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Question Answers

Q 1 Why is the colour of blood red ? (Page 121)
Ans. Because blood contains a red pigment called haemoglobin.
Q.2 Paheli wonders which side of the heart will have oxygen- rich blood and which side will have carbon dioxide- rich blood. (Page 124)
Ans. Right side of heart has oxygen-rich blood and left side of heart has carbon dioxide-rich blood.
Q.3 Paheli wants to know whether other animals also urinate ? (Page 127)
Ans. Yes.
Q.4 Boojho wants to know why plants absorb a large quantity of water from the soil, then give it off by transpiration.
Ans. Because transpiration helps in suction of water.
NCERT TEXTBOOK EXERCISE           (Page 131-132)
Q.1 Match structures given in column I with functions given in column II.
   Column I.                                 Column II
(i) Stomata                 (a) Absorption of water
(ii) Xylem                   (b) Transpiration 
(iii) Root hairs            (c) Transport of food
(Iv) Phloem                (d) Transport of water
                                    (e) Synthesis of carbohydrates.
Ans. (i) (b); (ii) (d); (iii)(a); (iv) (c).
Q.2 Fill in the blanks:
(i) The blood from the heart is transported to all parts of the body by the……..
(ii) Haemoglobin is present in……..cells.
(iii) Arteries and veins are joined by a network of….
(iv) The rhythmic expansion and contraction of the heart is called……..
(v) The main excretory product in human beings is…………
(vi) Sweat contains water and……..
(vii) Kidneys eliminate the waste materials in the liquid form called……..
(viii) Water reaches great heights in the trees because of suction pull caused by……….
Ans. (i) arteries; (ii) red blood; (iii) capillaries; (iv) heart beat ;(v) urine; (vi) urea; (vii) urine; (vii) transpiration.
Q.3 Choose the correct option :
(i) In, plants, water is transported through :
(a) xylem (b) phloem (c) stomata (d) Root hair.
(ii) Water absorption through roots can be increased by keeping the plants :
(a) in the shade    (b) in dim light 
(c) under the fan  (d) covered with a polythene bag.
Ans. (i) (a); (ii) (b).
Q.4 Why is transport of materials necessary in a plant or in an animal ? Explain.
Ans. Transport of materials is necessary in a plant or animal because due to it, the nutrients are made available to all the parts of the body. If the transport of necessary nutrients does not take place in the body, the body will not be able to survive. For example, in plants roots absorb water, and leaves prepare food utilising the water. The food is also required by root. So, there is no utility of water absorbed by the roots if it does not reach to the leaf or food prepared by leaf if it does not reach to the root. Thus, the process of transportation is necessary.
Q.5 What will happen if there are no platelets in the blood ?
Ans. The blood platelets are responsible for the clotting of the blood. Without the platelets, blood cannot clot. So, if there is any cut, blood will continue to flow and ultimately the person will die.
Q.6 What are stomata ? give two functions of stomata.
Ans. The small pores in leaves and stems of plants are called stomata.
Functions of stomata : 
(i) It absorbs oxygen from air.
(ii) It helps in the transportation of water.
Q.7 Does transpiration serve any useful function in the plants ? Explain.
Ans. Yes, transpiration is an important function in plants. Plants absorb mineral nutrients and water from the soil. All the absorbed water is not utilised by the plants. The water evaporates through the stomata present on the surface of the leaves by the process of transpiration. The evaporation of water from leaves generates a suction pull (the same that you produce when you are suck water through a straw) which can pull water to great heights in the tall trees. Transpiration also cools the plant.
Q.8 What are the components of blood?
Ans. Red Blood Cells (RBC), White Blood Cells (WBC), plasma and platelets are the components of blood.
Q.9 Why is blood needed by all the parts of a body?
Ans. Blood is needed by all the parts of a body because it carries digested food and oxygen to all parts of body. It also carries away the waste products.
Q.10 What makes the blood look red ?
Ans. A red coloured pigment called haemoglobin gives the blood red colour.
Q.11 Describe the function of the heart.
Ans. The main function of heart is to collect the distributes blood from and to all parts of the body.
The right auricle and ventricle receives blood with carbon dioxide from all the parts of the body. The collected blood is then pumped to the lungs for the purification. In lungs, the exchange of gases take place and the purified blood is sent back to the left auricle after that, purified blood is sent to all the parts of the body through arteries.
Q.12 Why is it necessary to excrete waste products?
Ans. waste products are harmful for the body and it is not possible to survive if they are not excreted from our body. So, it is very necessary to excrete them.
Q.13 Draw a diagram of the human excretory system and label the various parts.
Fig. Human excretory system.

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