Matric Notes Biology Class 10th Ch 10 Gaseous Exchange Long Questions

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Q1: The gaseous exchange in plants is important for photosynthesis and respiration. Explain the types of gaseous exchange and its mechanism.

Ans: Gaseous exchange in plants:

Definition:

The exchange of oxygen and carbon dioxide between organisms and environment.

Types of gaseous exchange in plants:

1. Gaseous exchange through epidermis.

2. Gaseous exchange through stomata.

3. Gaseous exchange through lenticels.

Mechanisms of gaseous exchange in plants:

Exchange of oxygen and carbon dioxide:

During the day time all plants cells are carrying out photosynthesis. The green plants (leaves) of plants are also carrying out photosynthesis, for photosynthesis the leaves use carbon dioxide which is produced during respiration. They also take C02 from the environment, for respiration leaves use oxygen which is produced during photosynthesis.

During respiration they release C02 which is used in photosynthesis. During night all cells are carrying out respiration while there is no photosynthesis so the cells get oxygen from the environment and release C02

Gaseous exchange through epidermis:

In plants the gaseous exchange between the body and the environment occurs through the surface. The outer surface of the root, stem and leaves is called epidermis. This layer allows the exchange of gas between the inner cells and the environment. At some parts a thick cuticle is present over the epidermis; it also allows the exchange of gases.

Gaseous exchange through stomata:

In leaves and young stems, the epidermis has small pores called stomata. In these parts the air moves in and out through stomata.

Gaseous exchange through lenticels:

In woody stems, the entire surface is covered by bark, gaseous exchange cannot occur through bark. The bark contains special pores called lenticels, which allow the gaseous exchange with the environment.

Q2: Describe the mechanism of breathing in human beings?

Ans: Breathing:

Definition:

The inhalation and exhalation of air for the intake of O2 and giving out of CO2

Mechanism:

Breathing consists of two phases, the taking in of air is called inspiration and letting out of air is called expiration.

These two processes takes place continuously one after the other.

1. Inspiration

During the inspiration the volume of the chest cavity increases and the pressure in the lungs decreases. It happens due to two reasons.

i. The muscles of the diaphragm contract, so it becomes flat instead of its domed shaped.

ii. The intercostal muscles present between the ribs, contract. Due to their contraction, the ribcage expands.

2. Expiration:

During this expiration the muscles of ribs and diaphragm relax. The ribcage goes down to its original position whereas the diaphragm become dome shaped. The volume of the chest cavity decreased. It increases the pressure on the lungs to expel the air out.

Q3: Draw a diagram of the air passage in the human body and describe the role of different parts in the flow of air through it?

ANS: Human Air Passageways

i. Parts:

The air passage ways consist of Nostrils (Nose), nasal cavities, pharynx, Larynx, Trachea, Bronchi, and Bronchioles.

ii. Nostrils:

Two openings of the nose are called nostrils which lie on the ventral side of the head. They allow the air from outside into the two nasal cavities.

iii. Nasal Cavities:

The inhaled air passes through the nose into the nasal cavities. In nasal cavities the air undergoes several important changes. The air is warmed, moistened and dust freed by the cilia (hairs) and the mucus membrane.

iv. Pharynx:

The nasal cavities lead into the pharynx which is about 4.5 inches long muscular passage. It contains tonsils and adenoids which are used to trap and filter microorganisms. Tonsils and adenoids are the organs of lymphatic system.

v. Larynx

The air moves from pharynx into the larynx. Larynx surrounds the upper part of the trachea. The larynx is also known as voice or sound box. Cavity of the larynx is called glottis which is guarded by epiglottis. The epiglottis is cartilaginous flap (cover). When we inhale air the epiglottis closes the esophagus to prevent the entry of food into the larynx. It is not possible to swallow and inhale at the same time.

vi. Trachea

The larynx opens into the trachea which is also known as wind pipe. The trachea is a tubular structure which lies in the chest cavity. The inner surface of the trachea is ciliated and secretes mucus. This helps to filter, moist and warm the incoming air. The trachea has 16-20 C shaped cartilaginous rings which prevent it from collapsing and keep the passage of air open

vii. Bronchi:

Inside the thorax the trachea divides at its lower and into two branches called bronchi. Each bronchus enters the lungs of its own side. The bronchi also possess the rings but smaller than those of the trachea. Each bronchus on entering the lungs divides and sub divides progressively into smaller bronchi.

viii. Bronchioles:

When the smaller bronchi attain the diameter of one millimeter or less then they are called bronchioles. Bronchioles have no cartilage. The bronchioles are made up of circularly arranged smooth muscles.

ix. Air Sac:

The bronchioles divide deep into the lungs and finally open into a large number of air-sacs which are the functional units of lungs and resemble the bunch of grapes.

x. Alveoli:

Each air sacs consists of many microscopic structures called alveoli. The bronchi and alveoli are present within the lungs. The alveoli form the inner surface of the lungs and increase their respiratory surface. The alveoli contain a network of blood capillaries where gaseous exchange occurs.

Q4: What are the causes of respiratory disorders such as bronchitis, pneumonia and lung cancer?

Ans: Respiratory Disorders: Bronchitis:

When the lining of the bronchi or bronchioles becomes inflamed or infected, this condition is called bronchitis.

Symptoms:

Bronchitis reduces the amount of air that can flow and causes formation of mucus in the airways.

Causes:

Bronchitis is caused by viruses, bacteria and their particles that irritate the bronchial tubes.

Treatment:

▪ Short term bronchitis resolves without treatment in two weeks.

▪ If condition doesn’t improve the patient is given medicines. Antibiotics are used when bronchitis due to bacterial infection.

▪ When bronchitis is due to viral infection, antiviral medicines are used.

▪ Coughing helps to remove irritants from the bronchi.

Pneumonia

Pneumonia is an infectious disease of lungs.

Causes:

Pneumonia is caused by virus, bacteria and fungi.

Source of transmission:

Pneumonia can be transmitted by breathing in small droplets. These droplets come into the air when a pneumonia

person cough or sneezes. Pneumonia can occur when bacteria, virus that are present in the mouth and throat enter the lungs.

Severe Pneumonia:-

If a person is already attacked by another disease and have become weak, he may suffer from severe pneumonia. People who have suffered recently from viral infection, lung disease and heart diseases have more chances for pneumonia.

Symptoms:

General symptoms of pneumonia are cold, (sneezing, and sore throat)

i. High fever (about 104"F)

ii. Shivering chill.

iii. Cough with sputum.

Lung Cancer:

Lung cancer is a very dangerous and fatal respiratory disease, which results from uncontrolled cell division of the lungs. It is more common in men than in women.

Causes:

The most common causes of lung cancer are:

➢ Smoking
➢ Industrial carcinogens
➢ Air pollution.
➢ Tar of cigarette is the major cause of lung cancer

Symptoms:

The major symptoms of lung cancer are

➢ Cough with sputum.
➢ Pleural chest pain.
➢ Breathlessness