IV. Answer the following questions in two sentences.

1. Describe gaseous exchange in the human body.

Ans:- Gaseous exchange is the process that constantly supplies the blood with fresh oxygen and helps in removing most of the carbon dioxide that is collected in the blood.

2. What is cellular respiration?

Ans:- The process of breaking down of food in the cells with the release of energy is called cellular respiration.

3. Differentiate between aerobic and anaerobic respiration.

Ans:- Aerobic respiration

1. It takes place in the presence of oxygen.

2. In this type of respiration the waste products are CO2 and H2O.

3. It is used by higher order living organisms like animals and plants to produce energy.

4. It produces comparatively more energy.

Anaerobic respiration:-

1. It takes place in the absence of oxygen.

2. In this type of respiration waste products are CO2 and alcohol.

3. Generally it is used by microorganisms to produce energy.

4. It produces comparatively less energy.

4. Explain respiration in birds.

Ans:- The air enters through the trachea to bird's lungs. Then it enters in the air sacs. The blood carries the oxygen from the air secs to each and every part of the body to produce energy.

5. How does gaseous exchange take place in earth worms?

Ans:- The earthworms exchange gases through their moist skin. The entire body surface is the respiratory organ.

6. What causes cramps in a person?

Ans:-  At times, while playing or running, the muscles of the person fails to receive enough oxygen. At that times the muscles respire anaerobically for a short period of time. This produces lactic acid and the person develops cramps.

V. Answer the following questions in about four to five sentences.

1. How are respiratory Systems different in different animals?

Ans:-  Respiratory systems are different in different animals. Organism like human and other animals uses their nostrils to inhale the air and lungs to gaseous exchange and finally the blood will carry the oxygen to every cells. On the other hand the insect doesn't have lungs or nostrils. They have tracheal system which is made up of spiracles and trachea to carry on their respiration system. Birds have lungs and air sacs for the process of respiration. For the process of respiration frogs uses their moist skin and lungs, fish uses their gills.

2. Differentiate between inhalation and exhalation.

Ans:- Inhalation:- 

1. Diaphragm contracts and flattens.

2. Volume of chest cavity increases.

3. Lungs expand.

4. Air flows into the lungs.

Exhalation:-

1. Diaphragm relaxes and becomes dome-shaped. 

2. Volume of chest cavity decreases.

3. Lungs contract.

4. Air is forced out of the lungs.

3.  How does the air that we breathe in reach the lungs?

Ans:- The air that we breath passes through the nostrils. The hair and mucus present in nostrils trap dust and germs present in the air. Nostrils also warm the air to match the body temperature. Then the air enters a tube like structure called trachea(windpipe). The trachea is divided into two narrow tubes called bronchi. Through bronchi the air enters the two lungs.

4. How is carbon dioxide removed from the body?

Ans:-  During respiration carbon dioxide is produced in the cells. The red blood cells carries the CO2 and reaches the heart. Then the heart sends the CO2 carrying blood to the lungs where the CO2 is detached from the red blood cells and enters the air sacs. Carbon dioxide is removed from the lungs when we breathe out.

5. Explain respiration in insects.

Ans:- The respiratory system of an insect is known as the tracheal system. It is made up of spiracles and trachea. Insect excess air through tiny holes called spiracles which are located on the body. Spiracles open into narrow tubes called trachea. The air enters through the spiracles and is supplied to every part of the body.