Life Processes in Plants — Class 7 Science
Curiosity · Chapter 10
CBSE Class 7 community
View all
7- Mathematics
- Science
- + 3 more
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
2- Mathematics
- Social Science
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
Chapter summary
Key ideas & terms
- Photosynthesis
- The process by which plants make food in the form of glucose using sunlight, chlorophyll, carbon dioxide, and water, releasing oxygen.
- Chlorophyll
- The green pigment in leaves that captures sunlight and is essential for the preparation of starch.
- Stomata
- Tiny pores on the surface of leaves that help in the exchange of gases during photosynthesis and respiration.
- Xylem
- The tube-like structures that transport water and dissolved minerals from the roots to other parts of the plant.
- Phloem
- The tube-like structures that transport food made in the leaves to all parts of the plant.
- Respiration in plants
- The process by which plants break down glucose using oxygen to release carbon dioxide, water, and energy.
Extra questions & answers
What two factors do experiments show are essential for plant growth?
Experiments show that plants need both sunlight and water; a plant without water dies and one kept in the dark grows poorly even with water.
Why are leaves called the food factories of plants?
Leaves are broad, flat, and green with chlorophyll, and it is in the leaves that plants prepare and store food as starch through photosynthesis.
How is the presence of starch in a leaf tested?
Starch is detected with the iodine test: where starch is present the decolourised leaf turns blue-black.
What does Activity 10.3 show about where starch is formed?
It shows that starch forms only in the green, sunlit patches of a leaf, confirming that both chlorophyll and sunlight are needed.
How is it shown that carbon dioxide is needed for photosynthesis?
When part of a leaf is enclosed with caustic soda (which absorbs carbon dioxide), that part forms no starch, showing carbon dioxide is essential.
Write the word equation for photosynthesis.
Carbon dioxide + Water gives Glucose + Oxygen, in the presence of sunlight and chlorophyll.
What are stomata and what do they do?
Stomata are tiny pores on the surface of leaves that allow the exchange of gases during photosynthesis and respiration.
What do xylem and phloem transport?
Xylem transports water and minerals from the roots upward, while phloem carries the food made in the leaves to all parts of the plant.
How is it shown that plants respire?
Germinating seeds in a flask connected to lime water turn the lime water milky, showing the seeds release carbon dioxide as they respire.
Write the word equation for respiration in plants.
Glucose + Oxygen gives Carbon dioxide + Water + Energy.
Let Us Enhance Our Learning
1. Complete the following table
S.No. Feature Photosynthesis Respiration
1. Raw materials
2.
3. Products
4. Importance
Word equation
The completed comparison is:
| Feature | Photosynthesis | Respiration |
|---|---|---|
| 1. Raw materials | Carbon dioxide
| 2. Need for sunlight / chlorophyll | Required - occurs only in presence of sunlight and chlorophyll | Not required - occurs all the time in all living cells day and night |
| 3. Products | Glucose
| 4. Importance | Makes food for the plant and releases oxygen for all living beings | Breaks down food to release energy needed for growth and other life activities |
| Word equation |
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?
If all photosynthetic organisms disappeared, the source of food and oxygen would stop. Green plants make glucose and release
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?
Food is synthesised mainly in the green leaves, which are the food factories of the plant, by photosynthesis:
4. Does the broad and flat structure of leaves make plants more efficient for photosynthesis? Justify your answer.
Yes. A broad and flat leaf has a large surface area. This helps to capture more sunlight and also exposes more stomata to take in
5. X is broken down using Y to release carbon dioxide, Z, and energy.
X, Y, and Z are three different components of the process.
What do X, Y, and Z stand for?
The equation represents respiration:
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?
She is testing whether sunlight is necessary for plant growth and for making starch by photosynthesis. By keeping everything else the same like pot size, soil, water and plant type and changing only light, she can see the effect of sunlight.
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 — (ii) What are the visible differences in plants in both the conditions?
The plant kept in sunlight will grow well, stay green, increase in height and have more and healthier leaves. The plant kept in complete darkness will show poor growth, its leaves will turn pale or yellow and may droop, its stem may become weak and thin, and it may not produce new leaves.
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 — (iii) According to you, leaves of which plants confirm the iodine test for the presence of starch?
Leaves of the plant kept in sunlight will give a positive iodine test. When decolourised and treated with iodine solution they turn blue-black, showing starch is present because photosynthesis could occur. Leaves of the plant kept in the dark will not turn blue-black, showing no starch was formed.
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. Fig. 10.11: A potted plant with sufficient water is placed under the prescribed conditions (a) Sunlight with carbon dioxide (b) Sunlight without carbon dioxide (c) Dark with carbon dioxide (d) Dark without carbon dioxide Answer the following questions — (i) In which plant(s) in the above set-up(s) will starch be formed?
Starch will be formed only in plant (a) which gets both sunlight and carbon dioxide together with water and chlorophyll. Only this set has all the requirements for photosynthesis.
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. Fig. 10.11: A potted plant with sufficient water is placed under the prescribed conditions (a) Sunlight with carbon dioxide (b) Sunlight without carbon dioxide (c) Dark with carbon dioxide (d) Dark without carbon dioxide Answer the following questions — (ii) In which plant(s) in the above set-up(s) will starch not be formed?
Starch will not be formed in plants (b), (c) and (d). Plant (b) lacks
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. Fig. 10.11: A potted plant with sufficient water is placed under the prescribed conditions (a) Sunlight with carbon dioxide (b) Sunlight without carbon dioxide (c) Dark with carbon dioxide (d) Dark without carbon dioxide Answer the following questions — (iii) In which plant(s) in the above set-up(s) will oxygen be generated?
Oxygen is released only when photosynthesis occurs, so only plant (a) with sunlight and carbon dioxide will generate oxygen.
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. Fig. 10.11: A potted plant with sufficient water is placed under the prescribed conditions (a) Sunlight with carbon dioxide (b) Sunlight without carbon dioxide (c) Dark with carbon dioxide (d) Dark without carbon dioxide Answer the following questions — (iv) In which plant(s) in the above set-up(s) will oxygen not be generated?
Oxygen will not be generated in plants (b), (c) and (d) because photosynthesis does not take place without both
8. Ananya took four test tubes and filled three-fourth 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?
Ananya wants to find out how photosynthesis and respiration affect the amount of
9. Design an experiment to observe if water transportation in plants is quicker in warm or cold conditions.
Take two similar white-flowered twigs like balsam and two tumblers with water coloured with red ink. Keep one tumbler in a warm place like in sunlight and the other in a cold place like near ice or in a refrigerator. Place one twig in each tumbler after making a slant cut under water. Observe after a few hours. The twig in the warm condition will show red colour in stem, leaves and flowers faster than the cold one because transpiration and water movement through xylem is faster in warm air. Measuring the time taken for the red colour to appear shows that water transport is quicker in warm conditions.
10. Photosynthesis and respiration are essential to maintain balance in nature. Discuss.
Photosynthesis uses