Wednesday, 20 April 2016


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

ANSWER: - Our body needs energy for all activities. While doing heavy exercises like running, there is larger demand of energy to perform those activities. Hence more oxygen is required to meet extra demand of energy. Therefore an athlete breathes faster.

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

ANSWER:-In both aerobic and anaerobic respiration, the food is broken down to release energy.

Aerobic respiration:-
i)It is the process of breakdown of food in the presence of oxygen.
ii)Its end products are CO2 and H2O.
iii)It takes longer time to release energy

Anaerobic respiration:-
i)It is the process of breakdown of food in the absence of oxygen
ii) End products of anaerobic respiration can be lactic acid or CO2 and alcohol.
iii)It is a fast process as compared to aerobic respiration.

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

ANSWER:-When we inhale dust-laden air, dirt particles are captured within the nostrils.
Sometimes they get past the nostril hair in the nasal cavity and irritate the lining of the cavity.
As a result we sneeze. Sneezing expels these foreign particles from the inhaled air and a dust free, clean air enters our body.

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?


Test tube A will have the highest concentration of CO2. This is because test tube A contains snail. Snail is an organism that breathes in O2 and breathes out CO2. Hence, CO2 concentration increases in test tube A.
Test tube B contains a water plant, which takes in CO2 for food synthesis and gives out O2.
Hence, more O2 concentration is found in test tube B.
Test tube C contains both a snail and a plant. The CO2 produced by the snail is utilized by the plant for its food synthesis and the O2 released by the plant is utilized by the snail for respiration. Therefore, test tube A has the highest concentration of CO2.

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

a)(iii) spiracles
b)ii. Lactic acid
c)(ii) 15-18
d)(ii) move downwards

6) Match the items in Column I with those in Column II:

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

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. (F)
(ii) Plants carry out photosynthesis only during
the day and respiration only at night. (F)
(iii) Frogs breathe through their skins as well as their lungs. (T)
(iv) The fishes have lungs for respiration. (F)
(v) The size of the chest cavity increases during inhalation. (T)