Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 3.2A Respiration: Organ-Level Respiration offer valuable context and analysis.
WBBSE Class 9 Science Chapter 3.2A Question Answer – Respiration: Organ-Level Respiration
Very Short Questions and Answers : (1 mark for each question)
Question 1.
Which physiological process provides energy to perform life activities?
Answer:
Respiration provides energy to perform life activities.
Question 2.
Which typical respiratory organ is seen in halophytic plants?
Answer:
Pneumatophore or breathing root is the typical respiratory organ of the halophytic plants.
Question 3.
Name two organisms, which exchange respiratory gases through body surface.
Answer:
Amoeba and Hydra exchange respiratory gases through body surface.
Question 4.
Name two invertebrates, which perform organ-level respiration by skin.
Answer:
Earthworms and leeches are two invertebrates which perform organ-level respiration by skin.
Question 5.
Name two invertebrates, which perform organ-level respiration by gills.
Answer:
Crabs and prawns perform organ-level respiration by gills.
Question 6.
Name a vertebrate, which is capable of performing organ-level respiration by skin.
Answer:
Frogs are capable of performing organ-level respiration through skin.
Question 7.
Which parts of gills act as the site of gaseous exchange?
Answer:
Gill lamellae act as the site of gaseous exchange.
Question 8.
Which part of lungs act as the site of gaseous exchange?
Answer:
Alveoli of lungs act as the site of gaseous exchange.
Question 9.
Mention a common feature of gill lamellae and alveoli of lungs.
Answer:
Both gill lamellae and alveoli of lungs are well vascularised.
Question 10.
Name two parts of the human respiratory system, which do not take part in gaseous exchange?
Answer:
Trachea and bronchioles do not take part in gaseous exchange.
Question 11.
Through which opening, air enters into the trachea from pharynx?
Answer:
Air enters into the trachea from pharynx through an opening, called glottis.
Question 12.
Where is larynx located?
Answer:
Larynx is located at the upper end of the trachea.
Question 13.
Where is bronchus located?
Answer:
Bronchus is located at the lower end of the trachea.
Question 14.
Which bony structure holds the gill lamellae in fishes?
Answer:
In fishes, the gill lamellae are held by bony gill arch.
Question 15.
Which bony plate covers the gill chamber of bony fishes?
Answer:
Operculum covers the gill chamber of bony fishes.
Question 16.
Which fine tubular structures supply air directly to the cells in the body of insects?
Answer:
Tracheoles supply air directly to the cells in the body of insects.
Question 17.
How much air does a healthy adult human inhale or exhale during normal breathing?
Answer:
A healthy adult human inhales or exhales 500 ml of air during normal breathing.
Question 18.
What is the maximum volume of air, which a healthy adult human can hold in the lungs?
Answer:
A healthy adult human can hold a maximum of 4500-5000 \mathrm{ml} of air in the lungs.
Question 19.
How can a person increase the vital capacity of the lungs?
Answer:
A person can increase the vital capacity of the lungs by performing breathing exercises or ‘pranayam’.
Question 20.
Mention two very common diseases caused due to smoking.
Answer:
Smoking causes emphysema and COPD (Chronic Obstructive Pulmonary Disease).
Question 21.
Name the flattened sheet of respiratory muscle, which separates the thoracic cavity from the abdominal cavity.
Answer:
The flattened sheet of respiratory muscle which separates the thoracic cavity from abdominal cavity, is called diaphragm.
Question 22.
Which typical structure prevents the entry of food particles into the larynx?
Answer:
A cartilaginous valve, called epiglottis, prevents entry of food particles into the larynx.
Question 23.
Which structures prevent flattening of trachea during exhalation?
Answer:
There are 16 to 20 half ring-like cartilaginous structures, fitted anteriorly to the trachea, which prevent its flattening during exhalation.
Question 24.
What is the accessory respiratory organ of Koi fish called?
Answer:
The accessory respiratory organ of Koi fish is called labyrinth organ.
Question 25.
Name two muscles of human body, which help in breathing.
Answer:
Intercostal muscles and muscular diaphragm of human body help in breathing.
Question 26.
Name the two parts of pleura.
Answer:
The outer part of pleura is called parietal pleura, and the inner part of pleura is called visceral pleura.
Question 27.
Name a respiratory pigment of vertebrates.
Answer:
A respiratory pigment of vertebrates is haemoglobin.
Question 28.
Name a respiratory pigment of invertebrates.
Answer:
A respiratory pigment of invertebrates is haemocyanin.
Question 29.
When do frogs respire through their skin?
Answer:
Frogs respire through their skin during hibernation (i.e. winter sleep).
Short Questions and Answers : (2 marks for each question)
Question 1.
What is meant by organ-level respiration?
Answer:
The physical process involving the intake of oxygen in the body and release of carbon dioxide from the body, with the help of typical respiratory organs, is known as organ-level respiration.
Question 2.
How do unicellular organisms perform organlevel respiration?
Answer:
Unicellular organisms do not possess organs, therefore they do not perform organ-level respiration, but perform gaseous exchange of O2 and CO2 by diffusion through cell membrane.
Question 3.
How do sponges and jellyfishes perform organ-level respiration without respiratory organ?
Sponges and jellyfishes do not have any respiratory organ. Their body cells perform gaseous exchange by diffusion through respective cell membranes. This is how they perform organlevel respiration.
Question 4.
How does the skin of earthworm act as a respiratory organ?
Answer:
The skin of earthworm always remain moist. Atmospheric oxygen is dissolved in the film of fluid over the skin surface. By diffusion, this gas gets mixed in the blood of the capillaries below the skin. Blood plasma of earthworm contains haemoglobin, which receives oxygen and carries it to different parts of the body. This is how the skin of earthworm acts as a respiratory organ.
Question 5.
Mention the role of spiracles and trachea in the respiration of cockroaches.
Answer:
In cockroaches, 10 pairs of spiracles are present at the two lateral sides of the body. Through these pores air enters into the trachea. Trachea forms an intricate network inside the body of cockroach, which ramifies into several branches that help in gaseous exchange.
Question 6.
When and how toads and frogs perform organ-level respiration by skin?
Answer:
Frogs and toads perform organ-level respiration by skin during hibernation. They have moist, naked glandular skin. This is well permeable to gases. The cutaneous capillaries below the skin can absorb oxygen from atmosphere by diffusion, which may fulfill their need of oxygen during hibernation.
Question 7.
How does smoking affect lungs?
Answer:
Smoke of cigarettes and bidis contains different harmful compounds. This smoke enters the human lungs and forms a sticky tar which accumulates in the walls of the alveoli. Due to continuous smoking gradually the lungs lose the ability of gaseous exchange. The harmful compounds cause several diseases like emphysema, COPD and even lung cancer.
Question 8.
How many types intercostal muscles are there? Name them.
Answer:
There are two types of intercostal musclesexternal intercostal muscles and internal intercostal muscles. These muscles are present in between 12 pairs of rib bones.
Question 9.
Distinguish between trachea of cockroach and trachea of human.
Answer:
| Features | Trachea of cockroach | Trachea of human |
| 1. Number and shape | Many, which form a network | Single and straight |
| 2. Larynx | Absent | Present |
| 3. Opening | Opens through many paired spiracles | Opens through glottis |
| 4. Termination | Terminates as fine blind tubules within tissues | Terminates into numerous tiny balloon-shaped alveoli |
Long Questions and Answers : (5 marks for each question)
Question 1.
What is inhalation and exhalation? Briefly describe the salient features of the respiratory organs of animals. 2 + 3
Answer:
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
Respiratory organs of animals have three main distinctive features, which are mentioned below.
1. Moistness: A typical respiratory organ should be moist, which helps it to trap oxygen before diffusion. Moist cell membrane of unicellular organisms and moist skin of earthworms, leeches, frogs and toads trap atmospheric oxygen very efficiently.
2. Surface area: A respiratory organ should have a large surface area because more 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 & aerial respiration respectively.
3. Vascularity: A respiratory organ should be well vascularised. This helps in better exchange of the respiratory gases. Rich distribution of blood capillaries in gills and lungs make these respiratory organs highly efficient for gaseous exchange.
Question 2.
Explain the role of different parts of plant body in gaseous exchange.
Answer:
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 exchange of O2 and CO2. These are stomata, lenticels, pneumatophores etc. Their role in gaseous exchange is mentioned below.
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 specialised bean-shaped parenchyma cells, called guard cells, which open and close. Thus, allowing 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 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.
Question 3.
How do insects perform organ-level respiration with the help of trachea?
Answer:
Tracheal respiration in insects
In insects (such as cockroach), a network of a very thin-walled tubes are spread in the body. These tubes are known as trachea. Air enters into 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 form 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.
Question 4.
Briefly describe the main respiratory organ of fishes. How do fishes perform aquatic respiration? 3 + 2
Answer:
Structure of respiratory organ of fishes
Gills perform the respiratory function in fishes. In 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 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 dense network of blood capillaries.
Mechanism of aquatic respiration in fishes
Fishes continuously open and close their mouth. When they open their mouth, fresh water flows into the buccal cavity. They open the opercula to allow water to pass through 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 human lung.
Answer:
Structure of human lung
Lungs are paired, sac-like structures located in the thoracic cavity of 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 parietal and the inner one is called visceral pleura. A fluid-filled space is present in 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. Wall of each alveolus is rich in blood capillaries. That is why healthy lungs appear reddish pink.
Question 6.
Describe the breathing mechanism of man.
Answer:
Mechanism of human breathing
The organ-level respiration or breathing in man involves two phases-
1. Inspiration
2. Expiration. The mechanism of breathing is discussed below.
1. Inspiration: The events which occur during inspiration are as follows-
As we breathe in, diaphragm muscles contract and move down towards the abdominal cavity.
Intercostal (present in between ribs) muscles contract to pull the ribs upward to some extent.
By these two actions, the space inside the ribcage increases. This reduces the pressure inside the chest cavity and in the pleural fluid.
In this situation, thoracic pressure reaches below the atmospheric pressure. As a result, oxygen-rich air from the atmosphere rushes into the body through nostrils, nasal passage, glottis, larynx, trachea, bronchus and bronchioles to reach the alveoli. Gaseous exchange occurs in between alveolar air and capillary blood. After this exchange, the air inside lungs become rich in carbon-dioxide (CO2). After this, the brain sends signal for expiration.
2. Expiration: The events which occur during expiration are as follows-
- The diaphragm expands and moves towards the chest cavity.
- Intercostal muscles relax and the ribs go downward to their normal position.
- 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.
- 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? 3 + 2
Answer:
Reason of weak and diseased lungs
Lungs are very important organs in our body, which are involved in respiration. If lungs do not perform their function perfectly, we will fall sick. Lungs lose its efficienc due to aging, obesity, infections and in most cases due to smoking. A dark coloured tar is deposited in the lungs of smokers, that 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 lungs decline 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 effect, 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.
Methods of keeping the lungs fit
Breathing exercise or ‘pranayam’ keeps our lungs healthy. The basis of this exercise is steady, forceful & rhythmic inspiration & 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 keeps our lungs healthy.
