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Secondary 4 Combined Science Biology Plant Biology Quiz
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Questions
Secondary 4 Combined Science Biology Quiz - Plant Biology
Name: _________________________ Class: _________________________ Date: _________________________ Score: ______ / 40
Duration: 45 minutes Total Marks: 40
Instructions:
- This quiz contains 20 questions on Plant Biology.
- Answer ALL questions in the spaces provided.
- The number of marks for each question is shown in brackets.
- Show your working where appropriate.
- Use scientific terminology accurately.
Section A: Short Answer (10 marks)
Answer all questions in this section.
1. State the word equation for photosynthesis.
_____________________________________________________________________________ [1]
2. Name the green pigment found in chloroplasts that absorbs light energy for photosynthesis. _____________________________________________________________________________ [1]
3. State ONE structural adaptation of a xylem vessel that allows efficient transport of water. _____________________________________________________________________________ [1]
4. Name the process by which water vapour is lost from the aerial parts of a plant. _____________________________________________________________________________ [1]
5. Identify the tissue responsible for transporting sucrose and amino acids from leaves to other parts of the plant. _____________________________________________________________________________ [1]
Section B: Short Answer (10 marks)
Answer all questions in this section.
6. State the function of stomata in a leaf. _____________________________________________________________________________ [1]
7. Name the waxy layer on the upper surface of a leaf that reduces water loss. _____________________________________________________________________________ [1]
8. State ONE condition under which the rate of transpiration would increase. _____________________________________________________________________________ [1]
9. Name the carbohydrate that is the main product of photosynthesis and is transported in the phloem. _____________________________________________________________________________ [1]
10. Identify the part of a flower that receives pollen grains during pollination. _____________________________________________________________________________ [1]
Section C: Structured Questions (10 marks)
Answer all questions in this section.
11. 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.
| Distance from lamp (cm) | Number of bubbles per minute |
|---|---|
| 10 | 45 |
| 20 | 32 |
| 30 | 18 |
| 40 | 8 |
| 50 | 2 |
(a) Describe the relationship between distance from the lamp and the number of bubbles produced per minute.
_____________________________________________________________________________ [1]
(b) Explain why the number of bubbles decreases as the distance from the lamp increases.
_____________________________________________________________________________ [2]
(c) Suggest ONE other factor, apart from light intensity, that the student should keep constant during this investigation. _____________________________________________________________________________ [1]
12. The diagram below shows a cross-section of a leaf.
(Diagram shows: upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis, stomata, air spaces)
(a) Explain why palisade mesophyll cells contain more chloroplasts than spongy mesophyll cells.
_____________________________________________________________________________ [2]
(b) Describe the function of the air spaces in the spongy mesophyll layer.
_____________________________________________________________________________ [1]
(c) Explain how the structure of a palisade mesophyll cell is adapted for photosynthesis.
_____________________________________________________________________________ [2]
13. A potometer was used to measure the rate of water uptake by a leafy shoot under different environmental conditions. The results are shown below.
| Condition | Distance bubble moved in 10 minutes (mm) |
|---|---|
| Still air | 24 |
| Moving air (fan) | 56 |
| Humid air | 12 |
(a) Explain why the rate of water uptake is higher in moving air compared to still air.
_____________________________________________________________________________ [2]
(b) Explain why the rate of water uptake is lower in humid air.
_____________________________________________________________________________ [1]
(c) State ONE precaution the student should take when setting up the potometer to ensure accurate results. _____________________________________________________________________________ [1]
Section D: Data Analysis and Extended Response (10 marks)
Answer all questions in this section.
14. A student placed a strip of potato in a concentrated sugar solution for 30 minutes. After 30 minutes, the potato strip became soft and flaccid.
(a) Name the process that caused the potato strip to become flaccid. _____________________________________________________________________________ [1]
(b) Explain why the potato strip became flaccid in the concentrated sugar solution.
_____________________________________________________________________________ [2]
(c) Describe what would happen to a plant cell if it were placed in distilled water.
_____________________________________________________________________________ [1]
15. The graph below shows the effect of carbon dioxide concentration on the rate of photosynthesis at two different light intensities.
(Graph description: Rate of photosynthesis on y-axis, CO₂ concentration on x-axis. Two curves: Curve A at high light intensity, Curve B at low light intensity. Curve A rises steeply then plateaus at point X. Curve B rises slowly and plateaus at a lower rate.)
(a) Identify the limiting factor at point X on Curve A. Explain your answer.
_____________________________________________________________________________ [2]
(b) Explain why Curve B plateaus at a lower rate of photosynthesis than Curve A.
_____________________________________________________________________________ [1]
(c) A farmer wants to increase the yield of crops in a greenhouse. Suggest and explain TWO ways the farmer could increase the rate of photosynthesis.
_____________________________________________________________________________ [4]
16. In some species of flowering plants, the anthers produce pollen before the stigma of the same flower is mature and ready to receive pollen. By the time the stigma is receptive, the anthers have stopped producing pollen.
(a) Suggest why this timing mechanism is advantageous to the plant.
_____________________________________________________________________________ [1]
(b) Explain how cross-pollination increases genetic variation within a plant population.
_____________________________________________________________________________ [2]
(c) State ONE structural adaptation of an insect-pollinated flower that differs from a wind-pollinated flower, and explain how this adaptation aids pollination.
_____________________________________________________________________________ [2]
17. Describe the pathway of water from the soil into the root hair cell, and then through the root to the xylem.
_____________________________________________________________________________ [2]
18. Explain why a plant wilts when it loses more water by transpiration than it absorbs from the soil.
_____________________________________________________________________________ [2]
19. Compare the structure and function of xylem and phloem tissues in flowering plants.
_____________________________________________________________________________ [2]
20. Discuss the importance of photosynthesis to life on Earth.
_____________________________________________________________________________ [2]
END OF QUIZ
Answers
Secondary 4 Combined Science Biology Quiz - Plant Biology
Answer Key and Marking Scheme
Total Marks: 40
Section A: Short Answer (10 marks)
1. State the word equation for photosynthesis. [1]
- Answer: Carbon dioxide + water → glucose + oxygen (in the presence of light and chlorophyll)
- Marking: Award 1 mark for correct reactants and products. Accept "light energy" or "sunlight" above the arrow. Do not penalise if "chlorophyll" is written above the arrow.
2. Name the green pigment found in chloroplasts that absorbs light energy for photosynthesis. [1]
- Answer: Chlorophyll
- Marking: Award 1 mark for "chlorophyll" only.
3. State ONE structural adaptation of a xylem vessel that allows efficient transport of water. [1]
- Answer: Hollow tube with no cytoplasm / no cross-walls / walls thickened with lignin (any one)
- Marking: Award 1 mark for any one correct adaptation.
4. Name the process by which water vapour is lost from the aerial parts of a plant. [1]
- Answer: Transpiration
- Marking: Award 1 mark for "transpiration" only.
5. Identify the tissue responsible for transporting sucrose and amino acids from leaves to other parts of the plant. [1]
- Answer: Phloem
- Marking: Award 1 mark for "phloem" only.
Section B: Short Answer (10 marks)
6. State the function of stomata in a leaf. [1]
- Answer: Allow gas exchange (carbon dioxide in, oxygen out) / allow transpiration (water vapour out) (any one)
- Marking: Award 1 mark for any one correct function.
7. Name the waxy layer on the upper surface of a leaf that reduces water loss. [1]
- Answer: Cuticle
- Marking: Award 1 mark for "cuticle" only.
8. State ONE condition under which the rate of transpiration would increase. [1]
- Answer: Increased temperature / increased wind speed / decreased humidity / increased light intensity (any one)
- Marking: Award 1 mark for any one correct condition.
9. Name the carbohydrate that is the main product of photosynthesis and is transported in the phloem. [1]
- Answer: Sucrose
- Marking: Award 1 mark for "sucrose" only. Do not accept "glucose".
10. Identify the part of a flower that receives pollen grains during pollination. [1]
- Answer: Stigma
- Marking: Award 1 mark for "stigma" only.
Section C: Structured Questions (10 marks)
11. [4 marks]
(a) Describe the relationship between distance from the lamp and the number of bubbles produced per minute. [1]
- Answer: As the distance from the lamp increases, the number of bubbles produced per minute decreases.
- Marking: Award 1 mark for correct relationship (inverse relationship).
(b) Explain why the number of bubbles decreases as the distance from the lamp increases. [2]
- Answer: As distance increases, light intensity decreases. Lower light intensity means less light energy is available for photosynthesis, so the rate of photosynthesis decreases, producing less oxygen (fewer bubbles).
- Marking: Award 1 mark for linking distance to decreased light intensity. Award 1 mark for linking decreased light intensity to lower rate of photosynthesis/oxygen production.
(c) Suggest ONE other factor, apart from light intensity, that the student should keep constant during this investigation. [1]
- Answer: Temperature / carbon dioxide concentration / type of plant / number of leaves / volume of water (any one)
- Marking: Award 1 mark for any one valid controlled variable.
12. [5 marks]
(a) Explain why palisade mesophyll cells contain more chloroplasts than spongy mesophyll cells. [2]
- Answer: Palisade mesophyll cells are located near the upper surface of the leaf and receive more direct light. More chloroplasts allow maximum absorption of light energy for photosynthesis. Spongy mesophyll cells receive less light, so fewer chloroplasts are needed.
- Marking: Award 1 mark for identifying that palisade cells receive more light. Award 1 mark for linking more chloroplasts to increased light absorption/photosynthesis.
(b) Describe the function of the air spaces in the spongy mesophyll layer. [1]
- Answer: Allow rapid diffusion of gases (carbon dioxide and oxygen) throughout the leaf / provide a large surface area for gas exchange.
- Marking: Award 1 mark for gas exchange or diffusion of gases.
(c) Explain how the structure of a palisade mesophyll cell is adapted for photosynthesis. [2]
- Answer: Palisade cells are elongated and closely packed, containing many chloroplasts to maximise light absorption. The chloroplasts can move within the cell to position themselves for optimal light capture. The cells are arranged vertically to allow more cells to fit near the leaf surface.
- Marking: Award 1 mark for mentioning many chloroplasts/elongated shape. Award 1 mark for linking structure to increased light absorption/photosynthesis. Accept any two valid adaptations with explanations.
13. [4 marks]
(a) Explain why the rate of water uptake is higher in moving air compared to still air. [2]
- Answer: Moving air (wind) removes water vapour from around the stomata. This maintains a steep concentration gradient of water vapour between the leaf's internal air spaces and the external environment. Water vapour diffuses out faster, increasing the transpiration rate, so more water is pulled up the xylem.
- Marking: Award 1 mark for mentioning removal of water vapour/maintaining concentration gradient. Award 1 mark for linking to increased transpiration/water uptake.
(b) Explain why the rate of water uptake is lower in humid air. [1]
- Answer: Humid air has a high concentration of water vapour, reducing the concentration gradient between the leaf and the external environment. This slows down the diffusion of water vapour out of the leaf, reducing transpiration.
- Marking: Award 1 mark for mentioning reduced concentration gradient or slower diffusion.
(c) State ONE precaution the student should take when setting up the potometer to ensure accurate results. [1]
- Answer: Ensure all connections are airtight / cut the stem under water to prevent air bubbles entering xylem / ensure no air bubbles in the apparatus / use a healthy leafy shoot (any one)
- Marking: Award 1 mark for any one valid precaution.
Section D: Data Analysis and Extended Response (10 marks)
14. [4 marks]
(a) Name the process that caused the potato strip to become flaccid. [1]
- Answer: Osmosis
- Marking: Award 1 mark for "osmosis" only.
(b) Explain why the potato strip became flaccid in the concentrated sugar solution. [2]
- Answer: The concentrated sugar solution has a lower water potential than the potato cells. Water moves out of the potato cells by osmosis, from a region of higher water potential (inside cells) to lower water potential (sugar solution), through a partially permeable membrane. The cells lose water, become plasmolysed, and the potato strip becomes flaccid.
- Marking: Award 1 mark for identifying water potential difference and direction of water movement. Award 1 mark for linking water loss to flaccidity/plasmolysis.
(c) Describe what would happen to a plant cell if it were placed in distilled water. [1]
- Answer: Water would enter the cell by osmosis. The cell would become turgid (swollen) but would not burst because the cell wall prevents over-expansion.
- Marking: Award 1 mark for turgid or swollen with reference to cell wall preventing bursting.
15. [7 marks]
(a) Identify the limiting factor at point X on Curve A. Explain your answer. [2]
- Answer: Carbon dioxide concentration is no longer the limiting factor. At point X, the rate of photosynthesis has plateaued despite increasing CO₂ concentration. The limiting factor is now light intensity (or temperature). This is shown because Curve A (high light intensity) plateaus at a higher rate than Curve B (low light intensity).
- Marking: Award 1 mark for identifying that CO₂ is no longer limiting. Award 1 mark for identifying light intensity (or temperature) as the new limiting factor with reference to the plateau.
(b) Explain why Curve B plateaus at a lower rate of photosynthesis than Curve A. [1]
- Answer: Curve B is at a lower light intensity. Light intensity is the limiting factor, so even with increasing CO₂ concentration, the rate of photosynthesis cannot exceed the maximum rate possible at that lower light intensity.
- Marking: Award 1 mark for identifying light intensity as the limiting factor for Curve B.
(c) A farmer wants to increase the yield of crops in a greenhouse. Suggest and explain TWO ways the farmer could increase the rate of photosynthesis. [4]
- Answer: 1. Increase light intensity using artificial lighting. This provides more light energy for the light-dependent reactions of photosynthesis, increasing the rate. 2. Increase carbon dioxide concentration by burning fuel or using a CO₂ generator. CO₂ is a reactant in photosynthesis, so a higher concentration increases the rate of the light-independent reactions. 3. Increase temperature (within optimal range) using heaters. This increases the kinetic energy of molecules, leading to more frequent collisions between enzymes and substrates, increasing the rate of photosynthetic reactions. (Accept any two valid suggestions with explanations.)
- Marking: For each suggestion, award 1 mark for a valid method and 1 mark for a correct explanation linked to photosynthesis. Maximum 4 marks.
16. [5 marks]
(a) Suggest why this timing mechanism is advantageous to the plant. [1]
- Answer: It promotes cross-pollination / prevents self-pollination, which increases genetic variation in the offspring.
- Marking: Award 1 mark for promoting cross-pollination or preventing self-pollination.
(b) Explain how cross-pollination increases genetic variation within a plant population. [2]
- Answer: Cross-pollination involves the fusion of gametes from two different plants. This combines genetic material from two different parents, resulting in offspring with new combinations of alleles. This increases the genetic diversity within the population.
- Marking: Award 1 mark for fusion of gametes from different plants. Award 1 mark for new combinations of alleles/increased genetic diversity.
(c) State ONE structural adaptation of an insect-pollinated flower that differs from a wind-pollinated flower, and explain how this adaptation aids pollination. [2]
- Answer: Large, brightly coloured petals. This attracts insects to the flower. When insects visit to feed on nectar, pollen grains stick to their bodies and are transferred to the stigma of another flower. (Accept other valid adaptations such as: sticky/spiny pollen grains that attach to insects; presence of nectaries to reward insects; stigma and anthers positioned inside the flower to ensure contact with the insect.)
- Marking: Award 1 mark for a correct structural adaptation. Award 1 mark for a correct explanation of how it aids insect pollination.
17. Describe the pathway of water from the soil into the root hair cell, and then through the root to the xylem. [2]
- Answer: Water enters the root hair cell from the soil by osmosis, moving from a region of higher water potential in the soil to a lower water potential in the root hair cell. Water then moves from cell to cell through the cortex of the root by osmosis, eventually reaching the xylem vessels in the centre of the root.
- Marking: Award 1 mark for osmosis from soil into root hair cell. Award 1 mark for movement through the cortex to the xylem.
18. Explain why a plant wilts when it loses more water by transpiration than it absorbs from the soil. [2]
- Answer: When water loss by transpiration exceeds water uptake from the soil, the plant cells lose water and become flaccid. The cells lose turgor pressure, causing the non-woody parts of the plant to become limp and droop.
- Marking: Award 1 mark for loss of water from cells/flaccidity. Award 1 mark for loss of turgor pressure causing wilting.
19. Compare the structure and function of xylem and phloem tissues in flowering plants. [2]
- Answer: Xylem is composed of dead, hollow tubes with lignified walls; its function is to transport water and dissolved mineral ions from the roots to the rest of the plant, and to provide structural support. Phloem is composed of living cells (sieve tubes and companion cells); its function is to transport sucrose and amino acids (translocation) from sources (e.g., leaves) to sinks (e.g., roots, fruits) in the plant.
- Marking: Award 1 mark for correct comparison of structure (e.g., dead vs. living, hollow tubes vs. sieve tubes). Award 1 mark for correct comparison of function (water/minerals transport vs. sucrose/amino acids transport).
20. Discuss the importance of photosynthesis to life on Earth. [2]
- Answer: Photosynthesis produces oxygen, which is essential for aerobic respiration in most living organisms. It also converts light energy into chemical energy stored in glucose, which forms the basis of most food chains, providing energy for nearly all life on Earth. Additionally, photosynthesis removes carbon dioxide from the atmosphere, helping to regulate the Earth's climate.
- Marking: Award 1 mark for oxygen production for respiration. Award 1 mark for energy/food source for ecosystems. Accept other valid points such as carbon dioxide removal.