Page 85 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

(f) The gaseous exchange takes place in a tiny sac-like structure present in the lungs called

alveolus (plural-alveoli).
(g) The bronchi inside the lungs divide & subdivide into bronchioles, each terminating into

an alveolus. Millions of alveoli are present in each lung.
(h) Alveoli are surrounded by blood capillaries through which oxygen is picked up and
carbon dioxide is released.

v Lungs are located in the chest cavity that is enclosed by the ribcage.
v A large muscular membrane, called the diaphragm is present at the bottom of the chest

cavity. It separates the chest cavity from the abdominal cavity.
v During inhalation, the rib cage moves up and outwords whereas the diaphragm moves

downwards. This increases the space in the chest cavity and air moves into our lungs.
v During exhalation, the rib cage contracts whereas the diaphragm moves upwards, reducing

the size of the chest cavity. This makes the air expel from the lungs.
v Cockroaches respire through tiny holes called spiracles and air tubes called tracheae that
allow the exchange of gases within their body.

v Earthworms have a soft, slimy and moist skin that helps them respire.
v Frogs have a slippery & moist skin that helps them in breathing. They have lungs too. In

water, they breath through their skin and through their lungs when on land.
v Fish breathe with the help of gills located on either side of their head, which are made up of

a numbers of comb like structures called gill filaments. These provide a large surface area
for gaseous exchange. Gill filaments are made of blood capillaries that help in absorbing the

oxygen dissolved in the water & move it into the blood. Simultaneously, the carbon dioxide
in the blood passes out through the gills into the water.
v During respiration in plants, exchange of gases takes place through the stomata, which

are tiny pores on the leaves. In stems, the exchange of gases take place through minute
permanent openings called lenticels.

v Plants respire throughout the day and also at night. At night, carbon dioxide is released into
the atmosphere through stomata. So, it is advised not to sleep under a tree at night as one
may inhale carbon dioxide.

v Respiration in leaves, stems & roots takes place through the stomata, lenticels and from the
air spaces present between the soil respectively, by the process of diffusion.

v If overwatered, the air spaces between the soil particles get clogged, due to which the roots
are not able to get enough air to respire and they can die due to lack of oxygen.

v An Indian scientfist, Dr JC Bose proposed that plants fell pain & understand affection, just as
much as humans do. He was a Nobel laureate who invented crescograph, a device that help

record the slightest movement of plant. All his experiments & researches paved the way for
better understanding of cultivation of crops.

85