NCERT Solutions Class 7 Science Chapter 1 Nutrition in Plants

NCERT Solutions for Class 7 Science for chapter 1 Nutrition in Plants

Q.1 Why do organisms need to take food?

Ans. 1 Organisms take food to meet their requirements of nutrients and energy. Nutrients and energy enable the organisms to grow, reproduce and repair their damaged body parts.

Q.2 Distinguish between a parasite and a saprotroph.

Ans. 2 A parasite derives nutrition from the body of a living host by invading its tissues whereas, a saprotroph derives its nutrition from dead and decaying organic matter.

Examples of parasite: Cuscuta and leech

Examples of saprotrophs: Fungi and bacteria

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

Ans. 3 The presence of starch in the leaves can be tested with the help of iodine solution that gives blue- black colour with starch. Boil few green leaves in alcohol in a test tube till they turn colourless or pale green. Then wash the leaves in tap water and transfer them into a petridish. Add some drops of iodine. A change in colour of leaves to blue-black indicates the presence of starch in them.

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

Ans. 4 The leaves of green plants contain chlorophyll pigment which traps solar energy. This energy is utilized by the leaves for the synthesis of organic food from water and carbon dioxide. Water is absorbed by the roots and carbon dioxide is taken up from the atmosphere through the tiny pores called stomata. Thus, sunlight, chlorophyll, water and carbon dioxide are the important raw materials required for photosynthesis.

The process of photosynthesis can be summarised as follows:

Sunlight

CO₂ + H₂O    -> Sunlight/Chlorophyll->          C₆H₁₂O₆ + O₂

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

Ans. 5 The following diagram depicts the synthesis of carbohydrates or glucose by the green plants in the presence of sunlight and the transfer of energy to herbivores and then, to carnivores on consumption:

 

Explanation: In this food chain we observe that carnivores like lions depend on herbivores for food and energy. A herbivore gets it food and energy by consuming plants. Plants manufacture their food with the help of sunlight. Thus herbivores and carnivores are all directly or indirectly dependent on plants for food.

Q.6 Fill in the blanks:

(a) Green plants are called________ since they synthesise their own food.

(b) The food synthesised by the plants is stored as_________.

(c) In photosynthesis solar energy is captured by the pigment called______.

(d) During photosynthesis plants take in_______and release________.

Ans. 6

(a) Autotrophs

(b) Starch

(c) Chlorophyll

(d) Carbon dioxide, Oxygen

Q.7 Name the following:

(i) A parasitic plant with yellow, slender and tubular stem.

(ii) A plant that has both autotrophic and heterotrophic modes of nutrition.

(iii) The pores through which leaves exchange gases.

Ans. 7

(a) Cuscuta

(b) Pitcher plant

(c) Stomata

Q.8 Tick the correct answer:

(a) Amar bel 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

Ans. 8 (a) Amarbel is an example of: (ii) parasite

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

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

Column I	Column II
Chlorophyll	Bacteria
Nitrogen	Heterotrophs
Amarbel	Pitcher plant
Animals	Leaf
Insects	Parasite

Ans. 9 The correctly matched contents of Column I and

Column II are as follows:

Column I	Column II
Chlorophyll	Leaf
Nitrogen	Bacteria
Amarbel	Parasite
Animals	Heterotrophs
Insects	Pitcher plant

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

(i) Carbon dioxide is released during photosynthesis. (T/F)

(ii) Plants which synthesise their food themselves are called saprotrophs. (T/F)

(iii) The product of photosynthesis is not a protein. (T/F)

(iv) Solar energy is converted into chemical energy during photosynthesis. (T/F)

Ans. 10

(i) False (ii) False (iii) True (iv) True

Q.11 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) Sepals

Ans. 11 (ii) stomata

Q.12 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

Ans. 12 (iv) leaves