Class 7 Science Curiosity Chapter 10 Life Processes In Plants NCERT Solutions
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1. Complete the following table
Answer:
2. Imagine a situation where all the organisms that carry out photosynthesis on the earth have disappeared. What would be the impact of this on living organisms?
Answer:
If all photosynthetic organisms disappeared, no oxygen and food would be produced. All animals, including humans, would eventually die because there would be no oxygen to breathe and no plants to begin the food chain.
3. A potato slice shows the presence of starch with iodine solution. Where does the starch in potatoes come from? Where is the food synthesised in the plant, and how does it reach the potato?
Answer:
The starch in potatoes comes from the glucose produced during photosynthesis. Food is synthesised in the leaves of the plant. The glucose formed in the leaves is transported to different parts of the plant, including the potato, where it is stored in the form of starch.
4. Does the broad and flat structure of leaves make plants more efficient for photosynthesis? Justify your answer.
Answer:
Yes, the broad and flat structure of leaves makes plants more efficient in photosynthesis. This is because a larger surface area helps the leaves absorb more sunlight and allows better exchange of gases needed for photosynthesis.
5. X is broken down using Y to release carbon dioxide, Z, and energy.
X + Y → Carbon dioxide + Z + Energy
X, Y, and Z are three different components of the process. What do X, Y, and Z stand for?
Answer:
X = Glucose
Y = Oxygen
Z = Water
So,
Glucose + Oxygen → Carbon dioxide + Water + Energy.
6. Krishna set-up an experiment with two potted plants of same size and placed one of them in sunlight and the other in a dark room, as shown in Fig. 10.10.
Answer the following questions —
(i) What idea might she be testing through this experiment?
Answer:
She might be testing whether sunlight is necessary for photosynthesis.
(ii) What are the visible differences in plants in both the conditions?
Answer:
The plant kept in sunlight appears green, healthy, and has broader leaves. The plant kept in the dark room appears pale or yellowish and looks weak.
(iii) According to you, leaves of which plants confirm the iodine test for the presence of starch?
Answer:
The leaves of the plant kept in sunlight will confirm the iodine test for starch, because photosynthesis occurs only in the presence of sunlight.
7. Vani believes that ‘carbon dioxide is essential for photosynthesis’. She puts an experimental set-up, as shown in Fig. 10.11, to collect evidence to support or reject her idea.
Answer the following questions —
(i) In which plant(s) in the above set-up(s) will starch be formed?
Answer:
Starch will be formed only in plant (a) — sunlight with carbon dioxide.
(ii) In which plant(s) in the above set-up(s) will starch not be formed?
Answer:
Starch will not be formed in plants (b), (c), and (d) because either carbon dioxide or sunlight is missing.
(iii) In which plant(s) in the above set-up(s) will oxygen be generated?
Answer:
Oxygen will be generated only in plant (a) because photosynthesis takes place only when both sunlight and carbon dioxide are available.
(iv) In which plant(s) in the above set-up(s) will oxygen not be generated?
Answer:
Oxygen will not be generated in plants (b), (c), and (d) because photosynthesis does not occur in these conditions.
8. Ananya took four test tubes and filled three-fourths of each test tube with water. She labelled them A, B, C, and D (Fig. 10.12). In test tube A, she kept a snail; in test tube B, she kept a water plant; in test tube C, she kept both a snail and a plant. In test tube D, she kept only water. Ananya added a carbon dioxide indicator to all the test tubes. She recorded the initial colour of water and observed if there are any colour changes in the test tubes after 2–3 hours. What do you think she wants to find out? How will she know if she is correct?
Answer:
Ananya wants to find out how plants and animals affect the amount of carbon dioxide in water.
• In test tube A (snail), the snail respires and releases carbon dioxide, so the indicator will show an increase in CO₂.
• In test tube B (water plant), the plant uses carbon dioxide for photosynthesis, so the indicator will show a decrease in CO₂.
• In test tube C (snail + plant), the plant will use the CO₂ released by the snail, so the indicator may show little or no change.
• In test tube D (only water), there will be no change in CO₂ level.
She will know she is correct if the colour of the indicator changes according to the amount of carbon dioxide present in each test tube.
9. Design an experiment to observe if water transportation in plants is quicker in warm or cold conditions.
Answer:
Take two identical leafy stems and place them in two beakers containing coloured water. Keep one beaker in a warm place and the other in a cold place. After some time, observe the rise of coloured water in both stems. The stem kept in the warm place will show faster upward movement of coloured water. This shows that water transportation in plants is quicker in warm conditions than in cold conditions.
10. Photosynthesis and respiration are essential to maintain balance in nature. Discuss.
Answer:
In photosynthesis, plants use carbon dioxide and water to make food and release oxygen. In respiration, plants and animals use oxygen to break down food and release carbon dioxide and energy. These two processes balance the amounts of oxygen and carbon dioxide in the atmosphere. Therefore, photosynthesis and respiration together help in maintaining balance in nature.
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