Q.1. Why does an athlete breathe faster and deeper than usual after finishing the race?

Q.2. List the similarities and differences between aerobic and anaerobic respiration.

Q.3. Why do we often sneeze when we inhale a lot of dust-laden air?

Q.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 snail and plant both. Which test tube would have the highest concentration of CO2?

Q.5.Tick the correct answer:

(a) In cockroaches, air enters the body through

• lungs
• gills
• spiracles
• skin

(b) During heavy exercise, we get cramps in the legs due to the accumulation of

• carbon dioxide
• lactic acid
• alcohol
• water

( c ) Normal range of breathing rate per minute in an average adult person at rest is:

• 9–12
• 15–18
• 21–24
• 30–33

(d) During exhalation, the ribs

• move outwards
• move downwards
• move upwards
• do not move at all

Q.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

Q.7. Mark ‘T’ if the statement is true and ‘F’ if it is false:

• During heavy exercise, the breathing rate of a person slows down. (T/F)
• Plants carry out photosynthesis only during the day and respiration only at night. (T/F)
• Frogs breathe through their skins as well as their lungs. (T/F)
• The fishes have lungs for respiration. (T/F)
• The size of the chest cavity increases during inhalation. (T/F)

Q. 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.

Q. 9. The mountaineers carry oxygen with them because:

• At an altitude of more than 5 km, there is no air
• The amount of air available to a person is less than that available on the ground.
• The temperature of the air is higher than that of the ground.
• The pressure of air is higher than that on the ground.