Respiration in Organisms

Q36. Why do we feel hungry after a physical activity?

Ans. When we need extra energy, we breathe faster. As a result more oxygen is supplied to our cells. It speeds up the breakdown of food and more energy is released. Due to rapid breakdown of food we feel hungry.

Q37. What is anaerobic respiration?

Ans. Food can also be broken down, without using oxygen. This is called anaerobic respiration. Breakdown of food releases energy.

Q38. Do the plants also respire?

Ans. Like other living organisms, plants also respire for their survival. They also take in oxygen from the air and give out carbon dioxide. In the cells oxygen is used to break down glucose into carbon dioxide and water as in other organisms.

Q39. When we release our breath after holding it for some time, we had to breathe heavily. Why it was so?

Ans.  This is so, because whenever we need extra energy, we breathe faster. As a result more oxygen is supplied to our cells. It speeds up the breakdown of food and more energy is released.

Q40. How does exchange of gases take place in insects?
Or
Explain respiration in insects.

Ans. Insects have a network of air tubes called tracheae for gas exchange.

Oxygen rich air rushes through spiracles into the tracheal tubes, diffuses into the body tissue, and reaches every cell of the body. Similarly, carbon dioxide from the cells goes into the tracheal tubes and moves out through spiracles.

Q41. When and where does anaerobic respiration occur in humans?

Ans. During heavy exercise, fast running, cycling, walking for many hours or heavy weight lifting, the demand for energy is high. But the supply of oxygen to produce the energy is limited. Then anaerobic respiration takes places in the muscle cells to fulfill the demand of energy.

Q42. What is the percentage of oxygen and carbon dioxide in inhaled and exhaled air?

Ans. When we exhale, we breathe out less oxygen but more carbon dioxide than we inhale.

Inhaled air: Oxygen 21% and Carbon dioxide 0.04%

Exhaled air: Oxygen 16.4 % and Carbon dioxide 4.4%

Q43. Why do we get relief from cramps after a hot water bath or a massage?

Ans. Hot water bath or massage improves circulation of blood. As a result, the supply of oxygen to the muscle cells increases. The increase in the supply of oxygen results in the complete breakdown of lactic acid into carbon dioxide and water. Thus, we get relief from cramps after a hot water bath or a massage.

Q44. Why do we often sneeze when we inhale a lot of dust-laden air?

Ans.  When we inhale a lot of dust-laden air, the particles get trapped in the hair present in our nasal cavity. However, sometimes these particles may get past the hair in the nasal cavity. Then they irritate the lining of the cavity, as a result of which we sneeze. Sneezing expels these foreign particles from the inhaled air and a dust free, clean air enters our body.

Q45. How does respiration occur in plants?
Or
How do the plants breathe in oxygen?

Ans. In plants each part can independently take in oxygen from the air and give out carbon dioxide. Roots take in air present in the soil. Leaves have tiny pores called stomata through which they exchange gases. The breakdown of glucose in the plant cells is similar to that in other living beings.

Q46. What parts of the human body are involved in respiration?

Ans. We take in air through our nostrils. When we inhale air, it passes through our nostrils into the nasal cavity. From the nasal cavity, the air reaches our lungs through the windpipe. Lungs are present in the chest cavity. This cavity is surrounded by ribs on the sides. A large, muscular sheet called diaphragm forms the floor of the chest cavity. Breathing involves the movement of the diaphragm and the rib cage.