Class 7 Science Quiz – Photosynthesis

Q1. The statement “Trees do not produce fruits and flowers merely because they are planted” emphasizes which idea?

A. Plant growth depends only on climate B. Successful crop production requires informed and systematic practices C. Agriculture depends on divine forces D. Soil fertility is unimportant

Answer: B
Planting alone is not sufficient. The statement highlights the importance of knowledge-based, systematic agricultural practices developed through observation and experience over time.

Q2. Which of the following best describes the nature of agricultural knowledge recorded in Vrikshayurveda?

A. Theoretical ideas based on philosophy B. Ideas derived from foreign systems C. Practices developed through long-term observation and experience D. Techniques limited to irrigation

Answer: C
The text reflects empirical learning — knowledge based on repeated observation and practice over time, showing early scientific thought in Indian agriculture.

Q3. Why is a leaf decolourised before performing the iodine test for starch?

A. To remove dust and impurities B. To prevent the leaf from burning C. To make the colour change due to iodine clearly visible D. To increase starch content

Answer: C
Decolourising removes chlorophyll, revealing the colour change when iodine reacts with starch, making the test result visible and accurate.

Q4. Some plant leaves appear red, violet, or brown. What does the iodine test in such leaves indicate?

A. Photosynthesis does not occur B. Coloured pigments replace chlorophyll C. Starch may still be present, proving photosynthesis occurs D. Only green leaves store food

Answer: C
Even coloured leaves contain chlorophyll masked by other pigments. The iodine test turning blue-black shows starch formation and indicates photosynthesis.

Q5. What conclusion is drawn when starch forms only in the green patches of a leaf?

A. Sunlight alone is enough for starch formation B. Chlorophyll is essential for starch formation in sunlight C. All leaf parts form starch equally D. Other pigments produce food

Answer: B
Only chlorophyll-containing areas produce starch, proving chlorophyll’s key role in using sunlight during photosynthesis.

Q6. In the experiment where part of a leaf is inside a bottle containing caustic soda, why does that part fail to turn blue-black after the iodine test?

A. Chlorophyll is destroyed B. Sunlight cannot enter the bottle C. Carbon dioxide is absorbed by caustic soda D. Water supply is cut off

Answer: C
Caustic soda removes carbon dioxide, an essential raw material for photosynthesis. Without CO₂, starch cannot form in that enclosed part.

Q7. Based on experiments, which part of the plant is the main site of starch synthesis?

A. Roots B. Colourless leaves C. Green leaves D. All parts equally

Answer: C
Leaf chlorophyll captures sunlight, helping form starch — confirming that leaves are the primary photosynthetic and starch-synthesizing sites.

Q8. What happens to the glucose produced during photosynthesis?

A. Stored directly as glucose B. Released into the atmosphere C. Used for energy and stored as starch D. Converted only into oxygen

Answer: C
Glucose provides immediate energy and is converted into starch for storage when in excess — a key process in plant metabolism.

Q9. Which structure mainly allows exchange of carbon dioxide and oxygen during photosynthesis?

A. Lenticels B. Xylem C. Stomata D. Phloem

Answer: C
Stomata on leaves control gas exchange — taking in carbon dioxide and releasing oxygen during photosynthesis.

Q10. What confirms upward water movement in the red-ink experiment?

A. Only roots turn red B. Red colour appears in stem, leaves, and flowers C. Red colour remains in the tumbler D. Leaves lose colour

Answer: B
The spread of red colour to aerial parts proves that water is transported upward through the plant body.

Q11. Which tissue transports water and minerals from roots to leaves?

A. Phloem B. Cortex C. Xylem D. Cambium

Answer: C
Xylem vessels form channels that carry water and minerals upward, demonstrated clearly in the red-ink movement.

Q12. Why is red ink used in the water-transport activity?

A. To increase photosynthesis B. To make the path of water movement visible C. To provide nutrients D. To stop mineral transport

Answer: B
Red ink helps trace the movement of water through the plant, visually showing the xylem’s function in transport.

Q13. What does red colour in the cut stem section indicate?

A. Food storage in stem B. Damage to tissues C. Xylem vessels carrying water D. Stomata in the stem

Answer: C
The red colour marks xylem vessels that carry coloured water upward, confirming their transport role.

Q14. Which tissue transports food prepared in the leaves to other parts of the plant?

A. Xylem B. Phloem C. Stomata D. Root hairs

Answer: B
Phloem carries the sugars produced in leaves to non-photosynthetic parts, supporting growth and storage.

Q15. Where can food transported by the phloem be stored?

A. Only in leaves B. Only in stems C. In seeds and roots D. Only in flowers

Answer: C
Phloem transports food to storage organs like seeds and roots, ensuring stored energy for growth and new plants.

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