NCERT Solutions for Class 7 Science Chapter 1 Nutrition In Plants

Q.1 Why do organisms need to take food?

Answer :

1.All organisms require energy for their life process which they get from food.
Thus food is essential for all organisms.

2.Carbohydrates, proteins, fats, vitamins, and minerals are components of food.
These components of food are called nutrients and are necessary for our bodies.

3.Plants can synthesize food for themselves and acquire nutrients from abiotic components
but animals including humans cannot. They get it from plants or animals that eat plants.
Thus, humans and animals are directly or indirectly dependent on plants.

Q.2 Distinguish between a parasite and a saprophyte.

Answer :

Parasite:

1.Organisms that derive nutrition from the body of other living organisms(host) are called parasites.
2.They harm the source either by creating an infection or consuming its blood.
3.They take the ready-made food from the host.
4.They don't help in cleaning the environment.
Example: Roundworm


Saprophyte:

1.Organisms that derive nutrition from dead and decaying matter are called saprotrophs.
2.It doesn't harm the source as the source is already dead.
3.They take the ready-made food from the host.
4.They help in cleaning the environment as they feed on dead and decaying matter.
Example: Fungi

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

Answer :

The presence of starch in leaves can be tested by the Iodine test.

1.Take two potted plants of the same kind- for example, money plants or crotons.
2. Keep one in the dark for 72 hours and the other in sunlight.
3. Perform the iodine test with the leaves of both plants.
Iodine test-To put iodine solution on the leaf.
4.Now leave the pot which was earlier kept in the dark, undisturbed for 3 – 4 days,
and perform the iodine test again on its leaves.

Observation:

1.Blue-black color will be observed on the leaves of the plant kept in sunlight,
which indicates the presence of starch.
2.Blue-black color will not be observed on the leaves of plants kept in the darkroom.
This indicates the absence of starch.

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

Answer :

(1) Leaves are the food factories of plants.
Therefore, all the raw materials must reach the leaf.

(2) Water and minerals present in the soil are absorbed by the roots and
transported to the leaves by the vessels.

(3)Carbon dioxide from air is taken in through the tiny pores present
on the surface of leaves called 'stomata'.

(4) The leaves have a green pigment called chlorophyll which helps leaves to capture
the energy of the sunlight.
This energy is used to synthesize (prepare) food from carbon dioxide and water.

(5)Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis.
So we find that chlorophyll, sunlight, carbon dioxide, and water are necessary to carry out the process of photosynthesis.

(6) During photosynthesis, chlorophyll-containing cells of leaves, in the presence of sunlight, use carbon dioxide and water to synthesize carbohydrates.
The process can be represented in an equation:

Carbon dioxide + water → Carbohydrate + oxygen

During the process, oxygen is released.
The presence of starch in leaves indicates the occurrence of photosynthesis.

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 → Leaf
Nitrogen → Rhizobium
Cuscuta → 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 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 the external climatic condition and provides
suitable temperature for the growth of crops.

Advantages to farmers while growing fruits and vegetable crops inside greenhouses are:

(1)It protects crops from diseases and adverse climatic conditions.
(2)It protects crops from wind and rodents.
(3)Farmers have bountiful crops.
(4)Farmer's crops are also protected from birds and animals.