Welcome to the page on "Nutrition in Plants" for Class 7! In this comprehensive guide, you will find all the essential information and questions related to the chapter "Nutrition in Plants" from the Class 7 CBSE.
Q1.Why do organisms take food?
Answer:- organisms take food to obtain energy, support growth and development, repair and maintain their bodies, carry out metabolic processes, ensure survival, and facilitate reproduction.
Q2. Distinguish between a parasite and a saprotroph.
| Parasite | Saprotroph |
|---|---|
| A parasite is an organism that lives in or on another organism (host) and obtains its nutrients from the host. | A saprotroph is an organism that obtains nutrients by decomposing dead organic matter. |
| Parasites depend on the host for their survival and reproduction. | Saprotrophs feed on dead or decaying organic material, such as dead plants, animal remains, or organic waste. |
| Parasites derive nutrients from the host's body fluids or tissues, often causing harm or damage to the host. | They secrete enzymes to break down complex organic compounds into simpler substances, which they absorb as nutrients. |
| Examples: Fleas, ticks, lice, tapeworms, and parasitic plants like mistletoe. | Fungi (like mushrooms), certain bacteria, and some types of insects, such as dung beetles. |
Q3. How would you test the presence of starch in leaves?
Answer:- To test the presence of starch in leaves, you can perform the following steps:
1. Collect a fresh leaf from a plant and ensure it has been exposed to sunlight for a few hours.
2. Boil the leaf in water for a few minutes. This process helps soften the leaf and break down the cell walls.
3. Transfer the boiled leaf to a test tube or a small beaker containing ethanol (alcohol) and place it in a water bath. The ethanol will remove the chlorophyll, making it easier to observe the presence of starch.
4. Place the test tube or beaker in a boiling water bath for a few minutes. The heat will accelerate the process of removing chlorophyll and dissolve any remaining pigments.
5. Carefully remove the leaf from the ethanol and rinse it with water to remove excess ethanol.
6. Apply a few drops of iodine solution onto the leaf. Iodine solution reacts with starch and produces a color change, typically from brownish-yellow to blue-black or dark purple.
7. Observe the leaf for any color change. If the leaf turns blue-black or dark purple, it indicates the presence of starch. If there is no color change, it suggests the absence of starch.
It's important to note that this test confirms the presence of starch, which is a product of photosynthesis in plants. Starch acts as a storage form of energy.
Q4.Give a brief description of the process of synthesis of food in green plants
Answer:- The process of synthesizing food in green plants is called photosynthesis. It is a complex biochemical process that involves the conversion of light energy from the sun into chemical energy in the form of glucose (food). Here is a brief description of the process:
1. Absorption of sunlight: Green plants have a pigment called chlorophyll in their chloroplasts, which enables them to capture sunlight. Chlorophyll absorbs light energy.
2. Plants obtain water from the soil through their roots, and carbon dioxide from the atmosphere through tiny openings called stomata present on their leaves.
3. Inside the chloroplasts, the light energy is used to convert water (H2O) and carbon dioxide (CO2) into glucose (C6H12O6)
4. As a byproduct of photosynthesis, oxygen (O2) is released into the atmosphere.
5.The synthesized glucose serves as the primary source of energy for the plant. It is either used immediately for various metabolic processes or stored as starch for future energy needs.
Photosynthesis is an essential process not only for plants but also for the overall balance of the ecosystem. It plays a crucial role in the oxygen-carbon dioxide cycle and provides the foundation of the food chain, as other organisms depend on plants for their energy requirements.
Q5. Fill in the blanks.
(a) Green plants are called autotrophs since they synthesize their own food.
(b) The food synthesized by plants is stored as starch.
(c) In photosynthesis, solar energy is absorbed by the pigment called chlorophyll.
(d) During photosynthesis, plants take in carbon dioxide and release oxygen gas.
Q.6 Name the following:
(i) A parasitic plant with yellow, slender, and branched stem: Cuscuta (Dodder)
(ii) A plant that is partially autotrophic: Epiphytes (such as Orchids)
(iii) The pores through which leaves exchange gases: Stomata
Q7. Tick the correct answer:
(a) Cuscuta is an example of:
(i) autotroph (ii) parasite (iii) saprotroph (iv) host
(b) The plant which traps and feeds on insects is:
(i) Cuscuta (ii) china rose (iv) pitcher plant (iv) rose
Q.8 Match the items given in Column I with those in Column II:
| Column I | Answer |
|---|---|
| Chlorophyll | Leaf |
| Nitrogen | Rhizobium |
| Cuscuta | Parasite |
| Animals | Heterotrophs |
| Insects | Pitcher plant |
Q9. Mark ‘T’ if the statement is true and ‘F’ if it is false:
Answer:-
(i) Carbon dioxide is released during photosynthesis. (F)
(ii) Plants which synthesise their food are called saprotrophs. (F)
(iii) The product of photosynthesis is not a protein. (T)
(iv) Solar energy is converted into chemical energy during photosynthesis. (T)
Q10. Choose the correct option from the following:
Which part of the plant takes in carbon dioxide from the air for
photosynthesis?
(i) Root hair (ii) Stomata (iii) Leaf veins (iv) Petals
(The correct option is (ii) Stomata. Stomata are small openings or pores present on the surface of leaves, primarily on the underside. They allow for the exchange of gases, including the uptake of carbon dioxide (CO2) from the air and the release of oxygen (O2) produced during photosynthesis.)
Q11. Choose the correct option from the following:
Plants take carbon dioxide from the atmosphere mainly through their:
(i) roots (ii) stem (iii) flowers (iv) leaves
Q12. Why do farmers grow many fruits and vegetable crops inside large green houses? What are the advantages to the farmers?
Answers:- Farmers grow many fruits and vegetable crops inside large greenhouses for several reasons, and there are several advantages for the farmers:
1. Greenhouses provide a controlled environment that allows farmers to extend the growing season beyond the natural limitations of the climate. This means they can grow crops throughout the year, regardless of the external weather conditions.
2. Greenhouses offer protection from extreme weather events such as frost, hail, heavy rain, or strong winds. This protection reduces the risk of crop damage and allows for more consistent and reliable yields.
3. Greenhouses act as a barrier against pests, insects, and diseases, reducing the likelihood of crop damage and the need for chemical pesticides. The enclosed environment makes it easier to monitor and manage pests and diseases effectively.
4. The controlled environment inside greenhouses enables farmers to optimize growing conditions such as temperature, humidity, and light intensity. This leads to better crop quality, including improved flavor, color, texture, and overall appearance.
5. With precise control over environmental factors, farmers can create optimal growing conditions for crops. This often results in higher yields compared to open-field cultivation. Greenhouses provide an opportunity to maximize productivity and harvest more crops per unit of land.
6. Greenhouses facilitate efficient water management through techniques like drip irrigation and recycling systems. This reduces water wastage and makes more efficient use of this valuable resource.
7. Growing crops in a controlled environment minimizes weed growth, reducing the competition for nutrients, water, and light. This simplifies weed management and reduces the need for manual labor or herbicides.
8. Greenhouses offer flexibility in crop selection, allowing farmers to grow a wide range of fruits and vegetables that may not be suitable for the local climate. This opens up opportunities to diversify crops and meet the demands of specific markets.
Overall, growing fruits and vegetables in large greenhouses provides farmers with greater control, protection, and opportunities for higher productivity and profitability.
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