Nutrition In Plants

Science Class Seven

Solution of NCERT Questions

Question (1) Why do organism need to take food?

Answer

The nutrients enable living organisms to build their bodies, to grow, to repair damaged parts of their bodies and provide the energy to carry out life processes.

Since organism get the nutrients from food, thus organisms need to take food.

Question (2) Distinguish between a parasite and a saprotroph.

Answer:

Parasites grow and feed on other green plants, such as cuscuta while saprotrophs grow and feed on dead and decaying organisms such as fungi.

Parasites get nutrition made by host on which they feed while saprotrophs secrete digestive juices on dead and decaying matter and convert it into a solution then they absorb the nutrients from it.

The mode of nutrition in parasites is known as heterotrophic nutrition while the mode of nutrition in saprotrophs is called saprotrophic nutrition.

Question (3) How would you test the presence of starch in leaves?

Answer

The presence of starch in leaves can be test using iodine test.

Steps to perform test:

(a) Green leaf is taken and boiled in water for about 5 minutes.

(b) After leaf is boiled in alcohol over water bath.

(c) Then boiled leaf is washed using cold water.

(d) After washing leaf is spread on a glass.

(e) After that few drops of iodine is poured on leaf.

(f) The turn of iodine drops into dark blue colour confirms the presence of starch in leaf.

Question (4) Give brief description of the process of synthesis of food in green plants.

Answer

For the photosynthesis, sunlight, chlorophyll, carbon dioxide and water is necessary.

Green plants have green leaves. Chlorophyll is found in green leaves of plant.

In the presence of sunlight, leaves take carbon dioxide from air and take water from soil.

Leaves take energy from sunlight and use carbon dioxide and water to synthesise food. In this process leaves synthesise carbohydrate and release oxygen. Carbohydrate is finally converted into starch.

Reaction involve in the process of photosynthesis:

Carbon dioxide + Water + Chlorophyll + sunlight ⇒ Carbohydrate + Oxygen.

The synthesized food then stored as starch in leaves, stem, root and fruit of plants.

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

Answer

Only green plants synthesise their food by the process of photosynthesis. Animals including human do not make their food. They take readymade food prepared by plants. Animals including human either eats plants or plant eating animals.

Plants ⇒ Plant eating Animals ⇒ Animal

Plants ⇒ Animals

Since, animals including human and other organism depend directly or indirectly on plants, thus, plants are the ultimate source of food.

Question (6) Fill in the blanks:

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

Answer Green plants are called Autotrophs since they synthesise their own food.

(b) The food synthesized by the plants is stored as __________.

Answer The food synthesized by the plants is stored as starch.

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

Answer: In photosynthesis solar energy is captured by the pigment called Chlorophyll.

(d) During photosynthesis plants take in ________ and release ________.

Answer: During photosynthesis plants take in Carbon dioxide and release Oxygen.

Question (7) Very short Answer type questions

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

Answer : Cuscuta

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

Answer: Pitcher plants.

(iii) The pores through which leaves exchange gases.

Answer: Stomata.

Question (8) Tick the correct answer:

(a) Amarbel is an example of :

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

Answer: (ii) parasite

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

(i) Cucuta (ii) China rose (iii) Pitcher plant (iv) rose

Answer: (iii) Pitcher plant

Question (9) Match the items given in column I with those in column II

Column IColumn II
ChlorophyllBacteria
NitrogenHeterotrophs
AmarbelPitcher plant
AnimalsLeaf
InsectsParasite

Answer

Column IColumn II
ChlorophyllLeaf
NitrogenBacteria
AmarbelParasite
AnimalsHeterotrophs
InsectsPitcher plant

Question (10) Mark 'T' if the statement is true and 'F' is it is false:

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

Answer: F

Explanation: True statement: Oxygen is released during photosynthesis.

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

Answer: F

Correct statement: Plants which synthesise their food themselves are called autotrophs.

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

Answer: T

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

Answer: T

Question (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

Answer: (ii) Stomata

Question (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

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