10

Q1. What is the function of the respiratory system?

Solution

The function of the respiratory system is to allow gaseous exchange (oxygen and carbon dioxide) through all parts of the body.

Q2. What is breathing?

Solution

Breathing means taking in air rich in oxygen and giving out air rich in carbon dioxide with the help of respiratory organs.

Q3. What is the site of occurence of aerobic and anaerobic respiration?

Solution

Aerobic respiration occurs in cytoplasm and mitochondria whereas anaerobic respiration occurs only in cytoplasm.

Q4. What are yeasts? How do they respire?

Solution

Yeasts are single-celled organisms. They respire anaerobically to yield alcohol. They are, therefore, used to make wine and beer.

Q5. (i) What is breathing?(ii) Differentiate between aerobic and anaerobic respiration.

Solution

(i) Breathing is the process by which air rich in oxygen is taken inside the body of an organism and air rich in carbon dioxide is expelled from the body with the help of breathing organs. (ii) Difference between aerobic and anaerobic respiration: Aerobic respiration Anaerobic respiration 1. Aerobic respiration takes place in the presence of oxygen. 2. Complete breakdown of food occurs in aerobic respiration. 3. The end products in aerobic respiration are carbon dioxide and water. 4. Aerobic respiration produces a considerable amount of energy. 1. Anaerobic respiration takes place in the absence of oxygen. 2. Partial breakdown of food occurs in anaerobic respiration. 3. The end products in anaerobic respiration may be alcohol and carbon dioxide (as in yeast), or lactic acid (as in muscles) 4. Much less energy is produced in anaerobic respiration.

Q6. Explain the terms inhalation and exhalation.

Solution

The taking in of air rich in oxygen into the body is called inhalation and giving out of air rich in carbon dioxide is known as exhalation.

Q7. Why do cells need energy?

Solution

Each cell of an organism performs certain functions such as nutrition, transport, excretion and reproduction. To perform these functions, the cell needs energy.

Q8. During breathing, what changes occur in the size of the chest cavity?

Solution

During inhalation, the ribs move outwards due to which the size of chest cavity increases. On the other hand, when we exhale, the size of chest cavity tends to decrease.

Q9. Do snails have lungs for respiration? How do they breathe?

Solution

No, snails do not possess lungs. They respire through their skin.

Q10. Transpiration nourishes the plant. Explain.

Solution

Transpiration brings about transport of minerals because the water pulled from the roots also contains certain minerals. Thus, it nourishes the plant.

Q11. Explain the mechanism of gaseous exchange during respiration.

Solution

1) In human beings, alveoli in lungs provide a surface where the exchange of gases takes place. 2) Alveoli are surrounded by blood capillaries through which O₂ diffuses from alveoli to blood and from blood CO₂ diffuses in lungs. 3) O₂ further gets transported to all the cells in the body.

Q12. How is energy released during anaerobic respiration?

Solution

In the absence of oxygen, glucose breaks down into alcohol and carbon dioxide, with the release of energy.

Q13. What is the composition of the air which we inhale and exhale?

Solution

During inhalation, we take about 21% oxygen and 0.04% carbon dioxide in our lungs. While during exhalation, 16.4% oxygen and 4.4% carbon dioxide is taken out of the lungs.

Q14. Is the breathing rate normal during rest?

Solution

During rest, the level of carbon dioxide is low, so the breathing rate is also slow. This ensures an appropriate amount of oxygen is delivered to the muscles and other organs.

Q15. How do earthworms breathe?

Solution

Earthworms breathe through their skin. The skin of an earthworm is moist and slimy and gases can easily pass through it.

Q16. How do plant roots take in oxygen?

Solution

Roots take up air from the air spaces present between the soil particles.

Q17. Give two similarities between aerobic and anaerobic respiration.

Solution

a.During both processes, energy is released by the breakdown of food. b.Carbon dioxide and water are also released during these processes.

Q18. Aquatic animals breathe in water. Explain.

Solution

Aquatic animals like fish, mussels and prawns have gills which help them breathe the dissolved oxygen in water. Gills are composed of a large number of thin filaments.

Q19. How is O₂ transported by the blood from lungs to the tissues? Make a flow chart.

Solution

Lungs → O₂ blood to → pulmonary vein → left auricle → left ventricle → body

Q20. (i) Why do frogs use their lungs as well as skin for breathing? (ii) How do plant roots take in oxygen?

Solution

(i) On land, frogs use their lungs to breathe, but there are no ribs or diaphragm to support breathing. The skin of a frog is permeable to oxygen, carbon dioxide and water. There are a number of blood vessels near the surface of the skin. So, when a frog is underwater, oxygen is transmitted through the skin directly into the bloodstream.(ii) Roots take up air from the air spaces present between the soil particles.

Q21. What is breath?

Solution

One inhalation plus one exhalation equals one breath

Q22.

State the role of stomata in plants?

How do snakes respire?

Solution

Stomata are the minute openings present on the surface of leaves. They are responsible for the gaseous exchange in plants. During daytime, carbon dioxide enters through the stomata and used up for photosynthesis. Oxygen produced is given out through stomata. At night, it is vice a versa, oxygen is taken in while carbon dioxide is given out through stomata. During transpiration, the excess amount of water is also expelled out through stomata in the form of water vapour.

Snakes respire through the normal contraction and relaxation of muscles present between the ribs. However, they lack a diaphragm.

Q23. Why do muscle cramps arise after a heavy exercise?

Solution

The cramps occur when muscle cells respire anaerobically. The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes muscle cramps.

Q24. In plants, how is respiration different from photosynthesis?

Solution

Respiration Photosynthesis 1. Food is broken down. 1. Food is manufactured. 2. Energy is released. 2. Energy is stored. 3. Oxygen is used, and carbon dioxide is a by-product. 3. Oxygen is released as a by-product, and carbon dioxide is used. 4. It is a continuous process. 4. It occurs only during the day. 5. It occurs in all cells. 5. It occurs only in cells containing chlorophyll.  

Q25. Mention any four activities due to which the breathing rate can increase.

Solution

Breathing rate can increase after brisk walking, running, climbing stairs and jumping.

Q26. Compare the breathing rate of a normal person and a sick person.

Solution

A sick person will breathe 2 - 3 times more air than a normal person, at rest.

Q27. How does smoking damage our lungs?

Solution

Smoking is a practice in which we inhale tobacco smoke. This smoke gets absorbed by the lungs and can further damage them.

Q28. Define breathing rate.

Solution

The number of times a person breathes in a minute is termed as the breathing rate. Both inhalation and exhalation takes place during one breath.

Q29. Name another gas which is also inhaled and exhaled along with carbon dioxide and oxygen.

Solution

Nitrogen is also inhaled and exhaled along with oxygen and carbon dioxide.

Q30. (i) How do plants respire?(ii) If a potted plant is over-watered for a long time, then the plant may die. Give reason.

Solution

(i) In plants, each part can independently take in oxygen from the air and give out carbon dioxide. In the cells, the oxygen is used to break down glucose into carbon dioxide and water.(ii) If a potted plant is over-watered for a long time, then the plant may die because too much water expels all the air from in-between the soil particles and water is not available for aerobic respiration.

Q31. Describe the process of internal respiration in human beings.

Solution

The process of internal respiration takes place in the mitochondria of cells. The steps of this process are as follows- i. The oxygen rich air is first transferred to the body cells by diffusion as body cells have low O₂ concentration. ii. Oxygen present in the cells is used to break down the complex molecules of food i.e. oxidation of food takes place. iii. CO₂, water and energy is released. Energy is stored in the form of ATP. iv. Similarly, due to diffusion, CO₂ flows from the cells into the blood.

Q32. (i) Why do we sneeze?(ii) During breathing, what changes occur in the size of the chest cavity?

Solution

(i) When we inhale, some unwanted particles such as dust, pollens get trapped in the hair present in our nasal cavity. However, sometimes these particles may get pass through 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.(ii) During inhalation, the ribs move outwards due to which the size of chest cavity increases. On the other hand, when we exhale, the size of chest cavity tends to decrease.

Q33. What is the average breathing rate of an adult human being at rest?

Solution

On an average, an adult human being at rest breathes in and out 15 - 18 times in a minute.

Q34. Explain the process of aerobic respiration.

Solution

When breakdown of glucose occurs with the use of oxygen, it is called aerobic respiration. In the cell, glucose is broken down into carbon dioxide and water by using oxygen.

Q35. Does the breathing rate increase during exercise? Why?

Solution

Yes, the breathing rate increases during exercise because the level of carbon dioxide in the blood becomes high. As a result, the rate of cellular respiration also increases.

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

Solution

After a physical activity, we take deep breathes and inhale more oxygen. As a result, more oxygen is supplied to our cells and the process of breakdown of food speeds up. Due to this, more energy is released and we tend to feel hungry.

Q37. What happens during inhalation with respect to chest cavity and muscles?

Solution

• The process by which air is taken into the lungs is termed as inhalation.
• During inhalation, the muscles between the ribs contract and pull the ribs upward. This results in an automatic forward movement of the chest wall thereby increasing the volume of the chest cavity.
• There is a simultaneous contraction of the diaphragm further, which increases the volume of the chest cavity further.
• This decreases the pressure within the chest cavity. At the same time, atmospheric air rushes into the lungs through the respiratory passage.

Q38. In the Lungs:

What substance is taken into the body? 

What substance is removed from the body?

Solution

O₂

CO₂

Q39. Explain the breathing mechanism in insects.

Solution

Insects have a network of air tubes called tracheae for gas exchange. Oxygen rich air rushes through spiracles (or small openings) 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. These air tubes or tracheae are found only in insects.

Q40. If a potted plant is over-watered for a long time, then the plant may die. Give reason.

Solution

If a potted plant is over-watered for a long time, then the plant may die because too much water expels all the air from in-between the soil particles and water is not available for aerobic respiration.