Whenever we feel drowsy or sleepy, we start yawning. Does
yawning help us in anyway?
On a very cold morning, Boojho and Paheli were talking with
each other as they walked down to their school. They observed
that the air coming out of their mouth looked like smoke. They
were amused and wondered how it happened. Help them find
the answer
On an average, an adult human being at rest breathes 15–18
times per minute. The breathing rate, however, may differ under
different conditions. Arrange the following activities given in
the box in order of increasing breathing rates and give reason
for your answer.
sleeping, cycling, brisk walk, watching T.V
Which gas present in air is essential for aerobic respiration?
What is the role of oxygen during respiration?
Pick the odd-one-out from each of the groups given below on
the basis of respiratory organs. Give reason for your answer.
(a) cockroach, grasshopper, snail, ant
(b) lizard, cow, earthworm, snake
(c) crocodile, whale, dolphin, fish
(d) snake, tadpole, crow, goat
Fill in the blanks with suitable words.
(a) The roots of a plant take up oxygen from the ______
trapped between the ________ particles.
(b) Diaphragm forms the ___________ of the chest cavity.
(c) Exchange of gases in the leaves take place with the help
of __________.
(d) Cockroaches breathe with the help of air tubes called
___________.
Mark the following statements as True or False. Correct the false statements.
(a) Oxygen breaks down glucose outside the cells of organisms.
(b) Frogs can breathe through their skin as well as lungs.
(c) Insects have spiracles on the lower surface of the body.
(d) Exhaled air has more percentage of CO2 than inhaled air.
Earthworms and frogs breathe through their skin because of
which the skin of both the organisms is
(a) moist and rough.
(b) dry and rough.
(c) dry and slimy.
(d) moist and slimy
Fish breathe with the help of gills which are richly supplied
with blood vessels. The gills help the fish to
(a) take in oxygen from air.
(b) take in oxygen dissolved in water.
(c) absorb nutrients present in water.
(d) release waste substances in water.
Breathing is a process that
(i) provides O2 to the body.
(ii) breaks down food to release energy.
(iii) helps the body to get rid of CO2.
(iv) produces water in the cells.
Which of the following gives the correct combination of
functions of breathing?
(a) (i) and (ii) (b) (ii) and (iii)
(c) (i) and (iii) (d) (ii) and (iv)
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