Answer. See Page No. 2 , Punjab Text Book 

Cellular Respiration:  Cellular respiration is the process in which the C-H bonds in food are broken by oxidation-reduction reactions and the energy is transformed into ATP.

Aerobic Respiration: In aerobic respiration, oxygen is used and there is complete oxidation of the food material. Carbon dioxide and water are also produced in this process.

Gaseous Exchange: Organisms get the oxygen, needed for cellular respiration, from their environment and provide it to their cells. The carbon dioxide produced during cellular respiration is taken out of the cells and ultimately from the body. Taking in oxygen and giving out of carbon dioxide is termed as gaseous exchange.

Breathing: The term breathing is used for the process through which animals take air in their bodies to get oxygen from it and then give out the air for getting rid of carbon dioxide.

 NOTE:  Breathing and respiration are not synonymous. Respiration involves the mechanical and the bio-chemical processes whereas breathing is only the mechanical or physical process of exchange of gases.

Answer. See Page No. 2 , Punjab Text Book 

• ••The leaves and young stems have stomata in their epidermis. The gaseous exchange occurs through these stomata.
• ••The inner cells of leaves (mesophyll) and stems also have air spaces among them, which help in the exchange of gases.
• ••In young stems and leaves, some gaseous exchange also occurs through the cuticle which ispresent over their epidermis.

Answer. See Page No. 3 , Punjab Text Book 

Leaf cells face two situations:

• ••During the daytime when the mesophyll cells of leaves are carrying out photosynthesis and respiration side by side, the oxygen produced in photosynthesis is utilized in cellular respiration. Similarly the carbon dioxide produced during cellular respiration is utilized in photosynthesis.
• ••However, during night when there is no photosynthesis occurring, the leaf cells get oxygen from the environment and release carbon dioxide through stomata.

Answer. See Page No. 3 , Punjab Text Book 

• Define : In woody stems and mature roots, the entire surface is covered by bark which is impervious to gases or water. However, there are certain pores in the layer of bark. These are called the lenticels.
• Function : The lenticels allow air to pass through them.
  
  

Answer. See Page No. 3 , Punjab Text Book 

Answer. See Page No. 5 , Punjab Text Book 

• Define: The nose encloses the nasal cavity. It opens to the outside through the openings called the nostrils. The nasal cavity is divided into two portions by a wall.
• Importance: Each portion is lined by fine hairs and mucous which filter the dust particles from the air. The mucous also moistens and warms the incoming air and keeps its temperature nearly equal to that of the body.

Answer. See Page No. 5 , Punjab Text Book 

• Glottis:  The air goes from the pharynx into the larynx. Glottis is a narrow opening at the floor of pharynx which leads into larynx.
• Epiglottis: The glottis is guarded by a flap of tissue called the epiglottis.

Answer. See Page No. 5 & 6 , Punjab Text Book 

• Pharynx:  Pharynx is a muscular passage and is common to both food and air. It extends to the opening of the oesophagus and the larynx. The air goes from the pharynx into the larynx.
• Larynx:  The larynx is a box, made of cartilage. It is present between pharynx and trachea. It is
  also called the voice box.

Answer. See Page No. 6 , Punjab Text Book 

Larynx is also called the voice box. Two pairs of fibrous bands called vocal cords are stretched across the larynx. The vocal cords vibrate when the air passes through them. This vibration produces sounds.

Answer. See Page No. 6 , Punjab Text Book 

Larynx continues to the trachea, which is also called the windpipe. It is about 12 cm long tube which lies in front of the oesophagus. There are C-shaped cartilagenous rings in the wall of trachea. The cartilages keep the trachea from collapsing even when there is no air in it.

Answer. See Page No. 6 , Punjab Text Book 

• Bronchi:  On entering the chest cavity, the trachea divides into two smaller tubes called bronchi (Singular: bronchus). The bronchi also have cartilagenous plates in their walls.
• Bronchioles: The bronchi continue dividing in the lungs until they make several fine tubes called bronchioles. The bronchioles progressively lose the cartilages as they become narrower.
• Alveolar ducts: The bronchioles progressively lose the cartilages as they become narrower. The bronchioles end as fine tubules called the alveolar ducts.
• Alveoli: Each alveolar duct opens into a cluster of pouches called alveoli. The alveoli form the respiratory surface in human body.
• Alveolus: Each alveolus is a sac-like structure lined by a single layer of epithelial cells. It is bound on the outside by a network of capillaries.

Answer. See Page No. 6 , Punjab Text Book 

• Intercoastal muscles: The chest wall is made up of 12 pairs of ribs and the rib muscles called intercoastal muscles. 
• Diaphragm:  A thick muscular structure, called diaphragm, is present below the lungs.

Answer. See Page No. 2 , Punjab Text Book

Answer. See Page No. 6 , Punjab Text Book 

Answer. See Page No. 7 , Punjab Text Book 

Answer. See Page No. 7 , Punjab Text Book

Answer. See Page No. 11 , Punjab Text Book 

Answer. See Page No. 12 , Punjab Text Book

Answer. See Page No. 12 , Punjab Text Book

Answer. See Page No. 12 , Punjab Text Book

Answer. See Page No. 13 , Punjab Text Book

Answer. See Page No. 13 , Punjab Text Book

Answer. See Page No. 14 , Punjab Text Book

Answer. See Page No. 14 , Punjab Text Book

Answer. See Page No. 14 , Punjab Text Book

Answer. See Page No. 15 , Punjab Text Book

Answer. See Page No. 14 , Punjab Text Book