Before trying to answer the NCERT exercise questions, you should have a thorough understanding of class 7 Science chapter 6 i.e. ‘Respiration in Organism‘.
If you haven’t understood the chapter yet, then worry not you can go through it easily and develop a crystal clear understanding of various concepts from our notes whose link has been provided below. ⤵️
NCERT Exercise Questions & Answers
Que. 1 Why does an athlete breathe faster and deeper than usual after finishing the race?
Ans. 1 While running the body requires a lot of energy for which it needs a large amount of oxygen for respiration but the amount of oxygen available in the body/bloodstream is not sufficient enough. So an athlete starts to breathe faster and deeper to inhale more and more oxygen so this increased energy need can be fulfilled and a very small amount of lactic acid forms in our muscles. Panting after finishing the race provides the body with the oxygen that it requires to completely break down the formed lactic acid.
Que. 2 List the similarities and differences between aerobic and anaerobic respiration.
Ans. 2 The similarities between aerobic and anaerobic respiration are:
- In both kinds of respiration, the glucose or food is broken down to produce energy.
- In both kinds of respiration, carbon dioxide gas is produced.
- Both take place inside the cell.
The differences between aerobic and anaerobic respiration are:
| Aerobic Respiration | Anaerobic Respiration |
| It occurs in the presence of oxygen. | It occurs in the absence of oxygen. |
| More energy is produced in this kind of respiration. | Less energy is produced in this kind of respiration. |
| The end products are CO2 and H2O | The end products are alcohol and CO2 |
| It occurs mainly in higher organisms like plants and animals | It occurs in organisms like yeasts and other bacteria |
Que. 3 Why do we often sneeze when we inhale a lot of dust-laden air?
Ans. 3 When we inhale a lot of dust-laden particles we sneeze because these particles go past our nasal hair into the nasal cavity causing irritation and as a reflective action this dust is thrown out through sneezing.
Que. 4 Take three test tubes. Fill ¾th of each with water. Label them A, B and C. Keep a snail in test tube A, a water plant in test tube B, and in C, and keep both the snail and plant. Which test tube would have the highest concentration of CO2?
Ans. 4 The test tube ‘A’ will have the highest concentration of CO2 because it has a snail in it. The snail will breathe in oxygen and breathe out CO2 but that’s not the case in the test tube ‘B’ and ‘C’ because they have a plant present in them which will utilize the CO2 and release oxygen via photosynthesis.
Que. 5 Tick the correct answer:
(a) In cockroaches, air enters the body through
(i) Lungs
(ii) Gills
(iii) Spiracles
(iv) Skin
(b) During heavy exercise, we get cramps in the legs due to the accumulation of
(i) Carbon dioxide
(ii) Lactic acid
(iii) Alcohol
(iv) Water
(c) The normal range of breathing rate per minute in an average adult person at rest is:
(i) 9–12
(ii) 15–18
(iii) 21–24
(iv) 30–33
(d) During exhalation, the ribs
(i) Move outwards
(ii) Move downwards
(iii) Move upwards
(iv) Do not move at all
Ans. 5 (a) (iii) Spiracles
(b) (ii) Lactic acid
(c) (ii) 15-18
(d) (ii) Moves Downward
Que. 6 Match the items in Column I with those in Column II:
| Column I | Column II |
| (a) Yeast | (i) Earthworm |
| (b) Diaphragm | (ii) Gills |
| (c) Skin | (iii) Alcohol |
| (d) Leaves | (iv) Chest Cavity |
| (e) Fish | (v) Stomata |
| (f) Frog | (vi) Lungs and Skin |
| (vii) Tracheae |
Ans. 6 The correctly matched items in Column I with those in Column II are:
| Column I | Column II |
| (a) Yeast | (iii) Alcohol |
| (b) Diaphragm | (iv) Chest Cavity |
| (c) Skin | (i) Earthworm |
| (d) Leaves | (v) Stomata |
| (e) Fish | (ii) Gills |
| (f) Frog | (vi) Lungs and Skin |
Que. 7 Mark ‘T’ if the statement is true and ‘F’ if it is false:
(i) During heavy exercise the breathing rate of a person slows down. (T/F)
(ii) Plants carry out photosynthesis only during the day and respiration only at night. (T/F)
(iii) Frogs breathe through their skins as well as their lungs. (T/F)
(iv) Fishes have lungs for respiration. (T/F)
(v) The size of the chest cavity increases during inhalation. (T/F)
Ans. 7 (i) During heavy exercise the breathing rate of a person slows down. (F), breathing rate increases*.
(ii) Plants carry out photosynthesis only during the day and respiration only at night. (F), plants carry out respiration throughout the day and night*.
(iii) Frogs breathe through their skins as well as their lungs. (T)
(iv) Fishes have lungs for respiration. (F), fishes have gills for respiration*.
(v) The size of the chest cavity increases during inhalation. (T)
Que. 8 Given below is a square of letters in which are hidden different words related to respiration in organisms. These words may be present in any direction — upwards, downwards, or along the diagonals. Find the words for your respiratory system. Clues about those words are given below the square.
(i) The air tubes of insects.
(ii) Skeletal structures surrounding the chest cavity.
(iii) Muscular floor of chest cavity.
(iv) Tiny pores on the surface of a leaf.
(v) Small openings on the sides of the body of an insect.
(vi) The respiratory organs of human beings.
(vii) The openings through which we inhale.
(viii) An anaerobic organism.
(ix) An organism with a tracheal system.
Ans. 8 (i) Trachea
(ii) Ribs
(iii) Diaphragm
(iv) Stomata
(v) Spiracles
(vi) Lungs
(vii) Nostrils
(viii) Yeast
(ix) Ant
Que. 9 The mountaineers carry oxygen with them because:
(a) At an altitude of more than 5 km there is no air.
(b) The amount of air available to a person is less than that available on the ground.
(c) The temperature of air is higher than that on the ground.
(d) The pressure of air is higher than that on the ground.
Ans. 9 (b) The amount of air available to a person is less than that available on the ground.
Credits and Refernces
- Class 7th Science NCERT Textbook
- Image by freepik
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