NCERT Solutions for Class 7 Science Chapter 1 Nutrition in Plants

Class 7 Science Chapter 1:- Chapter 1 of Class 7 Science, titled "Nutrition in Plants," introduces students to how plants obtain and use their nutrients. It explains the concept of nutrition, the different ways plants get their food, and the process of photosynthesis, where green plants make food using sunlight, water, and carbon dioxide. The chapter also covers other methods of nutrition, like parasitism and saprotrophism, showing how plants adapt to their surroundings to meet their nutritional needs. Go through the NCERT Solutions for Class 7 Science Chapter 1 Nutrition in Plants here.

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Nutrition in Plants Class 7

Get the class 7 science chapter 1 question answer below:-

1. Why do organisms take food?

Solution: All organisms require energy to perform various life processes such as growth, reproduction, movement, and maintenance of bodily functions. Plants, being autotrophs, have the unique ability to synthesise their food through the process of photosynthesis, utilising sunlight, water, carbon dioxide, and nutrients from the soil. This allows them to produce the necessary energy and nutrients required for their survival.

On the other hand, animals, which are heterotrophs, cannot produce their food. They must consume other organisms, either plants or other animals, to obtain the nutrients and energy needed for their bodily functions. This energy is crucial for metabolic processes, maintaining body temperature, and supporting the growth and repair of tissues. Thus, all organisms take food to acquire the essential nutrients and energy needed for their survival and proper functioning.

2. Distinguish between a parasite and a saprophyte.

Solution: 

3. How would you test the presence of starch in leaves?

Solution:

To test the presence of starch in leaves, the following experiment can be conducted:

1. Preparation: Take two potted plants of the same species. Keep one plant in complete darkness for 72 hours to deplete the starch reserves in its leaves, while the other plant should be kept in sunlight.

2. Iodine Test:

• Pluck a leaf from each plant.

• Boil the leaves in water for a few minutes to kill them, making them more permeable.

• Then, place the leaves in alcohol (preferably ethanol) and heat them in a water bath until they become decolourized, which removes the chlorophyll.

• After decolourization, wash the leaves with warm water to soften them.

• Place a few drops of iodine solution on each leaf.

3. Observation:

• The leaf from the plant that was kept in sunlight will turn blue-black, indicating the presence of starch, which is a product of photosynthesis.

• The leaf from the plant that was kept in darkness will not change colour, indicating the absence of starch, as the plant could not perform photosynthesis without sunlight.

4. Give a brief description of the process of synthesis of food in green plants.

Solution: Green plants synthesize their food through a process called photosynthesis, which primarily occurs in the leaves. This process is essential for the survival of plants and, by extension, all life forms that depend on plants for food.

• Water Uptake: The roots of the plant absorb water from the soil. This water is then transported through the plant's vascular system to the leaves, where photosynthesis occurs.

• Carbon Dioxide Absorption: Carbon dioxide from the atmosphere enters the leaves through small openings called stomata. Once inside the leaf, the carbon dioxide diffuses into the cells containing chloroplasts, which are the sites of photosynthesis.

• Light Absorption and Splitting of Water: Chlorophyll, the green pigment in chloroplasts, absorbs sunlight, which provides the energy needed to split water molecules into hydrogen and oxygen.

• Formation of Carbohydrates: The hydrogen produced from the splitting of water molecules combines with carbon dioxide in a series of reactions known as the Calvin cycle to form glucose (a simple carbohydrate). Oxygen is released as a by-product during this process.

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5. Show with the help of a sketch that plants are the ultimate source of food.

Solution:

A sketch depicting a simple food chain can illustrate that plants are the ultimate source of food. For example:

• Sunlight → Plant (Producer) → Herbivore (Primary Consumer) → Carnivore (Secondary Consumer)

In this food chain, the plant, which is the producer, synthesizes its food using sunlight through photosynthesis. Herbivores, such as deer or cows, consume the plants to obtain energy. Carnivores, such as lions or wolves, then feed on the herbivores. This shows that the energy and nutrients originally come from plants, making them the ultimate source of food for all organisms in the food chain.

6. Fill in the blanks.

(a) Green plants are called _________________ since they synthesise their food.

(b) The food synthesised by plants is stored as _________________.

(c) In photosynthesis, solar energy is absorbed by the pigment called ___________.

(d) During photosynthesis, plants take in ______________________ and release __________________ gas.

Solution:

(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.

7. Name the following.

i) A parasitic plant with a yellow, slender and branched stem.

ii) A plant that is partially autotrophic.

iii) The pores through which leaves exchange gases.

Solution:

i) Cuscuta: A parasitic plant with a yellow, slender, and branched stem.

Cuscuta, commonly known as dodder, is a parasitic plant that lacks chlorophyll and relies entirely on a host plant for its nutrients. It attaches itself to the host using specialized structures called haustoria, through which it extracts water and nutrients.

ii) Pitcher plant: A plant that is partially autotrophic.

The pitcher plant is an insectivorous plant that can photosynthesize but also traps and digests insects to obtain additional nutrients, especially in environments where the soil is deficient in nitrogen.

iii) Stomata: The pores through which leaves exchange gases.

Stomata are small openings on the surface of leaves that facilitate gas exchange. They allow carbon dioxide to enter the leaf for photosynthesis and oxygen to exit as a by-product. They also play a role in transpiration, the process by which water vapor is released from plants.

8. 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

(iii) pitcher plant

(iv) rose

Solution:

(a) Cuscuta is an example of:

(i) autotroph
(ii) parasite
(iii) saprotroph
(iv) host

Cuscuta is a parasitic plant that depends on other plants for its nourishment. It lacks chlorophyll and, therefore, cannot perform photosynthesis on its own.

(b) The plant which traps and feeds on insects is:

(i) Cuscuta
(ii) China rose
(iii) pitcher plant
(iv) rose

The pitcher plant is an example of an insectivorous plant that traps and digests insects. This adaptation helps it survive in nutrient-poor soils where nitrogen is scarce.

9. Match the items given in Column I with those in Column II.

Solution:

• Chlorophyll → Leaf: Chlorophyll is found in the chloroplasts of leaf cells and is responsible for the green color of leaves and the absorption of light energy for photosynthesis.

• Nitrogen → Rhizobium: Rhizobium is a nitrogen-fixing bacterium that lives in the root nodules of leguminous plants and converts atmospheric nitrogen into a form usable by the plant.

• Cuscuta → Parasite: Cuscuta is a parasitic plant that derives its nutrients from other plants.

• Animals → Heterotrophs: Animals are heterotrophs, meaning they cannot produce their food and must obtain it by consuming other organisms.

• Insects → Pitcher plant: The pitcher plant is an insectivorous plant that traps and digests insects to supplement its nutrient intake.

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10. Mark ‘T’ if the statement is true and ‘F’ if it is false.

Solution:

(a) Carbon dioxide is released during photosynthesis. (F)

(b) Plants that synthesize their food are called saprotrophs. (F)

(c) The product of photosynthesis is not a protein. (T)

(d) Solar energy is converted into chemical energy during photosynthesis. (T)

11. Choose the correct option from the following:

Solution:

Which part of the plant gets carbon dioxide from the air for photosynthesis?

(i) Root hair
(ii) Stomata
(iii) Leaf veins
(iv) Sepals

The correct answer is Stomata. Stomata are small openings on the surface of leaves that allow the exchange of gases, including the intake of carbon dioxide necessary for photosynthesis.

Class 7 Science Chapter 1 Summary

Chapter 1 of Class 7 Science, "Nutrition in Plants," covers the essential concepts related to how plants obtain and utilize nutrients. The chapter begins by explaining the need for nutrition in plants and introduces the concept of autotrophic nutrition, where plants make their own food through photosynthesis. It details the process of photosynthesis, where green plants use sunlight, carbon dioxide, and water to produce glucose and oxygen, with the help of chlorophyll.

The chapter also explores alternative modes of nutrition in plants, such as parasitism and saprotrophism. It explains how certain plants, like the Cuscuta (a parasitic plant), depend on other living plants for their nutrition. Similarly, saprophytes, like fungi, obtain nutrients from decaying organic matter.

The importance of nutrients in the soil and how they are replenished, particularly nitrogen, is also discussed. The role of bacteria, such as Rhizobium, in converting atmospheric nitrogen into a usable form for plants is highlighted.

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Class 7 Science Chapter 1 FAQs

Q1. What is autotrophic nutrition?

Ans. Autotrophic nutrition is the process by which green plants and some other organisms produce their own food using sunlight, carbon dioxide, and water through the process of photosynthesis.

Q2. What is photosynthesis, and why is it important?

Ans. Photosynthesis is the process by which green plants use sunlight, carbon dioxide, and water to produce glucose (a type of sugar) and oxygen. It is crucial because it is the primary way that energy from the sun is converted into chemical energy in food, supporting life on Earth.

Q3. What role does chlorophyll play in photosynthesis?

Ans. Chlorophyll is the green pigment in plant leaves that absorbs sunlight, which provides the energy needed for photosynthesis to take place.