NCERT Solutions for Class 7 Science Chapter 1 Nutrition In Plants

Q.1 Why do organisms need to take food?

Answer :

All living organisms require food to survive. It gives them energy to perform various activities. All activities such as playing, running, walking, studying, etc. require energy. The various components present in our food such as carbohydrates, proteins, fats, vitamins, and minerals provide energy to our body. These are also important for growth and development of the body.

Q.2 Distinguish between a parasite and a saprophyte.

Answer :

Parasite: Parasites live on or in a host and get its food at the expense of its host
Saprophyte: a plant, fungus, or microorganism that lives on dead or decaying organic matter.

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

Answer :

Experiment to test the presence of starch in leaves
Take two healthy green potted plants of the same type. Keep one potted plant in a dark room for one or two days in order to remove all the starch from the leaves. Keep the other plant in sunlight. Now, take one leaf from each potted plant and put a few drops of iodine solution on them. Then note down the observation.
Plants kept in light and dark conditions
No blue black colour will be observed on the leaves of the plant kept in the dark room. This indicates the absence of starch. Blue black colour will be observed on the leaves of the plant kept in sunlight. This indicates the presence of starch.

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

Answer :

(a) Water is taken in from the roots of the plant and is transported to the leaves.
(b) Carbon dioxide from the air enters the leaves through the tiny pores called stomata and diffuses to the cells containing chlorophyll.
(c) Solar energy is used to break water into hydrogen and oxygen. This hydrogen is combined with carbon dioxide to form food for the plants, which is ultimately used by the animals as well. Thus, photosynthesis can be represented by the following equation.
Carbon dioxide + water $?$ Carbohydrate + oxygen

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

Answer :

Q.6 Fill in the blanks:
(a) Green plants are called _________________ since they synthesise their own 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.

Answer :

(a) Green plants are called __autotrophs__ since they synthesise their food.
(b) The food synthesised 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.7 Name the following:
i) A parasitic plant with yellow, slender and branched stem.
ii) A plant that is partially autotrophic.
iii) The pores through which leaves exchange gases.

Answer :

i) Cuscuta
ii) Pitcher plant
iii) Stomata

Q.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

Answer :

(a) (ii) Parasite
(b) (iii) Pitcher plant

Q.9 Match the items given in Column I with those in Column II:
Column- I. Column-II
Chlorophyll. Rhizobium
Nitrogen. Heterotrophs
Cuscuta. Pitcher plant
Animals. Leaf
Insects. Parasite

Answer :

Column- I. Column-II
Chlorophyll. \(\rightarrow )Leaf
Nitrogen\(\rightarrow )Rhizobium
Cuscuta. \(\rightarrow ) Parasite
Animals\(\rightarrow )Heterotrophs
Insects\(\rightarrow )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 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)

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)

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) Petals

Answer :

(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

Answer :

(iv) leaves

Q.13 Why do farmers grow many fruits and vegetable crops inside large green houses? What are the advantages to the farmers?

Answer :

Fruits and vegetable crops are grown in large greenhouses because it protects crops from external climatic condition and to provide suitable temperature for the growth of crops.
Advantages to farmers while growing fruits and vegetable crops inside greenhouses are
It protects crops from diseases and adverse climatic conditions.
It protects crops from wind and rodents