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
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
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
(a) Yeast                                  (iii) Alcohol
(b) Diaphragm.                        (iv) Chest cavity
(c) Skin                                    (i) Earthworm
(d) Leaves.                              (v)
(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.
(iv) The fishes have lungs for respiration. (F)
(v) The size of the chest cavity increases during inhalation. (T)