An athlete requires more energy during and after the race. Since demand for the energy is high, so oxidation of food must be speeded up. This requires more oxygen to be supplied. This is why an athlete not only breathes fast, but also takes deep breathes and thus inhale more oxygen.

Question - 2 : -
List the similarities and differences between aerobic and anaerobic respiration.

Answer - 2 : -

Similarities:

Aerobic Respiration	Anaerobic Respiration
1. It starts with the breakdown of a nutrient (glucose).	1. It also starts with the breakdown of a nutrient (glucose).
2. It yields byproducts.	2. It also yields byproducts.
3. It takes place in a cell.	3. It also takes place in a cell.
4. In this process energy is released.	4. In this process also energy is released.

Differences:

Aerobic Respiration	Anaerobic Respiration
1. It is the process of breakdown of glucose in the presence of oxygen.	1. It is the process of breakdown of glucose in the absence of oxygen.
2. Glucose is completely oxidised.	2. Glucose is incompletely oxidised.
3. The end products formed are CO₂, H₂O and energy.	3. The end products formed are C0₂, ethyl alcohol (organic acid) and energy.
4. Energy released is more. (38 ATP molecules).	4. Energy released is less (2 ATP molecules).
5. It takes place in all higher organisms.	5. It takes place in lower organisms like yeast and muscles of man.
6. The reactions take place in the cytoplasm and mitochondria.	6. The reactions take place only in the cytoplasm.

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

Answer - 3 : -

When we inhale dust particles, pollens, etc., the particles get trapped in the hair present in our nasal cavity. However, sometimes these particles may pass the hair in the nasal cavity, where they irritate the lining of the cavity, as a result of which we sneeze. Sneezing expels these foreign particles from the inhaled air and a dust- free, clean air enters our body.

Question - 4 : -
Take three test-tubes. Fill 3/4th 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?

Answer - 4 : -

The exchange of gases in three test-tubes can be shown as in Fig.

Fig. (A) In test tube A; CO₂ is produced byrespiration of snail (No consumption of CO₂).
(B) Intest tube B; CO₂ isproduced by respiration of plant and much higher amount of CO₂ is consumed duringphotosynthesis.
(C) Intest tube C; CO₂ isproduced by respiration of snail and plant and CO₂ is consumed during photosynthesis.
It is clear from the above observation that the highest concentration of CO₂ will be in test tubeA.

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

Answer - 5 : -
(a) (iii) spiracles
(b) (ii) lactic acid
(c) (ii) 15 – 18
(d) (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) Tracheae

Answer - 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 :
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)

Answer - 7 : -
F
F
T
F
T
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 air is higher than that on the ground.
(d) the pressure of air is higher than that on the ground.

Answer - 8 : -
(b) The amount of air available to a person is less than that available on the ground.

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