SOF Olympiad Class 4 Science Chapter 1 MCQs
Master SOF Olympiad Class 4 Science Chapter 1 (Food Preparation in Plants) with 30 high-level practice MCQs, detailed answer keys, and explanations.
1. A student covered a portion of a healthy green leaf with black paper and left the plant in sunlight for 24 hours. After performing an iodine test, the covered portion stayed brown while the uncovered portion turned blue-black. What primary conclusion can be drawn from this experiment?
A. Sunlight is required for carbon dioxide absorption by stomata.
B. Sunlight is essential for the synthesis of starch in green leaves.
C. Starch is directly absorbed from sunlight by chlorophyll.
D. Chlorophyll turns blue-black in the presence of sunlight.
2. Which of the following correctly traces the path of water transport within a plant during photosynthesis?
A. Stomata → Leaf Blade → Midrib → Stalk → Roots
B. Roots → Stem → Stalk (Petiole) → Main Vein (Midrib) → Side Veins → Leaf Cells
C. Main Vein → Side Veins → Stalk → Stem → Roots
D. Roots → Stomata → Main Vein → Side Veins → Stem
3. Cactus plants thrive in arid desert environments where leaves are modified into spines. How do cactus plants manufacture their food?
A. They absorb pre-made organic food directly from desert soil through roots.
B. Their roots contain high levels of chlorophyll and perform photosynthesis underground.
C. Their fleshy green stems contain chlorophyll and perform photosynthesis.
D. They feed on insects trapped by their sharp, needle-like spines.
4. During an experiment, a student boiled a green leaf first in water and then in alcohol before applying iodine solution. What is the primary purpose of boiling the leaf in alcohol?
A. To soften the tough outer wall of the lamina
B. To dissolve and remove chlorophyll, making color changes clearly visible
C. To convert stored glucose back into active starch
D. To kill harmful bacteria present on the leaf surface
5. Consider the following food chain: Grass → Deer → Lion. Which statement correctly describes the flow of energy and materials in this system?
A. Energy flows from the lion to the deer, and ultimate energy comes from soil minerals.
B. The sun provides energy to grass; this solar energy passes sequentially to deer and lion.
C. Deer is a primary producer that converts grass into direct sunlight for lions.
D. Energy increases as it flows from grass to deer and then to the apex carnivore.
6. Stomata are microscopic openings located mostly on the underside of green leaves. What is their primary functional role in plant metabolism?
A. Absorbing liquid water and soil minerals directly from rain
B. Facilitating gaseous exchange (taking in CO₂ and releasing O₂) and transpiration
C. Anchoring the leaf firmly to the stem stalk
D. Storing excess starch produced during daytime photosynthesis
7. Mushrooms and toadstools are non-green organisms that lack chlorophyll. How do they obtain their essential nutrients?
A. They absorb sunlight directly through subterranean root-like hyphae.
B. They perform photosynthesis using atmospheric nitrogen instead of carbon dioxide.
C. They obtain nutrients by absorbing organic matter from dead and decaying organisms.
D. They trap tiny soil insects and digest them using leaf blade secretions.
8. In plant physiology, what immediate product is synthesized during photosynthesis, and in what form is extra food stored across plant tissues?
A. Immediate product: Starch | Stored form: Glucose
B. Immediate product: Glucose | Stored form: Starch
C. Immediate product: Oxygen | Stored form: Chlorophyll
D. Immediate product: Carbon Dioxide | Stored form: Protein
9. Match the edible plant part with its corresponding example:
1. Root 2. Stem 3. Leaf 4. Seed
P. Cabbage Q. Carrot R. Peas S. Sugar cane
A. 1-Q, 2-S, 3-P, 4-R
B. 1-P, 2-Q, 3-R, 4-S
C. 1-S, 2-R, 3-Q, 4-P
D. 1-Q, 2-P, 3-S, 4-R
10. What would be the most immediate environmental consequence if all green plants on Earth were to suddenly disappear?
A. Atmospheric oxygen levels would rapidly decrease while carbon dioxide levels would rise.
B. Atmospheric oxygen and carbon dioxide levels would both increase rapidly.
C. Soil water content would permanently double due to lack of absorption.
D. Non-green plants like mushrooms would rapidly populate the entire planet.
11. A potted plant was placed in a light-tight dark box for 72 hours before a photosynthesis experiment. What was the scientific purpose of keeping the plant in the dark?
A. To allow the plant to absorb maximum humidity from surrounding air
B. To completely destarch the leaves by utilizing all stored starch for survival
C. To permanently stop stomata from ever opening again
D. To stimulate the production of additional chlorophyll in the dark
12. Analyze the following statements about leaf structure:
Statement 1: The main vein (midrib) runs through the middle of the leaf blade.
Statement 2: Side veins carry water and minerals to all parts of the leaf and bring back prepared food.
Which of the following is correct?
A. Statement 1 is true, but Statement 2 is false.
B. Statement 1 is false, but Statement 2 is true.
C. Both Statement 1 and Statement 2 are true.
D. Both Statement 1 and Statement 2 are false.
13. Which annual environmental event celebrated in India encourages forest conservation and widespread tree planting to maintain ecological balance?
A. Swachh Bharat Abhiyan
B. Van Mahotsava
C. Jal Shakti Abhiyan
D. National Science Day
14. Why are leaves universally referred to as the ‘kitchen’ or ‘food factory’ of a plant?
A. Because they store water and minerals collected from the roots
B. Because they synthesize organic food (glucose) for the entire plant using raw materials
C. Because they protect flowers and fruits from harsh climatic conditions
D. Because they release excess heat to keep the plant cool during summer
15. A student tested four food items with iodine solution:
Item 1: Boiled rice | Item 2: Potato slice | Item 3: Cooking oil | Item 4: Sugar cube
Which items will produce a distinct blue-black color test result?
A. Items 1 and 2 only
B. Items 2 and 3 only
C. Items 1 and 4 only
D. Items 3 and 4 only
16. What critical role does chlorophyll play during the process of photosynthesis?
A. It absorbs water droplets directly from humid atmospheric air.
B. It captures and traps light energy from sunlight.
C. It breaks down soil minerals into oxygen gas.
D. It converts excess starch directly into glucose energy.
17. Which of the following chemical word equations accurately represents the process of photosynthesis?
A. Glucose + Oxygen + Sunlight → Carbon dioxide + Water
B. Carbon dioxide + Water + Sunlight (in presence of Chlorophyll) → Glucose + Oxygen
C. Oxygen + Water + Chlorophyll → Carbon dioxide + Glucose
D. Carbon dioxide + Starch + Sunlight → Water + Oxygen
18. In a classroom activity, Jyotsna covered her growing money plant pot completely with a light-proof wooden box. She watered it regularly for two weeks, but the plant withered and died. What was the cause?
A. Excess water accumulated in the soil without evaporation.
B. The plant could not perform photosynthesis without sunlight to produce food.
C. Money plants only survive on artificial room lighting.
D. Water blocked the roots from absorbing sunlight.
19. Which part of a leaf attaches the leaf blade (lamina) firmly to the main stem or branch of a plant?
A. Stalk (Petiole)
B. Midrib (Main vein)
C. Stomata
D. Side vein
20. How do herbivorous animals (like deer and cows) depend on sunlight for their survival, despite not performing photosynthesis themselves?
A. Herbivores absorb sunlight directly through their skin to produce glucose.
B. Herbivores eat green plants, which depend directly on sunlight to prepare food.
C. Sunlight warms herbivore blood, replacing their dietary need for food.
D. Sunlight converts atmospheric carbon dioxide into drinking water for herbivores.
21. Four potted plants were kept under different conditions:
Plant P: Sunlight, Water, Air
Plant Q: Dark Room, Water, Air
Plant R: Sunlight, No Water, Air
Plant S: Sunlight, Water, Sealed Glass Jar with CO₂ Removed
Which plant will successfully synthesize starch?
A. Plant P only
B. Plants P and Q
C. Plants P and R
D. Plant S only
22. Croton plants have leaves that appear dark red or purple rather than green. Can a croton plant perform photosynthesis, and why?
A. No, because red leaves lack chlorophyll completely.
B. Yes, because they contain chlorophyll hidden under dark red or purple pigments.
C. No, because red pigments reflect all solar radiation away.
D. Yes, because red pigments can absorb water from the air directly.
23. What happens to the oxygen gas produced during photosynthesis inside the green leaves?
A. It is completely stored in roots for winter survival.
B. It is converted into starch and stored in fruits.
C. It is released into the surrounding atmosphere through stomata.
D. It is absorbed by chlorophyll to give leaves their green color.
24. Which of the following plant parts represents extra food stored in the stem?
A. Spinach and Cabbage
B. Apple and Mango
C. Sugar cane and Potato
D. Carrot and Radish
25. Study the food chain: Grass → Grasshopper → Frog → Snake → Eagle. If the grass population is completely wiped out by disease, what will happen to the snake population?
A. Increase rapidly because snakes do not eat grass.
B. Remain completely unchanged because snakes eat frogs.
C. Eventually decrease because grasshoppers and frogs will starve due to lack of food.
D. Immediately transform into herbivorous primary consumers.
26. Which structural feature of a leaf is correctly paired with its specific function?
A. Stalk → Absorbs carbon dioxide from the surrounding air
B. Lamina (Leaf blade) → Provides broad surface area to absorb sunlight
C. Stomata → Transports prepared food directly down to roots
D. Midrib → Absorbs sunlight energy for leaf cells
27. Why do leaves usually appear green in color?
A. They reflect green color due to excess water in their cells.
B. They contain a green-colored pigment called chlorophyll.
C. Soil minerals absorbed by roots are green in color.
D. Sunlight contains only green light rays that shine on plants.
28. During a laboratory experiment, a student accidentally added iodine solution directly to an unboiled, fresh green leaf. No color change occurred. What is the reason for this result?
A. Fresh green leaves do not contain starch under any circumstances.
B. Iodine cannot penetrate the intact leaf cuticle and cell walls without boiling in water/alcohol.
C. Chlorophyll reacts with iodine to produce a clear colorless compound.
D. Unboiled leaves contain glucose, which destroys iodine.
29. Interdependence of plants and animals maintains gaseous balance in nature. Which of the following gas exchanges demonstrates this balance?
A. Plants release CO₂ used by animals; animals release O₂ used by plants.
B. Plants release O₂ used by animals; animals release CO₂ used by plants.
C. Plants and animals both absorb nitrogen gas directly during night.
D. Animals give carbon dioxide to plants, and plants give water vapor to carnivores only.
30. Which of the following statements about energy flow in a terrestrial food chain is TRUE?
A. Sun → Producers (Plants) → Consumers (Herbivores/Carnivores)
B. Carnivores → Herbivores → Producers → Sun
C. Producers → Sun → Herbivores → Carnivores
D. Sun → Carnivores → Herbivores → Producers
SECTION B: ANSWER KEY & DETAILED EXPLANATIONS
Detailed Step-by-Step Explanations:
Question 1 [Correct Option: B]
• Key Concept: Sunlight is essential for starch synthesis.
• Explanation: The black paper blocked sunlight from reaching the covered portion, preventing photosynthesis and starch formation. Thus, no blue-black color change occurred with iodine. The uncovered portion received sunlight, performed photosynthesis, produced starch, and turned blue-black.
Question 2 [Correct Option: B]
• Key Concept: Roots → Stem → Stalk → Main Vein → Side Veins → Leaf Cells
• Explanation: Water and dissolved soil minerals are absorbed by roots, travel up through the stem, enter the leaf via the stalk (petiole), pass through the main vein (midrib) and side veins, and are delivered to photosynthetic cells in the leaf blade.
Question 3 [Correct Option: C]
• Key Concept: Fleshy green stems perform photosynthesis.
• Explanation: Cactus leaves are reduced to sharp spines to minimize water loss via transpiration in dry deserts. The thick, fleshy green stem contains chlorophyll and takes over the function of manufacturing food via photosynthesis.
Question 4 [Correct Option: B]
• Key Concept: Dissolves and removes green chlorophyll pigment.
• Explanation: Boiling the leaf in alcohol breaks down and extracts green chlorophyll, bleaching/decolorizing the leaf. This ensures that the eventual blue-black color change during the iodine test is clearly visible without green masking.
Question 5 [Correct Option: B]
• Key Concept: Sun is the primary energy source passing to grass, deer, and lion.
• Explanation: Green plants (grass) are primary producers that convert solar energy into chemical energy (food) via photosynthesis. Herbivores (deer) eat grass, and carnivores (lion) eat herbivores, transferring solar energy through the food chain.
Question 6 [Correct Option: B]
• Key Concept: Gaseous exchange and transpiration.
• Explanation: Stomata are microscopic pores on the leaf surface that facilitate the entry of carbon dioxide (needed for photosynthesis) and the release of oxygen and excess water vapor.
Question 7 [Correct Option: C]
• Key Concept: Absorbs organic nutrients from dead/decaying matter.
• Explanation: Mushrooms lack chlorophyll and cannot perform photosynthesis. They are saprophytes that obtain nutrition by absorbing organic matter from decaying plant and animal matter in their surroundings.
Question 8 [Correct Option: B]
• Key Concept: Immediate product: Glucose | Stored form: Starch
• Explanation: During photosynthesis, leaves directly manufacture simple sugar (glucose) for energy. Excess glucose is converted into complex carbohydrate (starch) and stored across roots, stems, leaves, seeds, or fruits.
Question 9 [Correct Option: A]
• Key Concept: 1-Q (Carrot = Root), 2-S (Sugar cane = Stem), 3-P (Cabbage = Leaf), 4-R (Peas = Seed)
• Explanation: Carrot stores food in roots, Sugar cane stores food in stems, Cabbage stores food in leafy layers, and Peas store food inside seeds.
Question 10 [Correct Option: A]
• Key Concept: Oxygen depletes and carbon dioxide accumulates.
• Explanation: Green plants produce atmospheric oxygen and consume carbon dioxide during photosynthesis. Without plants, atmospheric oxygen would rapidly deplete due to animal respiration, while CO₂ levels would spike, causing ecological collapse.
Question 11 [Correct Option: B]
• Key Concept: Destarching the leaf completely.
• Explanation: Keeping a plant in total darkness for 24–72 hours prevents photosynthesis. The plant consumes all its pre-stored starch for survival energy, ensuring that any starch detected later is newly produced during the experiment.
Question 12 [Correct Option: C]
• Key Concept: Both statements 1 and 2 are true.
• Explanation: The midrib (main vein) runs central to the lamina. Side veins branch off to transport water/minerals to leaf cells and transport synthesized food away to other plant parts.
Question 13 [Correct Option: B]
• Key Concept: Van Mahotsava
• Explanation: Van Mahotsava is an annual national tree-planting festival in India (celebrated in the first week of July) aimed at increasing forest cover and raising environmental awareness.
Question 14 [Correct Option: B]
• Key Concept: Leaves synthesize food (glucose) for the plant.
• Explanation: Leaves contain chlorophyll, stomata, and vein networks, making them the primary site where raw materials (CO₂, water, light energy) are combined to cook/synthesize food (glucose).
Question 15 [Correct Option: A]
• Key Concept: Items 1 (Boiled rice) and 2 (Potato slice)
• Explanation: Boiled rice and potatoes are rich in starch, which reacts with iodine solution to form a characteristic blue-black complex. Cooking oil (fats) and sugar cubes (simple sugars) do not give a blue-black iodine test.
Question 16 [Correct Option: B]
• Key Concept: Traps solar light energy.
• Explanation: Chlorophyll is the green pigment present inside leaf cells that absorbs and traps solar radiation, providing the driving energy for photosynthesis.
Question 17 [Correct Option: B]
• Key Concept: Carbon dioxide + Water + Sunlight (Chlorophyll) → Glucose + Oxygen
• Explanation: The standard chemical representation of photosynthesis shows carbon dioxide reacting with water in the presence of sunlight and chlorophyll to form glucose and oxygen gas.
Question 18 [Correct Option: B]
• Key Concept: Lack of sunlight prevented photosynthesis.
• Explanation: Without sunlight inside the light-proof box, chlorophyll could not trap energy to perform photosynthesis. Despite receiving water, the plant starved once its internal starch reserves were exhausted.
Question 19 [Correct Option: A]
• Key Concept: Stalk (Petiole)
• Explanation: The leaf stalk (petiole) attaches the flattened leaf blade (lamina) to the main plant stem or branch, providing support and vascular connection.
Question 20 [Correct Option: B]
• Key Concept: Herbivores eat green plants that rely on solar energy.
• Explanation: All food energy originates from the sun. Herbivores do not perform photosynthesis, but they survive entirely by consuming green plants that convert solar energy into chemical food energy.
Question 21 [Correct Option: A]
• Key Concept: Plant P only
• Explanation: Photosynthesis requires all four factors: sunlight, water, carbon dioxide, and chlorophyll. Plant Q lacks sunlight, Plant R lacks water, and Plant S lacks CO₂. Only Plant P has all required inputs to produce starch.
Question 22 [Correct Option: B]
• Key Concept: Yes, chlorophyll is present beneath red/purple pigments.
• Explanation: Croton leaves contain abundant chlorophyll, but dark red, purple, or brown pigments mask the green color. Chlorophyll still absorbs sunlight and performs photosynthesis normally.
Question 23 [Correct Option: C]
• Key Concept: Released into atmosphere via stomata.
• Explanation: Oxygen is generated as a byproduct of photosynthesis. It diffuses out of the leaf through stomata, enriching atmospheric air for animal and plant respiration.
Question 24 [Correct Option: C]
• Key Concept: Sugar cane and Potato
• Explanation: Sugar cane stores extra food in its thick stem, and potato is a modified underground stem (tuber) that stores starch. Carrot/radish are roots, while spinach/cabbage are leaves.
Question 25 [Correct Option: C]
• Key Concept: Eventually decreases due to starvation in food chain.
• Explanation: Grasshoppers depend directly on grass for food. If grass disappears, grasshoppers die off, causing frogs (which eat grasshoppers) and subsequently snakes (which eat frogs) to starve.
Question 26 [Correct Option: B]
• Key Concept: Lamina (Leaf blade) provides broad surface area for sunlight.
• Explanation: The expanded flat lamina maximizes solar absorption. Stalk attaches leaf to stem, stomata handle gas exchange, and midrib transports water/food.
Question 27 [Correct Option: B]
• Key Concept: Contains green pigment chlorophyll.
• Explanation: Chlorophyll is a specialized green pigment in chloroplasts that absorbs sunlight for photosynthesis, giving leaves their characteristic green color.
Question 28 [Correct Option: B]
• Key Concept: Iodine cannot cross waxy cuticle and cell walls without boiling.
• Explanation: Boiling in water kills the leaf cells and disrupts cell walls/cuticle, allowing iodine solution to penetrate into leaf tissue and react with stored starch.
Question 29 [Correct Option: B]
• Key Concept: Plants release O₂ (used by animals); animals release CO₂ (used by plants).
• Explanation: Photosynthesis consumes CO₂ and releases O₂. Animal respiration consumes O₂ and releases CO₂. This complementary cycle maintains balanced atmospheric gas levels.
Question 30 [Correct Option: A]
• Key Concept: Sun → Producers (Plants) → Consumers (Herbivores/Carnivores)
• Explanation: Solar energy enters biological systems through green plants (producers) via photosynthesis, and then flows to herbivores (primary consumers) and carnivores (secondary consumers).