Biology For Class X - Chapter No. 1 - Gaseous Exchange - Long Question Answers

 

Biology For Class X - Chapter No. 1 - Gaseous Exchange - Long Question Answers

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CHAPTER 1: GASEOUS EXCHANGE
C. EXTENSIVE RESPONSE QUESTIONS:

i) What measures would you take to avoid respiratory disorders?
Ans: In order to avoid respiratory disorders the following measures should be taken.

1. Avoid smoking and passive smoking.
2. Be mindful of your environment's air quality. Test for pollutants or contaminants.
3. Prevent common colds and respiratory illnesses by washing hands frequently with soap and water.
4. Avoid large crowds during the flu season, or when some other respiratory illness is going around.
5. Stay home if sick to avoid spreading colds and respiratory illnesses to others.
6. Get regular cardiovascular exercise to boost lung fitness and overall health.
7. Practice deep breathing, or diaphragmatic breathing, exercises.
8. Take care of dental health and oral hygiene to prevent harmful bacteria from travelling from mouth to upper airway.

ii) Discuss human respiratory system with the help of suitable illustrations.
Ans: Human Respiratory System:
In humans, there is very efficient respiratory system. It consists of certain organs which are called respiratory organs. These include:

• Nose
• Pharynx
• Larynx
• Trachea
• Bronchi
• Bronchioles
• Alveoli
• Lungs

Nose:
Air from outside enters into the nasal sacs through external nostrils. This entire passage through which air passes is lined by mucous secreting ciliated cells. The internal surface has rich blood capillaries which turn the incoming air slightly hot. The hairs in nasal sacs as well as ciliated epithelial lining and mucous keep the air clean by trapping and removing dust and germs. This ensures clean air to approach the respiratory surface. In this way air is purified and is then pushed into the pharynx.

Pharynx:
The nasal cavity opens into the pharynx (throat) through two small apertures which are called internal nostrils. The pharynx is muscular passage which extend from behind the nasal cavities to the opening of oesophagus and larynx. The air goes from the pharynx into the larynx.

Larynx:
The upper most part of the wind pipe (trachea) is called the larynx. The larynx is a cartilaginous box with two fibrous bands called the vocal cords. These vibrate to produce sound. Larynx is, also called sound box or voice box. The air enters the larynx through a small aperture called glottis which is guarded by a muscular flap called epiglottis which fits into this opening while the food is being swallowed into the oesophagus. It prevents the food from entering into the trachea and choking it. During breathing epiglottis keeps the glottis open so that air goes to trachea.

Trachea:
The air tube (wind pipe) is known as trachea. It is about 12 cm long and lies in front of the esophagus. It has incomplete C shaped cartilagenous rings which are regularly placed in its wall and all along its length. These rings prevent the collapsing of the tube and thus keep the air passage wide open all the time. Trachea is also lined with ciliated mucous epithelium. Any foreign particles present in the inhaling air get trapped in the mucous that is moved out of the trachea by breathing of the cilia in the upward direction. In trachea air is further cleansed and filtered and then moved towards the lungs.

Bronchi:
The trachea in the center of the thorax while passing the chest cavity bifurcates (divides) into two smaller tubes (ducts) which are called bronchi (single bronchus). Bronchi are similar in structure to the trachea but are smaller in diameter and they have in their walls small irregular catilageuous plates. Each bronchus enters into the lungs of its own side. The right bronchus divides into three secondary bronchi and the left bronchus divides into two secondary bronchi which serve the 3 right and 2 left lobes of the lungs respectively.

Bronchioles:
The secondary bronchi further divide into very fine and thin branches (tubes) until they end in thousands of passage ways called respiratory bronchioles. The bronchioles have not cartilaginous plates in their walls. They have smooth muscle and elastic fibers. Each bronchiole opens into air sacs or alveoli.

Alveoli:
The walls of the respiratory bronchioles have clusters of tiny branches (like bunches of grapes) that along with the respiratory bronchioles are the sites of gaseous exchange, these pouches or air sacs are called alveoli (singular: alveolus). The alveoli are enormous in number. Each lung has about three hundred million alveoli.
Pulmonary artery brings deoxygenated blood from the heart into the lung. Here, it divides and re-divides until it forms a network of fine capillaries over the wall of each alveolus. Each alveolus is the respiratory surface. It's a pouch like microscopic structure made up of only one layer of cells. The walls of alveoli are very thin (1/1000 mm thick) and moist. Thus, alveoli are efficient site for gaseous exchange.

The Lungs:
There is a pair of lungs present in the chest in man. Actually, the masses of alveoli constitute lungs and their lobes. The lungs are protected by the chest box from sides and by a dome shaped muscular diaphragm from below. Chest box or ribcage is made up of ribs. Between the ribs, there are present inter-costal muscles. The diaphragm is a muscular sheet which partitions the chest and abdomen. The two lungs are covered by a double layered membrane called pleural membrane. There is a thin film of fluid in between the two layers. This watery fluid makes the movements of the lungs (expansion and contraction) easy. It also protects the lungs from external injuries.

iii) Prove with the help of experiment that CO₂ is released during respiration.
Ans: CO₂ Is Released During Respiration:

Principal Theory:
Respiration is a chemical reaction which releases energy from food. The respiratory system exchanges the gases which are involved in respiration.
Respiration by living organisms can be investigated by carrying out experiments to show the production of carbon dioxide and heat.
Lime water can be used to detect carbon dioxide.
If carbon dioxide is bubbled through lime water then it turns from clear to cloudy/milky in colour. That is why lime water is used in a simple respirometer, which can show that more carbon dioxide is present in exhaled air compared to inhaled air.

Material Requireds:

• Respirometer (Cork, Glass tubes and Test tube)
• Syringe
• Lime water

Procedure:

• To prepare respirometer, pass two glass tubes through cork.
• Fix the cork and the mouth of test tubes containing lime water.
• Prepare two apparatus and marked as (A) and (B)
• In (A) respirometer exhaled air through Glass tube into lime water
• In (B) respirometer pass atmospheric air by syringe through Glass tube into lime water.

Observation
Carbon dioxide if passed through lime water turns it milky. This is evident through experiment as:

• (A) when exhaled air passes through the respirometer apparatus containing lime water, the lime water turns milky.
• In (B) when atmospheric air is passed through respirometer apparatus containing the lime-water , the later remains unchanged,
  
  

Conclusion:
Exhaled air contain more carbon dioxide than inhaled air.

iv)Explain the process of ventilation in man.
Ans: PROCESS OF VENTILATION OR BREATHING
The respiratory surfaces are located deep inside the body in the lungs. Air is brought into the lungs from the atmosphere to perform exchange of gases through the process of breathing or Ventilation. The process of breathing consists of two phases:

• Inspiration and
• Expiration.

Inspiration:

1. It is the process through which atmospheric air is directed through the air passage ways up to  the alveoli in the lungs.
2. During inspiration, the diaphragm contracts and becomes flat somewhat and thereby lowering the floor of the thoracic cavity.
3. The external inter-costal muscles contract raising the ribcage. A combined action of these two events expands the thoracic cavity, which in turn expands the lungs.
4. The air pressure within the lungs decreases.
5. Thus air from the environment outside the body is pulled into the lungs (From high pressure to low pressure) to equalize the pressure of both sides.

Expiration:

1. It is just reverse of inspiration. During this process the air moves out from the lungs.
2. The diaphragm relaxes and assumes dome like shape.
3.  During expiration, the external inter-costal muscles relax and the internal inter-costal muscles contract as a result of which ribcage drops.
4. The combined action of these two event decreases the volume of the thoracic cavity (chest) which in turn decreases volume of lungs.
5. The air pressure with in the lungs increases.
6. The air is thus forced out of the lungs.

v) Why smoking is dangerous? How it is related with respiratory disorders?
Ans: Smoking is Dangerous:
Smoking is injurious to human health because the smoke contains many chemical and gases. Dried tobacco leaves are used in cigarettes. The tobacco on burning produces a number of dangerous and toxic compounds. These chemicals and other toxic compounds are responsible for respiratory disorders.

Smoking Cause Respiratory Disorders:
Chemicals Present in Cigarette Smoke and Their Harmful Effects
(a) Nicotine:

1. It damages brain tissues.
2. Causes blood to clot more easily. 3. Harden walls of arteries.

(b) Tar:

1. Kills cells in air passages and in lungs.
2. Increases production of mucous and phlegm in lungs.
3. Causes lung cancer.

(c) Carbon Monoxide:

1. Prevents red blood cells from combining with and transporting oxygen around the body.

(d) Carcinogens:

1. promote the growth of cancerous cells in the body.

(e) Irritants:

1. Irritate air passages and air sacs in the lungs.
2. Kill cells at the surface of air passages.
3. Causes smoker's cough and lung cancer.

EXTRA QUESTIONS:

i)Differentiate between respiration and photo synthesis
Ans: Difference Between Photosynthesis And respiration

S.NO.	Photosynthesis	Respiration
1.	Anabolic process.	Catabolic process.
2.	Synthesis of food from simple, inorganic substances.	Breaking down of food into inorganic substances.
3.	Requires light energy.	Does not require light energy.
4.	Occurs in plants.	Occurs in all living organisms.
5.	Uses carbon dioxide gas.	Uses oxygen gas.
6.	Releases oxygen gas.	Releases carbon dioxide gas.
7.	Takes place during day-time.	Takes place all the times.
8.	Chlorophyll is required.	Chlorophyll not required.

PRACTICAL ACTIVITY

The effect of light on the net gaseous exchange from leaf by using Hydrogen bicarbonate as indicator.
Theory:
Hydrogen bicarbonate is an indicator for carbon dioxide. Its colour turns as follows according to the level of carbon dioxide:

Photosynthesis	Respiration
Highest	Yellow
High	Orange
Atmospheric level	Red
Low	Magenta
Lowest	Purple

Requirements:

• Four test tubes
• Test tube stand
• Aluminum foils or black paper
• Tissue paper
• Fresh green leaves
• Four corks
• Wax
• Thread
• Glass marking
• Pencil

Steps:

1. Mark test tubes as 1, 2, 3 and 4.
2. Fill each test tube quarter full with Hydrogen bicarbonate indicator.
3. Attach each leaf with separate thread and hang one into the test tube 1, test tube 2 and test tube 3.
4. Plug all the tubes with corks and seal them with wax.
5. Wrap tube 2 with aluminum foil or black paper from all side so that light cannot penetrate into this test tube. Similarly wrap test tube 3 with tissue paper.
6. Place all tubes on stand and put the stand in well lighted place.
7. Note and record your observations given below in the table by tick marking the right in the following table:

Observations:

Critical Thinking:
Q.1: Is there any change of coloration of Hydrogen bicarbonate indicator?
Ans: Yes, Hydrogen bicarbonate is an indicator for carbon dioxide. Its colour turns as follows according according to the level of carbon dioxide.

Concentration Of CO2	Colour Of Hydrogen bicarbonate
Highest	Yellow
High	Orange
Atmospheric level	Red
Low	Magenta
Lowest	Purple

Q2. What account for these changes?
Ans: The change in colour of Hydrogen bicarbonate indicator with the different levels of carbon dioxide shows that:
During daytime in the presence of light, when photosynthesis process occurs the concentration of carbon dioxide is lowest because the amount of CO₂ absorbs by plant is greater than the amount of carbon dioxide release during respiration.