WBBSE Class 9 Life Science Chapter 3 Physiological Processes Of Life Respiration Long Answer Questions

Chapter 3 Physiological Processes Of Life Respiration Long Answer Type Questions

Question 1 What are inhalation and exhalation? Briefly describe the salient features of the respiratory organs of animals.


Inhalation: The mechanical process, by which organisms take in air from the environment, is called inhalation.

Exhalation: The mechanical process, by which living organisms give out carbon dioxide-rich air from their respiratory organs, into the environment, is called exhalation.

Salient features of the respiratory organs of animals:

1 Moistness: The moist cell membrane of unicellular organisms and the moist skin of earthworms, leeches, frogs, and toads act as respiratory organs. Atmospheric oxygen enters into the blood vessels through these moist skin, by diffusion.

2 Surface area: A respiratory organ should have a large surface area because surface area improves its efficiency by transporting or exchanging enough oxygen. The thin and numerous lamellae of gills and densely packed alveoli of lungs make these two organs best suited for aquatic and aerial respiration respectively.

Read and Learn More Class 9 Life Science Long Answer Questions

3 Vascularity: A respiratory organ should be well vascularised. This helps in the better exchange of respiratory gases. The rich distribution of blood capillaries in the gills and lungs makes these respiratory organs highly efficient for gaseous exchange.

WBBSE Class 9 Life Science Chapter 3 Physiological Processes Of Life Respiration Long Answer Questions

Question 2 Explain the role of different parts of the plant body in gaseous exchange.


Role of different parts of plant body in gaseous exchange:

Plants do not have typical respiratory organs like animals. Few sites on a plant body help in the exchange of O2 and CO2. These are stomata, lenticels, pneumatophores, etc.

1 Stomata: Stomata are the tiny pores, present on the surface of leaves, tender stems, and other parts of the plant body that help in the exchange of gases. These are the special intracellular spaces bordered by two specialized bean-shaped parenchyma cells, called guard cells, which open and close. Thus, allowing the exchange of gases.

2 Lenticels: Lenticels are lens-shaped spaces, formed in the cracks on the bark of trees. These function as pores, providing the pathway for the direct exchange of gases between the internal tissues and atmosphere through the bark, which is otherwise impermeable to gases.

3 Pneumatophores: Halophytes (mainly mangrove trees) grow on saline muddy soil in the delta region of rivers. This soil has poor oxygen content. To counter it, some roots of these plants grow vertically upward against gravity and come above the soil.

These roots are highly porous. These are called pneumatophores or breathing roots, which help in the exchange of gases directly from the air.

WBBSE Solutions For Class 9 Life Science And Environment Chapter 3 Physiological Processes Of Life Respiration different parts of plant body involved in gaseous exchange

WBBSE Life Science And Environment Class 9 Solutions

Question 3 How do insects perform organ-level respiration with the help of the trachea?


Tracheal respiration in insects:

In insects (such as cockroaches), a network of very thin-walled tubes is spread in the body. These tubes are known as trachea. Air enters the tracheal system through tiny paired pores present on pleurites along the two sides of the body.

These pores are called spiracles. Trachea ramifies or forms branches inside the body cavity, longitudinally and transversely to form a tracheal network. The finest ends of tracheal branches are called tracheoles.

Each tracheole ends in a large tracheal end cell, which gives off some fine cytoplasmic processes. These processes enter into intercellular tissue fluid.

Gaseous exchange occurs between the tracheal end cells and tissue fluid and finally from tissue fluid to the cells by the process of diffusion.

WBBSE Solutions For Class 9 Life Science And Environment Chapter 3 Physiological Processes Of Life Respiration trachea of insect

Question 4 Briefly describe the main respiratory organ of fishes. How do fishes perform aquatic respiration?


Structure of respiratory organs of fishes:

Gills perform the respiratory function in fish. In the case of cartilaginous fishes, these are present in gill clefts, and in bony fishes, these are held in gill chambers at two sides of the head, covered with a bony plate, called the operculum. A gill has a curved bony skeletal structure, called a gill arch.

Two rows of thin and flat gill filaments are densely arranged in a parallel manner along the gill arch like teeth of a comb. Numerous, very thin membranous folds emerge from either side of a gill filament, called gill lamellae. Gill filaments and lamellae are supplied with a dense network of blood capillaries.

WBBSE Solutions For Class 9 Life Science And Environment Chapter 3 Physiological Processes Of Life Respiration through fills

Mechanism of aquatic respiration in fishes:

Fishes continuously open and close their mouth. When they open their mouth, freshwater flows into the buccal cavity. They open the opercula to allow water to pass through the gills to flood the gill filaments before leaving the two gill chambers.

As the water passes through the gills, O2 diffuses into the blood capillaries and CO2 diffuses out in the water. This is how fishes perform aquatic respiration.

Question 5 Describe the structure of the human lung. Mention its function. Structure of the human lung


Lungs are paired, sac-like structures located in the thoracic cavity of the human body, well protected by the rib cage. Lungs remain separated from the abdominal cavity by a muscular sheet or membrane, called the diaphragm.

Each lung is covered with a double-layered covering called pleura. The outer layer is called the parietal and the inner one is called the visceral pleura. A fluid-filled space is present between these two layers.

The left lung is slightly smaller with two lobes to accommodate the heart and the right one is larger with three lobes. A long, thin-walled, tubular wind-pipe or trachea goes down vertically along the medial chest line and divides into two bronchi (singular-bronchus) before entering the lungs.

Each bronchus then ramifies several times, from finer to finest air tubules, called bronchioles. Finally, each of the bronchioles ends into a tiny balloon-shaped alveolus (plural- alveoli). Thus, countless alveoli form a lung.

Two human lungs are composed of 30 to 50 crore of alveoli. The wall of each alveolus is rich in blood capillaries. That is why healthy lungs appear reddish pink.

WBBSE Solutions For Class 9 Life Science And Environment Chapter 3 Physiological Processes Of Life Respiration human lungs


1. Lungs are the chief respiratory organs in man. It helps in respiration.
2. In the lungs O2 enters from the alveolar air into the blood capillaries and CO2 comes out from the blood capillaries into the alveolar air.

WBBSE Life Science And Environment Class 9 Solutions

Question 6 Describe the breathing mechanism of man.


Mechanism of human breathing:

The organ-level respiration or breathing in man involves two phases:

1. Inspiration
2. Expiration.

1 Inspiration:

1. As we breathe in, diaphragm muscles contract and move down toward the abdominal cavity.
2. Intercostal (present in between ribs) muscles contract to pull the ribs upward to some Diaphragm comes down extent.
3. By these two actions, the space inside the ribcage increases. This reduces the pressure inside the chest cavity and in the pleural fluid.

WBBSE Solutions For Class 9 Life Science And Environment Chapter 3 Physiological Processes Of Life Respiration mechanism of human respiration inspiration and expiration

4. In this situation, thoracic pressure reaches below atmospheric pressure. As a result, oxygen-rich air from the atmosphere rushes into the body through the nostrils, nasal passage, glottis, larynx, trachea, bronchus, and bronchioles to reach the alveoli.
Gaseous exchange occurs between alveolar air and capillary blood. After this exchange, the air inside the lungs becomes rich in carbon dioxide (CO2). After this, the brain sends a signal for expiration.

2 Expiration:

1. The diaphragm expands and moves towards the chest cavity.
2. Intercostal muscles relax and the ribs go down to their normal position.
3. Due to the above two actions, the internal volume of the chest cavity reduces. As a result, pressure increases in the pleural fluid, as well as in the lungs.
4. The lungs contract and the CO2-rich air, inside the lung, is pushed out along the reverse path.

Question 7 How do the lungs get weak and diseased? How can the lungs be kept fit?


Reason for weak and diseased lungs:

Lungs are very important organs in our body, which are involved in respiration. If the lungs do not perform their function perfectly, we will fall sick. Lungs lose their efficiency due to aging, obesity, infections, and in most cases smoking.

A dark-colored tar is deposited in the lungs of smokers, which contains several potential carcinogens (cancer-inducing substances), leading to lung cancer. Smokers develop a chronic lung disease, called emphysema. In this case, gaseous exchange reduces and the efficiency of the lungs declines permanently.

Passive smokers (who unconsciously inhale the smoke released by active smokers) are the worst victims of this bad habit and also suffer from the same diseases. Due to allergic effects, a person may suffer from asthma and COPD (Chronic Obstructive Pulmonary Disease).

Infection with Mycobacterium tuberculosis may lead to a serious lung disease, called tuberculosis, whose symptoms are coughing (sometimes with sputum with blood), chest pain, weakness, weight loss, fever, etc

WBBSE Solutions For Class 9 Life Science And Environment Chapter 3 Physiological Processes Of Life Respiration cigarettes

Methods of keeping the lungs fit:

Breathing exercise or ‘pranayam’ keeps our lungs healthy. The basis of this exercise is steady, forceful, and rhythmic inspiration and expiration. It increases the extensibility of the lungs and thus, increases the oxygen intake capacity of the body.

But, pranayam should be practiced under the proper guidance of a competent yoga teacher. Moreover, swimming, cycling, jogging and even walking keep our lungs healthy.

WBBSE Solutions For Class 9 Life Science And Environment Chapter 3 Physiological Processes Of Life Respiration yoga

WBBSE Life Science And Environment Class 9 Solutions

Question 8. Write about the accessory respiratory organs with examples. Mention its necessity in animals. 3+2


Accessory respiratory organs:

In some bony fishes, living in muddy water where oxygen supply is scanty, respiration by gills is supplemented by a special organ called the accessory breathing organ. e.g. Koi (Anabas), Magur (Clarias), Singhi (Heteropneustes).

The name of the accessory respiratory organ of Magur is called the arborescent organ; for Singhi it’s a tubular air sac and for Koi, it’s a labyrinthine organ.

Necessity in animals:

1. These fishes are unable to live submerged in water and are allowed to grasp air through mouth by lifting their head above water when oxygen concentration is very low in the water. Absorption of oxygen appears to be the primary function of the accessory respiratory organ.
2. Some fishes have the natural instinct to make short excursions to the land from their primal aquatic homes.

Question 9 What is meant by active and passive smoking? Write the poisonous effect of smoking.


Active smoking: Active smoking is the intentional inhalation of tobacco smoke by a smoker. Smokers puff directly from cigarettes.

Passive smoking: Passive smoking is the involuntary inhalation of smoke from tobacco products. Such smoke is called Secondhand Smoke (SHS) or Environmental Tobacco Smoke (ETS).

The poisonous effect of smoking:

1. Emphysema means excess air in the lungs, caused by many years of smoking, resulting in chronic infection, obstruction of airways makes expiration difficult, bronchiolar obstruction increases, etc.,
2. Lung cancer or carcinoma occurs due to many carcinogenic agents present in tobacco smoke,
3. Chronic obstructive pulmonary disease (COPD)
4. Heart disease, stroke
5. Eye diseases
6. Increases the risk of tuberculosis,
7. Problems of the immune system including rheumatoid arthritis.

Leave a Comment