Question 1. Why does an athlete breathe faster and deeper than usual after finishing the race?
Solution 1. They breathe faster and deeper than usual after finishing the race because they need a lot of oxygen to release the energy they need during race.
Question 2. List the similarities and differences between aerobic and anaerobic respiration.
Solution 2. Similarities:
- Energy is released during both kinds of respiration.
- Both kind of respiration occurs inside the cells
- by-products are supplied by both.
Differences:
| Aerobic respiration | Anaerobic respiration |
| Aerobic respiration takes place in the presence of Oxygen. | Anaerobic respiration takes place in the absence of Oxygen. |
| The end products of aerobic respiration are CO2 and H2O. | The end products of anaerobic respiration are CO2 and alcohol. |
| Produces a large amount of energy as compared to anaerobic respiration. | Produces less amount of energy as compared to aerobic respiration. |
| It occurs in most plant and animal cells. | It occurs in yeast and some bacteria. |
| Aerobic respiration is a slow process. | Anaerobic respiration is a fast process. |
Question 3. Why do we often sneeze when we inhale a lot of dust-laden air?
Solution 3. We often sneeze when we inhale dust-laden air because the dust irritates the nose and as a reflexive action, we sneeze to throw out dust.
Question 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, keep the snail and plant both. Which test tube would have the highest concentration of CO2?
Solution 4. In test tube A the concentration of CO2 will be higher because a snail which is an animal will exhale CO2 this will increase the concentration of CO2 but in the other two test tubes B and C there is a plant so this will decrease the concentration of CO2 as it inhales CO2.
Question 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) 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
Solution 6. a) In cockroaches, air enters the body through
Ans. (iii) spiracles
b) During heavy exercise, we get cramps in the legs due to the accumulation of
Ans. (ii) lactic acid
c) Normal range of breathing rate per minute in an average adult person at rest is:
Ans. (ii) 15–18
d) During exhalation, the ribs
Ans. (ii) move downwards
Question 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) Trachae |
Solution 6.
| 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 |
Question 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)
Solution 7.
i) During heavy exercise the breathing rate of a person slows down. False
ii) Plants carry out photosynthesis only during the day and respiration only at night. False
iii) Frogs breathe through their skins as well as their lungs. True
iv) fishes have lungs for respiration. False
v) The size of the chest cavity increases during inhalation. True
Question 8. 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 the air is higher than that on the ground.
(d) The pressure of air is higher than that on the ground.
Solution 8. (b). The amount of air available to a person is less than that available on the ground.