Question 1

Complete the following table

|  S.No. | Feature | Photosynthesis | Respiration  |
| --- | --- | --- | --- |
|  1. | Raw materials |  |   |
|  2. | Products |  |   |
|  3. | Word equation |  |   |
|  4. | Importance |  |   |

Accepted Answer

1. Raw materials:
- Photosynthesis: Carbon dioxide, water, sunlight
- Respiration: Glucose, oxygen

2. Products:
- Photosynthesis: Glucose, oxygen
- Respiration: Carbon dioxide, water, energy

3. Word equation:
- Photosynthesis: Carbon dioxide + Water + Sunlight → Glucose + Oxygen
- Respiration: Glucose + Oxygen → Carbon dioxide + Water + Energy

4. Importance:
- Photosynthesis: Produces food and oxygen necessary for life
- Respiration: Releases energy required for various life processes — Photosynthesis uses carbon dioxide and water in presence of sunlight to produce glucose and oxygen. Respiration breaks down glucose using oxygen to release energy, carbon dioxide and water. The table summarizes these features.

Question 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?

Accepted Answer

If all photosynthetic organisms disappeared, oxygen levels would decrease as photosynthesis produces oxygen. Food chains would collapse because plants are primary producers. Animals and other organisms dependent on plants for food and oxygen would eventually die, leading to a breakdown of ecosystems. — Photosynthetic organisms produce oxygen and food which are essential for survival of other organisms. Without them, life on Earth would not sustain.

Question 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?

Accepted Answer

The starch in potatoes comes from the glucose produced during photosynthesis in the leaves. The food is synthesised in the leaves (the food factories) of the plant. The glucose is transported through the phloem to the potato (a storage organ) where it is converted into starch and stored. — Leaves perform photosynthesis producing glucose. This glucose is transported via phloem to storage organs like potatoes where it is stored as starch.

Question 4

Does the broad and flat structure of leaves make plants more efficient for photosynthesis? Justify your answer.

Accepted Answer

Yes, the broad and flat structure of leaves increases the surface area exposed to sunlight, allowing more light to be absorbed for photosynthesis. It also facilitates efficient gas exchange through stomata, making photosynthesis more efficient. — A larger surface area allows more sunlight absorption and better gas exchange, both essential for photosynthesis.

Question 5

X is broken down using Y to release carbon dioxide, Z, and energy.

$$
\mathrm{X} + \mathrm{Y} \longrightarrow 	ext{Carbon dioxide} + \mathrm{Z} + 	ext{Energy}
$$

X, Y, and Z are three different components of the process.

What do X, Y, and Z stand for?

Accepted Answer

X = Glucose
Y = Oxygen
Z = Water

This equation represents respiration where glucose is broken down using oxygen to release carbon dioxide, water, and energy. — In respiration, glucose (X) reacts with oxygen (Y) to produce carbon dioxide, water (Z), and energy.

Question 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?
(ii) What are the visible differences in plants in both the conditions?
(iii) According to you, leaves of which plants confirm the iodine test for the presence of starch?

Accepted Answer

(i) Krishna might be testing the effect of sunlight on photosynthesis and starch formation in plants.

(ii) The plant in sunlight will appear healthy and green, while the plant in the dark will be pale, weak, and may have yellowish leaves due to lack of chlorophyll.

(iii) Leaves of the plant kept in sunlight will confirm the iodine test for starch presence because photosynthesis occurs in sunlight producing starch. Leaves of the plant kept in dark will not show starch. — Sunlight is essential for photosynthesis which produces starch. Plants kept in dark cannot photosynthesise effectively, so starch is absent.

Question 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?
(ii) In which plant(s) in the above set-up(s) will starch not be formed?
(iii) In which plant(s) in the above set-up(s) will oxygen be generated?
(iv) In which plant(s) in the above set-up(s) will oxygen not be generated?

Accepted Answer

(i) Starch will be formed in plant (a) Sunlight with carbon dioxide.

(ii) Starch will not be formed in plants (b) Sunlight without carbon dioxide, (c) Dark with carbon dioxide, and (d) Dark without carbon dioxide.

(iii) Oxygen will be generated in plant (a) Sunlight with carbon dioxide.

(iv) Oxygen will not be generated in plants (b), (c), and (d) because photosynthesis requires both sunlight and carbon dioxide. — Photosynthesis requires both sunlight and carbon dioxide to produce starch and oxygen. Absence of either prevents starch formation and oxygen release.

Question 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?

Accepted Answer

Ananya wants to find out the role of plants and animals in carbon dioxide exchange.

She will observe the colour changes of the carbon dioxide indicator:
- In test tube A (snail only), carbon dioxide will increase due to respiration, indicator changes colour accordingly.
- In test tube B (plant only), carbon dioxide will decrease due to photosynthesis, indicator changes colour accordingly.
- In test tube C (snail and plant), carbon dioxide levels may remain balanced due to respiration and photosynthesis, indicator shows little or no change.
- In test tube D (water only), no change in indicator colour.

If the indicator changes as expected, her hypothesis about carbon dioxide exchange is correct. — Snails produce CO2 by respiration; plants consume CO2 by photosynthesis. The indicator shows CO2 presence by colour change, confirming these processes.

Question 9

Design an experiment to observe if water transportation in plants is quicker in warm or cold conditions.

Accepted Answer

Experiment Design:
- Take two similar plants or cut stems.
- Place one in a warm environment and the other in a cold environment.
- Add coloured water (with food colouring) to the base of both plants.
- Observe the time taken for the coloured water to reach the leaves.
- The plant in warm conditions will show quicker water transportation due to increased transpiration rate.

Conclusion: Water transportation is quicker in warm conditions. — Warm temperature increases transpiration, creating a stronger pull for water movement through xylem, speeding up water transport.

Question 10

Photosynthesis and respiration are essential to maintain balance in nature. Discuss.

Accepted Answer

Photosynthesis produces oxygen and glucose, which are essential for respiration in living organisms. Respiration uses oxygen to break down glucose, releasing energy and carbon dioxide. The carbon dioxide is then used again in photosynthesis. This cyclical process maintains the balance of oxygen and carbon dioxide in the atmosphere, supporting life on Earth. — The interdependence of photosynthesis and respiration keeps atmospheric gases balanced and provides energy for living organisms.

Question 11

Which of the following factors are essential for the growth of plants as demonstrated by the experiment with pots A, B, and C?

Accepted Answer

Sunlight and water — The experiment with pots A, B, and C showed that the plant in pot A, which received both sunlight and water, grew best. Pot B, with sunlight but no water, the plant died, and pot C, with water but no sunlight, showed poor growth. This indicates that both sunlight and water are essential for plant growth.

Question 12

What changes do plants undergo as they grow?

Accepted Answer

Plants grow by increasing in height, developing new leaves and branches, and thickening their stems. For example, a sapling of a chilli plant grows taller and produces more leaves over time. — Plants show visible growth by increasing their height and weight. They develop new leaves and branches, and their stems become thicker. These changes are indicators of growth in plants.

Question 13

Why are leaves called the 'food factories' of plants?

Accepted Answer

Leaves are called the 'food factories' of plants because they prepare food in the form of starch using sunlight, water, carbon dioxide, and chlorophyll. For example, starch is produced in the green parts of leaves where chlorophyll is present. — Leaves contain chlorophyll which captures sunlight. Using sunlight, water, and carbon dioxide, leaves synthesize glucose which is stored as starch. This process is called photosynthesis, making leaves the primary site for food production in plants.

Question 14

In Activity 10.2, why is the leaf first boiled in water and then placed in alcohol before testing for starch?

Accepted Answer

The leaf is boiled in water to soften it and then placed in alcohol to remove chlorophyll and decolourise it. This allows the iodine solution to easily show a colour change indicating the presence of starch. For example, a decolourised leaf turns blue-black when iodine is applied if starch is present. — Boiling softens the leaf tissues, and alcohol removes the green pigment chlorophyll, which would otherwise mask the colour change. Decolourisation helps in clearly observing the blue-black colour formed by the iodine-starch reaction.

Question 15

What conclusion can be drawn from Bhaskar's experiment where leaves with green and non-green patches were tested for starch after being kept in sunlight and dark?

Accepted Answer

The experiment shows that starch is produced only in the green patches of leaves that contain chlorophyll and are exposed to sunlight. Non-green patches do not produce starch. For example, leaves kept in sunlight showed blue-black colour in green patches after iodine test, while leaves kept in dark showed no starch production. — Chlorophyll is necessary for photosynthesis and starch production. Green patches contain chlorophyll and can prepare starch in sunlight. Non-green patches lack sufficient chlorophyll and do not produce starch, and leaves kept in dark do not photosynthesize.

Life Processes in Plants

Life Processes in Plants — Study Notes

Life Processes in Plants

10.1 How Do Plants Grow?

10.2 How Do Plants Get Food for their Growth?

Practice Questions — Life Processes in Plants

All 12 Chapters in Curiosity