RBSE Solutions Class 7 Science Chapter 10 Life Processes in Plants

Class 7 Science Curiosity Chapter 10 Question Answer (Exercise)

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Question 1. Complete the following table.
Answer:

🎯 Exam Tip: Remember the inputs and outputs for each process. Photosynthesis consumes \( \text{CO}_2 \) and releases \( \text{O}_2 \), while respiration consumes \( \text{O}_2 \) and releases \( \text{CO}_2 \).

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?
Answer: If all photosynthetic organisms, like plants and algae, disappeared from Earth, it would have very serious impacts. First, the production of oxygen would stop, which means there would soon be no oxygen for breathing in the atmosphere. Life needs oxygen to survive.
Second, the food chain would break completely. Plants are the main producers of food, forming the base of all food chains. Without them, animals would not have food and would die. This would lead to a massive collapse of ecosystems.
Finally, the amount of carbon dioxide in the atmosphere would increase a lot. This is because plants use \( \text{CO}_2 \) during photosynthesis. More \( \text{CO}_2 \) would lead to increased global warming, making the Earth too hot to live on. Photosynthesis is vital for both food and atmospheric balance.
In simple words: If all plants disappeared, there would be no oxygen to breathe and no food to eat, so all living things would die. The air would also have too much carbon dioxide, making the Earth much hotter.

🎯 Exam Tip: When discussing impacts, always consider both the immediate effects (like lack of oxygen/food) and the long-term environmental consequences (like carbon dioxide buildup and global warming).

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 synthesized in the plant, and how does it reach the potato?
Answer: The starch in potatoes comes from the food that the potato plant makes through a process called photosynthesis. The primary food synthesis, or making, happens in the leaves of the plant, mainly in specialized cells containing chloroplasts.
Once glucose (a simple sugar) is made in the leaves, it is transported through the plant's vascular system, specifically the phloem, to other parts of the plant where it is needed for energy or storage. For the potato plant, this glucose is sent to underground stems called tubers (which are the potatoes we eat). Inside these tubers, the glucose is converted into starch and stored there as an energy reserve for the plant.
In simple words: Potatoes get their starch from the sugar made in the plant's leaves through sunlight. This sugar travels down to the potato part underground, where it changes into starch for storage.

🎯 Exam Tip: Remember that leaves are the food factories, glucose is the initial product, and starch is the stored form, often found in storage organs like roots, seeds, or tubers.

Question 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: In the given process, which describes respiration:
\( \text{X} \) stands for **glucose** (the food source).
\( \text{Y} \) stands for **oxygen** (used to break down glucose).
\( \text{Z} \) stands for **water** (a product of respiration).
So, glucose is broken down using oxygen to release carbon dioxide, water, and energy.
In simple words: \( \text{X} \) is glucose, which is like food. \( \text{Y} \) is oxygen, which helps burn the food. \( \text{Z} \) is water, which is made during the burning. Energy is released when glucose is broken down by oxygen.

🎯 Exam Tip: Always remember the basic equation for respiration: Glucose + Oxygen → Carbon dioxide + Water + Energy. This helps identify the components.

Question 6. Krishna step-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?
Answer:
(i) Krishna is testing if **sunlight is necessary for photosynthesis** to occur in plants. Photosynthesis is the process plants use to make their food.
(ii) The plant kept in sunlight will grow well and its leaves will be green and healthy. The plant kept in the dark room, however, will likely have yellowing leaves (a condition called etiolation) and show very little growth. This is because it cannot make food without light.
(iii) The leaves of the plant kept in **sunlight** will test positive for the presence of starch when an iodine solution is applied. The leaves will turn blue-black, indicating starch. The plant in the dark will not have starch, as it couldn't photosynthesize.
In simple words: Krishna wants to see if plants need sunlight to make food. The plant in sunlight will be green and healthy, while the one in the dark will turn yellow and not grow much. Only the leaves from the plant kept in sunlight will show starch when tested with iodine.

🎯 Exam Tip: This classic experiment clearly demonstrates the vital role of sunlight in photosynthesis and starch production. A positive iodine test (blue-black color) always confirms starch presence.

Question. 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?
Answer:
(i) Starch will be formed in setup **(a)**. This is because sunlight and carbon dioxide are both present, which are essential for photosynthesis.
(ii) Starch will not be formed in setups **(b), (c), and (d)**. In (b), carbon dioxide is absent; in (c) and (d), there is no sunlight. Without either sunlight or carbon dioxide, photosynthesis cannot happen.
(iii) Oxygen will be generated in setup **(a)**. Oxygen is a byproduct of photosynthesis, which occurs when both sunlight and carbon dioxide are available.
(iv) Oxygen will not be generated in setups **(b), (c), and (d)**. Because photosynthesis does not occur in these setups due to the lack of either carbon dioxide or sunlight.
In simple words: Starch and oxygen are made only when a plant gets both sunlight and carbon dioxide, which happens in setup (a). If either is missing, like in (b), (c), and (d), then no starch or oxygen is produced.

🎯 Exam Tip: Remember that both light and carbon dioxide are critical raw materials for photosynthesis. Removing either stops the process and prevents the formation of starch and the release of oxygen.

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?
Answer: Ananya wants to find out how living organisms, specifically snails (animals) and water plants, affect the **amount of carbon dioxide** in their environment (water). She uses a carbon dioxide indicator because its color changes depending on how much \( \text{CO}_2 \) is present.
She will know if she is correct by observing the color changes in the indicator solution in each test tube. For instance, if the indicator turns from violet to yellow, it means carbon dioxide has increased. In test tube 'A' (with only a snail) and 'C' (with both snail and plant), the color will change because the snail's respiration releases \( \text{CO}_2 \). In test tube 'B' (with only a plant), the \( \text{CO}_2 \) level might decrease or stay stable if the plant photosynthesizes effectively, consuming the \( \text{CO}_2 \). This experiment helps show the exchange of gases by living things.
In simple words: Ananya wants to learn how much carbon dioxide is made by animals and used by plants. She will know by watching the water change color: yellow means more carbon dioxide, and it happens when animals breathe out.

🎯 Exam Tip: This experiment is a classic way to demonstrate respiration (animals release \( \text{CO}_2 \)) and photosynthesis (plants absorb \( \text{CO}_2 \)). The key is understanding how the \( \text{CO}_2 \) indicator works and what its color changes signify.

Question 9. Design an experiment to observe if water transportation in plants is quicker in warm or cold conditions?
Answer: To observe if water transportation in plants is quicker in warm or cold conditions, we can design the following experiment:
**Experiment:**
1. Take two similar potted plants, ensuring they are of the same size and type.
2. Prepare two beakers filled with colored water. You can use a food coloring to make the water clearly visible.
3. Place one plant in the colored water in a warm environment (e.g., near a window in sunlight, or in a room with a heater).
4. Place the second plant in the colored water in a cold environment (e.g., in a cooler area, or a room with air conditioning).
5. Observe both plants for a few hours. Check to see how quickly the colored water rises up the stem and into the leaves of each plant.
**Observation:** You will notice that the colored water rises faster in the plant kept in the warm condition. This is because warm conditions increase the rate of transpiration (evaporation of water from leaves), which in turn pulls water up the plant more quickly.
In simple words: Take two plants and put them in colored water. Keep one warm and one cold. The plant in the warm place will suck up the colored water faster because warmth makes water leave its leaves quicker, pulling more water up.

🎯 Exam Tip: When designing an experiment, always ensure you have a control group or controlled variables (same plant type, same water amount, etc.) and only one changing variable (temperature) to ensure accurate results.

Question 10. Photosynthesis and respiration are essential to maintain balance in nature. Discuss.
Answer: Photosynthesis and respiration are two opposing but complementary processes that are absolutely essential for maintaining a natural balance on Earth, especially regarding atmospheric gases and energy flow. Photosynthesis, carried out by plants, uses carbon dioxide from the atmosphere and releases oxygen. This helps to reduce \( \text{CO}_2 \) levels and replenish oxygen.
On the other hand, respiration, which occurs in both plants and animals, uses oxygen from the atmosphere and releases carbon dioxide. These two processes work together in a cycle: the oxygen produced by photosynthesis is used in respiration, and the carbon dioxide released by respiration is used in photosynthesis. This continuous exchange helps to keep the levels of oxygen and carbon dioxide in the atmosphere stable. Without this delicate balance, the atmosphere would become unsuitable for life, and the energy cycle that sustains all living organisms would cease.
In simple words: Photosynthesis makes oxygen and takes in carbon dioxide, while respiration uses oxygen and gives out carbon dioxide. These two processes keep the air clean and make sure all living things have the right gases and energy to survive, keeping nature balanced.

🎯 Exam Tip: Focus on the complementary nature of these two processes, particularly their roles in the oxygen and carbon cycles, and how they maintain the essential balance of gases in the atmosphere.

Life Processes in Plants Class 7 Questions and Answers (Intext)

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Question 1. How does sunlight contribute in the production of starch in plants?
Answer: Sunlight is extremely important for the production of starch in plants because it provides the **energy** needed for photosynthesis. During photosynthesis, plants use sunlight to convert water and carbon dioxide into glucose, which is a simple sugar. This glucose is the plant's food.
Later, this glucose is converted into starch, which is a complex carbohydrate that plants store as a long-term energy reserve. Without sunlight, plants cannot make glucose, and therefore, they cannot produce or store starch. Sunlight acts as the power source for the entire food-making process.
In simple words: Sunlight gives plants the energy they need to make sugar from water and air. This sugar then turns into starch, which the plant keeps for energy. Without sunlight, no starch is made.

🎯 Exam Tip: Remember that sunlight is the primary energy source for photosynthesis. Without it, the chemical reactions that produce glucose (and subsequently starch) cannot take place.

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