Class VII – Science

Chapter 1: Nutrition in Plants

I. Fill in the blanks

1. The process of intake of food and its proper utilization by the body is called nutrition.
2. Two modes of nutrition in plants are autotrophic and heterotrophic.
3. The mode of nutrition in which an organism makes its own food from simple substances like carbon dioxide, water, and minerals present in the surroundings is called autotrophic.
4. All the green plants and some bacteria prepare their own food by autotrophic mode of nutrition.
5. The leaves of a plant are green because they contain tiny green-colored bodies called chloroplasts that contain a green pigment called chlorophyll.
6. The chloroplast uses sunlight to prepare food from carbon dioxide and water.
7. The process by which green plants make their own food from carbon dioxide and water in the presence of sunlight and chlorophyll is called photosynthesis.
8. Complete the photosynthesis reaction: \[ \text{Carbon dioxide} + \text{water} \xrightarrow{\text{A}} \text{C} + \text{D} \] – A: Chlorophyll – B: Sunlight – C: Glucose – D: Oxygen
9. The food prepared by the green leaves of a plant is in the form of a simple carbohydrate called glucose.
10. The extra glucose is changed into a complex carbohydrate called starch, which is also the reserve food material of a plant.
11. The conditions necessary for photosynthesis are sunlight, chlorophyll, carbon dioxide, and water.
12. The chemical used for decolorizing a leaf is alcohol.
13. The process of decolorizing a leaf is known as bleaching.
14. The green color of the plants is due to the presence of the pigment called chlorophyll.
15. In desert plants, like cactus, the leaves are modified into spines to reduce water loss by transpiration.
16. Tiny pores called stomata present on the underside of the leaves, which are surrounded by guard cells.
17. The guard cells control the opening and closing of stomata.
18. Water and minerals are absorbed by the roots of the plants from the soil.
19. Xylem is a tube-like structure found in roots, stem, branches, and leaves that transport water and minerals to the plant.
20. Food is stored in plants in the form of starch.
21. Proteins are substances that contain nitrogen.
22. Plants need nitrogen in a soluble form.
23. Soil has certain bacteria, called nitrogen-fixing bacteria that take atmospheric nitrogen and convert it into compounds like nitrates.
24. Certain plants, like sunflower and soybean, convert glucose into starch and store them in their seeds.
25. The word heterotrophic means feeding on others.
26. The organisms that obtain food prepared by the green plants directly or indirectly are called heterotrophic type of nutrition.
27. The parasitic is a type of nutrition in which some plants live in or on the body of other living organisms.
28. The mode of nutrition of getting nutrients from dead and organic matter of plants and animals is called saprotrophic. Plants that use saprotrophic mode of nutrition are called saprophytes.
29. A lichen is composed of two distinct organisms, algae and fungus that live and work together.
30. Parasitic plants live on other plants called hosts and depend on them for nutrition.
31. The association in which two different types of work together for their mutual benefit is called symbiosis.
32. Rhizobium bacteria live in the nodules of the roots of leguminous plants and provide them nitrogen in a soluble form.
33. Some plants feed on insects to fulfill their nitrogen requirements. These insect-eating plants are called insectivorous.
34. In a pitcher plant, the leaves are modified to form a pitcher-like structure, and the lid is modified into a lid that closes and opens the mouth of the pitchers.
35. Manure and fertilizers are used to replenish the nutrients in the soil.

II. Name the Following

1. Bacteria that lives in the root nodules of the leguminous plants: Rhizobium
2. Two examples of organisms that are saprophytes: Mushrooms, Yeast
3. Name a total parasite and a partial parasite: Cuscuta (Total Parasite), Mistletoe (Partial Parasite)
4. Two examples of organisms that exhibit heterotrophic nutrition: Animals, Fungi
5. Chemical used for the process of bleaching: Alcohol
6. Chemical that tests the presence of starch: Iodine solution
7. Tissue that transports water and minerals in plants: Xylem

III. Analogy Based Questions

1. Xylem: Water and Mineral :: Phloem: Food
2. Dodder: Total Parasite :: Mistletoe: Partial Parasite
3. Lichen: Symbiosis :: Fungi: Saprotrophic

IV. Correct the Underlined Word

1. Oxygen is released during the process of photosynthesis.
2. Parasitic plants live on other plants called hosts and depend on them for nutrition.
3. The food prepared by the green leaves of a plant is in the form of a simple carbohydrate called glucose.

V. Assertion – Reason Based Questions

Use the following key to choose the appropriate answer:

• (a) Both A and R are true and R is the correct explanation of A.
• (b) Both A and R are true but R is not the correct explanation of A.
• (c) A is true but R is false.
• (d) A is false but R is true.

1. Assertion (A): Plants make their food themselves and are called autotrophs.
   Reason (R): Human beings and other animals depend on plants for their food.
   Answer: (a) Both A and R are true and R is the correct explanation of A.
2. Assertion (A): Water and minerals present in the soil are absorbed by roots and transported to leaves.
   Reason (R): Carbon dioxide from air is taken through stomata present on the surface of leaves.
   Answer: (b) Both A and R are true but R is not the correct explanation of A.

VI. Case Study Based Questions

A. Plants synthesize carbohydrates through the process of photosynthesis. The carbohydrates are made up of carbon, hydrogen, and oxygen. These are used to synthesize other components of food such as proteins and fats. But proteins are nitrogenous substances which contain nitrogen.

However, plants cannot absorb nitrogen in this form. Soil has certain bacteria that convert gaseous nitrogen into soluble form and release it into the soil. Also, we might have seen farmers adding fertilizers rich in nitrogen to the soil. In this way, the plants fulfill their requirements of nitrogen along with the other constituents. Plants can synthesize proteins and vitamins.

Besides leaves, photosynthesis also takes place in other green parts of the plant – in green stems and green branches. The desert plants have spine-like leaves to reduce loss of water by transpiration. These plants have green stems which carry out photosynthesis.

1. Carbohydrates are made up of carbon, hydrogen, and oxygen.
2. Protein is a nitrogen-containing compound.
3. Rhizobium organisms convert gaseous nitrogen into a usable form.
4. Desert plants reduce the loss of water by having spine-like leaves.
5. Plants fulfill their nitrogen requirements with the help of nitrogen-fixing bacteria.

VII. Higher Order Thinking Skill Based Questions

1. How do Rhizobium bacteria and leguminous plants help each other in survival?
   Answer: Rhizobium bacteria fix nitrogen from the atmosphere into the soil, making it available for leguminous plants. In return, the plants provide carbohydrates and a habitat for the bacteria.
2. How can you say photosynthesis maintains the balance between oxygen and carbon dioxide in the atmosphere?
   Answer: Photosynthesis absorbs carbon dioxide and releases oxygen, thus maintaining the balance of these gases in the atmosphere.
3. Rohit places a potted plant in a room in complete darkness. After 3 days, he takes out the plant and tests the leaf for the presence of starch. Will he get a positive starch test? Give a reason for the same.
   Answer: No, he will not get a positive starch test because, in the absence of light, photosynthesis cannot occur, and thus no starch is produced.
4. Radharamana is a farmer. He always alternates two wheat crops with a leguminous crop. Why?
   Answer: Alternating wheat crops with leguminous crops helps in replenishing the nitrogen content in the soil due to the nitrogen-fixing ability of leguminous plants.
5. The lamina of the leaf of a plant P is modified into a hollow tube. The leaf apex forms a lid that can open or close the mouth of the hollow tube. When organism Q falls into the hollow tube, the lid closes automatically, killing the organism. The walls of the hollow tube secrete digestive juices which digest the complex substances R present in the body of the organism to form simpler substances S. These simple substances are then absorbed by the walls of the hollow tube and used by the plant P.
   1. What could the plant P be?
      Answer: The plant P could be a pitcher plant.
   2. Name the organism Q.
      Answer: The organism Q could be an insect.
   3. What could the complex substances R be?
      Answer: The complex substances R could be proteins.
   4. Name the simpler substances S.
      Answer: The simpler substances S could be amino acids.
   5. What is the general name of plants like P?
      Answer: The general name of plants like P is insectivorous plants.
6. Two different species of plants X and Y live together as if they are parts of the same plant Z. The plant X is an autotroph whereas plant Y is a saprophyte. The plant Y holds the cells of X in its mat of web-like hyphae and supplies water and minerals to the cells of plant X. The plant X makes food by photosynthesis and shares it with plant Y.
   1. What could plants (i) X, (ii) Y, and (iii) Z be?
      Answer: (i) Plant X could be algae, (ii) Plant Y could be fungus, and (iii) Plant Z could be lichen.
   2. Which of the two plants X or Y is green in color?
      Answer: Plant X (algae) is green in color.