind, which would increase transpiration.
Marking note: Award 1 mark for "cooler / less exposed to sun" and 1 mark for "reduces water loss / reduces transpiration". Accept references to reduced concentration gradient or reduced evaporation.
9. A student investigated the effect of light intensity on the rate of photosynthesis in an aquatic plant.
(a) Describe the relationship between the distance from the lamp and the number of bubbles produced per minute. [2]
Answer: As the distance from the lamp increases, the number of bubbles produced per minute decreases. The decrease is not linear; the rate drops more sharply at closer distances and more gradually at greater distances.
Marking note: Award 1 mark for stating the inverse relationship (distance increases, bubbles decrease). Award 1 mark for noting the non-linear nature or describing the pattern (e.g., "from 10 cm to 20 cm the decrease is 13 bubbles/min, but from 40 cm to 50 cm the decrease is only 4 bubbles/min").
(b) Explain why the rate of photosynthesis decreases as the distance from the lamp increases. [2]
Answer: As distance from the lamp increases, light intensity decreases (light spreads out over a larger area). With lower light intensity, less light energy is available for the light-dependent reactions of photosynthesis. Therefore, less ATP and NADPH are produced, and the rate of the Calvin cycle (light-independent reactions) decreases, reducing the overall rate of photosynthesis.
Marking note: Award 1 mark for linking increased distance to decreased light intensity. Award 1 mark for explaining that less light energy reduces photosynthesis rate (reference to light-dependent reactions or ATP/NADPH production).
(c) State one variable, other than light intensity, that must be kept constant in this investigation. [1]
Answer: Any one from:
- Carbon dioxide concentration
- Temperature
- Type/species of aquatic plant
- Size/age of aquatic plant
- Volume of water
- pH of water
Marking note: Award 1 mark for any valid controlled variable. Do not accept "light intensity" (this is the independent variable) or "number of bubbles" (this is the dependent variable).
Section C: Structured Questions (15 marks)
10. Suggest why the student used an aquatic plant rather than a terrestrial plant for this investigation. [1]
Answer: An aquatic plant produces oxygen bubbles that can be easily seen and counted, providing a direct and measurable indication of the rate of photosynthesis. In a terrestrial plant, gas exchange is not as easily observed or quantified.
Marking note: Award 1 mark for the idea that oxygen bubbles are visible/easily counted in water. Accept "oxygen produced can be collected and measured" or "bubbles indicate rate of photosynthesis".
11. Fig. 11.1 shows the effect of carbon dioxide concentration on the rate of photosynthesis at two different light intensities.
(a) Explain why the rate of photosynthesis increases from point A to point B on the graph for high light intensity. [2]
Answer: From A to B, carbon dioxide concentration is the limiting factor. As CO₂ concentration increases, more CO₂ is available for the Calvin cycle (light-independent reactions). This allows more glucose to be produced, so the rate of photosynthesis increases. Light intensity is not limiting because it is high.
Marking note: Award 1 mark for identifying CO₂ as the limiting factor. Award 1 mark for explaining that more CO₂ allows more photosynthesis (reference to Calvin cycle or carbon fixation).
(b) Explain why the rate of photosynthesis does not increase beyond point C for low light intensity. [2]
Answer: Beyond point C, light intensity has become the limiting factor. Although CO₂ concentration continues to increase, the low light intensity means that the light-dependent reactions cannot produce enough ATP and NADPH to support a higher rate in the Calvin cycle. Therefore, increasing CO₂ alone cannot increase the rate of photosynthesis.
Marking note: Award 1 mark for identifying light intensity as the limiting factor. Award 1 mark for explaining that low light limits ATP/NADPH production, restricting the Calvin cycle.
(c) State what must be increased for the rate of photosynthesis to increase beyond point C. [1]
Answer: Light intensity
Marking note: Accept "light intensity" only.
12. A student used a potometer to measure the rate of water uptake by a leafy shoot under different environmental conditions. The air bubble moved 36 mm along a capillary tube of cross-sectional area 0.4 mm² in 15 minutes.
(a) Calculate the rate of water uptake in mm³ per minute. Show your working. [2]
Answer: Volume = distance × cross-sectional area = 36 mm × 0.4 mm² = 14.4 mm³. Rate = volume / time = 14.4 mm³ / 15 min = 0.96 mm³ per minute.
Marking note: Award 1 mark for correct calculation of volume (14.4 mm³). Award 1 mark for correct rate (0.96 mm³/min). Accept equivalent working.
(b) Explain why the potometer measures water uptake rather than the actual rate of transpiration. [2]
Answer: The potometer measures the volume of water taken up by the shoot. Some of this water is used in photosynthesis and other metabolic processes, and some may be stored in the plant cells. Therefore, the water uptake is slightly greater than the water lost by transpiration.
Marking note: Award 1 mark for stating that not all water taken up is lost by transpiration. Award 1 mark for giving a reason (e.g., used in photosynthesis, stored in cells).
(c) State one precaution the student should take when setting up the potometer to ensure valid results. [1]
Answer: Any one from:
- Ensure the shoot is cut under water to prevent air bubbles entering the xylem.
- Ensure all joints are airtight/watertight (sealed with petroleum jelly).
- Ensure the capillary tube is dry before introducing the air bubble.
- Use a healthy, leafy shoot.
- Allow the plant time to acclimatise before taking measurements.
Marking note: Award 1 mark for any valid precaution.
13. Fig. 13.1 shows the rate of transpiration and the rate of water absorption by a plant over a 24-hour period.
(a) State the time at which the rate of transpiration is at its maximum. [1]
Answer: 12:00 (hours) / noon / midday
Marking note: Accept any clear indication of 12:00.
(b) Describe what happens to the plant between 12:00 and 16:00 hours. Explain your answer with reference to the data. [3]
Answer: Between 12:00 and 16:00, the rate of transpiration exceeds the rate of water absorption. This means the plant is losing water faster than it is taking it up. As a result, the plant cells lose turgor pressure, and the plant may wilt. The stomata may also begin to close to reduce water loss.
Marking note: Award 1 mark for stating transpiration rate > absorption rate. Award 1 mark for explaining the consequence (water deficit, loss of turgor, wilting). Award 1 mark for reference to data (e.g., transpiration line is above absorption line).
(c) Explain why the rate of transpiration is very low between 00:00 and 04:00 hours. [2]
Answer: During this period, it is dark (no light). The stomata are closed in the dark, which prevents water vapour from diffusing out of the leaf. Additionally, the temperature is usually lower at night, which reduces the rate of evaporation of water.
Marking note: Award 1 mark for stomata closed due to darkness. Award 1 mark for lower temperature reducing evaporation. Accept references to reduced wind or higher humidity at night.
Section D: Data Analysis and Extended Response (10 marks)
14. Explain why most living organisms depend on photosynthesis for their survival. [4]
Answer: Photosynthesis produces glucose, which is a source of chemical potential energy. Plants use this glucose for respiration to release energy for their life processes. Animals obtain energy by eating plants (herbivores) or by eating other animals that have eaten plants (carnivores). Therefore, photosynthesis is the primary source of energy for almost all food chains. Additionally, photosynthesis produces oxygen, which is essential for aerobic respiration in most living organisms, including plants and animals. Oxygen is used to break down glucose to release energy efficiently.
Marking note: Award 1 mark for producing glucose/chemical energy. Award 1 mark for being the basis of food chains/energy source for consumers. Award 1 mark for producing oxygen. Award 1 mark for oxygen being essential for aerobic respiration.
15. A farmer grows tomatoes in a greenhouse. During winter, the farmer adds extra carbon dioxide to the greenhouse and uses artificial lighting.
(a) Explain how adding extra carbon dioxide increases the yield of tomatoes. [2]
Answer: Carbon dioxide is a raw material for photosynthesis. By increasing the carbon dioxide concentration, the rate of photosynthesis increases (as long as other factors are not limiting). This results in more glucose being produced, which can be used for growth and fruit development, thus increasing the yield of tomatoes.
Marking note: Award 1 mark for CO₂ as a raw material for photosynthesis. Award 1 mark for linking increased photosynthesis to increased growth/yield.
(b) Explain why the farmer must also ensure the greenhouse temperature is not too high, even though photosynthesis increases with temperature. [3]
Answer: Photosynthesis is controlled by enzymes. As temperature increases, enzyme activity increases, so the rate of photosynthesis increases up to an optimum temperature. However, if the temperature becomes too high (above the optimum), the enzymes denature. The active site of the enzyme changes shape, so the substrate can no longer bind, and the rate of photosynthesis decreases sharply. This would reduce the yield. Also, very high temperatures increase the rate of transpiration, which could lead to excessive water loss and wilting.
Marking note: Award 1 mark for enzymes controlling photosynthesis. Award 1 mark for denaturation at high temperatures (loss of active site shape). Award 1 mark for consequence (photosynthesis stops/decreases, or excessive water loss).
16. Describe the pathway of water from the soil into the root and its transport to the leaf. [4]
Answer: Water enters the root hair cells from the soil by osmosis, as the water potential in the soil is higher than in the root hair cell. The water then moves from cell to cell across the root cortex (via the apoplast, symplast, or vacuolar pathways) until it reaches the endodermis. The Casparian strip in the endodermis blocks the apoplast pathway, forcing water into the symplast. Water then enters the xylem vessels in the vascular bundle. From the roots, water is transported up the stem through the xylem vessels to the leaves. This upward movement is driven by transpiration pull (cohesion-tension theory), where water evaporates from the leaves, creating a tension that pulls the water column up.
Marking note: Award 1 mark for entry by osmosis into root hair cells. Award 1 mark for movement across the cortex to the xylem. Award 1 mark for transport in xylem vessels. Award 1 mark for transpiration pull/cohesion-tension.
17. Explain how the structure of xylem vessels is adapted for their function. [3]
Answer: Xylem vessels are long, continuous, hollow tubes formed from dead cells with no end walls. This allows for unimpeded flow of water and dissolved mineral salts. The walls are thickened with lignin, which provides mechanical strength and prevents the vessels from collapsing under the tension created by transpiration. The lignin is deposited in rings, spirals, or pits, which allows some flexibility and lateral movement of water.
Marking note: Award 1 mark for hollow tubes/no end walls (continuous column). Award 1 mark for lignified walls (strength/prevent collapse). Award 1 mark for pits or flexibility.
18. Compare the roles of xylem and phloem in a flowering plant. [3]
Answer: Xylem transports water and dissolved mineral salts from the roots to the stems and leaves. This transport is unidirectional (upwards). Phloem transports dissolved food substances (sucrose and amino acids) from the leaves (source) to other parts of the plant (sinks) such as roots, fruits, and growing tips. This transport is bidirectional. Xylem also provides mechanical support to the plant due to lignified walls, whereas phloem does not have a primary support function.
Marking note: Award 1 mark for xylem transporting water/minerals upwards. Award 1 mark for phloem transporting food/sucrose bidirectionally. Award 1 mark for any other valid comparison (e.g., support, direction, composition).
19. Explain how wilting occurs in a plant and how it can recover. [3]
Answer: Wilting occurs when the rate of transpiration (water loss) exceeds the rate of water absorption from the soil. This causes a water deficit in the plant cells, leading to a loss of turgor pressure. The cells become flaccid, and the non-woody parts of the plant (leaves and stems) droop. The plant can recover if water becomes available again. Water is absorbed by the roots, and the cells regain turgor pressure, causing the plant to become turgid and upright again. Wilting itself is a protective mechanism, as the drooping leaves reduce the surface area exposed to sunlight and wind, thereby reducing further water loss.
Marking note: Award 1 mark for water loss > water uptake. Award 1 mark for loss of turgor pressure/flaccidity. Award 1 mark for recovery by water uptake/regaining turgor.
20. Discuss the importance of transpiration in plants. [3]
Answer: Transpiration is the loss of water vapour from the aerial parts of the plant, mainly through the stomata. It creates a transpiration pull, which draws water and dissolved mineral salts up the xylem from the roots to the leaves. This is essential for transporting minerals needed for growth and metabolism. Transpiration also helps to cool the plant by evaporative cooling, preventing overheating in strong sunlight. Additionally, it maintains the turgidity of cells, which is important for support and cell expansion.
Marking note: Award 1 mark for transport of water and minerals. Award 1 mark for cooling effect. Award 1 mark for maintaining turgidity/support.
END OF ANSWER KEY