Spiracles In cockroaches, air for respiration enters through small tubes/holes present on then body called spiracles.

Stomata are the tiny pores that are present on the surface of plant through which gaseous exchange occurs.

Frogs respire through their moist skin as well as through a pair of lungs

When we exhale into lime water its colour changes, into slightly milky white because exhaled air contains CO₂,

During the process of inhalation diaphragm contracts and moves downwards.

The farmers sometimes loosen the soil. This helps the root to respire through the air present in the space between soil particles.

(a) When sneezing, you should cover your nose so that the particles expelled by you would not be inhaled by others.
(b) Yes.
(c) No, it is process to remove/clear the particles harmful for us resulting in clean, fresh air to enter the lungs.
(d) Cleanliness and hygiene maintenance.

Animal A can live on land as well as in water and can respire through lungs as well as moist skin. The animal is frog.
Animal B lives in water and respires through a specific organ called gills. These are found in the tadpoles besides fishes.
The animal B is a fish. Animal C is also an aquatic animal which lives in sea water and respires through nostrils and lungs not by the gills. The animal is whale.

When we work hard or perform physical activity (like running, swimming, cycling), we need more energy. To fulfil the energy requirement, we breathe faster. Fast breathing helps in supply of more oxygen to our cells. Due to this, rate of breakdown of food increases and more energy is released. The rapid breakdown of food makes us to feel more hungry.

Frog breathe by their moist skin and through lungs also. So, they do not have any, respiratory issue.
When frog enters into water, the skin of frog helps in respiration.
The oxygen rich air enters through the skin. When the frog is on land, a pair of lungs helps in respiration.
The lungs take the oxygen-rich air through the nostrils from where the oxygen is absorbed by the blood and carried throughout the body. The carbon dioxide from the blood is diffused back through the skin and lungs into the atmosphere.

Pores present on the sides of insects are called spiracles while pores present on the surface of leaves are called stomata. These structures are responsible for the exchange of gases with the atmosphere. Differences between these two are as follows
(i) Spiracles are fewer in number as compared to stomata.
(ii) Spiracles lead to an extensive network of tracheal system which is absent in the leaves

(a) Exhalation process of respiration is being tested in the activity.
(b) The lime water in test tube B turns milky but water in test tube A remains unchanqed Because CO₂ is present in the exhaled air, it mixes with lime water in test tube B and turns it milky.

(a) Paheli had cramps in her leg muscles after running. She felt pain in her legs because of accumulation of lactic acid in the leg muscles. Lactic acid is formed due to anaerobic respiration in the muscle cells after heavy exercise or running. After heavy exercise, we require large amount of energy.
To produce more energy to meet the oxygen requirement of muscles, muscle cells perform anaerobic respiration for a short duration. Lactic acid is formed due to partial breakup of glucose. It gets accumulated in the muscle cells and causes pain and muscle cramps.
(b) The massage or hot water bath gives the relief from muscle cramp or pain, because it improves the circulation of blood leading to increase supply of oxygen to the muscle cells . It helps in complete breakdown of lactic acid into carbon dioxide and water