Biology For Class X - Chapter No. 1 - Gaseous Exchange - Review Exercise From Text Book

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CHAPTER 1: GASEOUS EXCHANGE
Review Exercise From Text Book

By Mrs. Ayesha Arif
Vice Principal
(Jauhar Progressive School)

A. MULTIPLE CHOICE QUESTIONS

Choose the correct answer:
i) The biological functions which perform gaseous exchange:
(a) Photosynthesis
(b) Respiration
(c) Both a and b ✓
(d) Growth

ii) Plants do exchange of gases through:
(a) Roots
(b) Stomata (c) Stem
(d) All of these ✓


iii) Each stoma is formed by:
(a) one guard cell
(b) two guards cells ✓
(c) three guard cells
(d) four guard cells

iv) Respiratory surface possesses following property:
(a) thin and wet
(b) permeable
(c) very large
(d) all of these ✓

v) Inspiration involves:
(a) Contraction of intercostals muscles
(b) contraction of diaphragm
(c) Inward movement of ribs
(d) Both a and b ✓

vi) Larynx is located on:
(a) Lungs
(b) Trachea ✓
(c) Bronchus
(d) Bronchiole

vii) The respiratory surface of human is:
(a) Nostril
(b) Bronchiole
(c) Alveoli ✓
(d) Trachea

viii) Increase in rate of breathing is due to the following:
(a) increase CO₂ in blood ✓
(b) Increase O₂ in blood
(c) decrease CO₂ in blood
(d) decrease O₂ in blood

ix) Which of the following disorder is associated with degeneration of alveoli?
(a) Bronchitis
(b) Lung cancer
(c) Asthma
(d) Emphysema ✓

x) Which of the following disorder is associated with inflammation of air passage ways?
(a) Bronchitis ✓
(b) Lung cancer
(c) Asthma
(d) Emphysema

B. SHORT QUESTIONS

i) Why the stomata generally open during day-time?
Ans: During daytime, as a result of ongoing process of photosynthesis, the accumulation of photosynthetic solute causes increase in turgidity of the guard cells. Thus stomata are opened and the process of taking in carbon dioxide and giving out of oxygen begins until it becomes dark.

OR

The stomata control gas exchange in the leaf. Each stoma is surrounded by two guard cells. The stomata can be opened or closed, depending on the turgidity of its guard cells. In the light, during the ongoing process of Photosynthesis the guard cells absorb water by osmosis, become turgid and thus the stoma opens. In the dark, the guard cells lose water, become flaccid and the stoma closes.

OR

Stomata are mouth-like cellular microscopic openings present in the epidermis of leaves that regulates exchange of gases between plants and atmosphere. In leaves, during day time osmotic pressure of guard cells increases, water enters into it and makes stomata open to favour carbon dioxide diffusion when light is available for photosynthesis. In night, osmotic pressure decreases, water moves out and makes the stomata close due to which stomata becomes more flaccid to limit transpiration and save water.

ii) Which parts of the plant intake CO₂ and give out O₂ , take in O₂ oxygen and give out CO₂ during day-time?
Ans: The exchange of oxygen and carbon dioxide in the leaf (as well as the loss of water vapours in transpiration) occurs through pores called stomata (singular = stoma) present in leaves.
Plants get energy by the process of respiration. All the parts of plants perform respiration individually whole day. The roots of plants take in oxygen and give out carbon dioxide for respiration from the air present in between the soil particles by the process of diffusion.
During day time, in plants exchange of gases occur through the process of photosynthesis in which carbon dioxide is taken in and oxygen is given out. As carbon dioxide is used for photosynthesis and hence there is no release of CO₂ in day time.

OR

Photosynthesis: Plants take in CO₂ and give out O₂ during the process of Photosynthesis in the day time . Photosynthesis occurs because of the green parts of the plant, mainly leaves. Therefore leaves are responsible for taking in CO₂ and giving out O₂ through microscopic openings called stomata present in the epidermis of leaves. 
Respiration: While on the other hand the taking in of O₂ and giving out CO₂ happens during the process of respiration whole day. Exchange of gases during respiration involves roots and stem of the plant in day time. But during daytime, the amount of carbon dioxide released is negligible as compared to the amount of oxygen produced as a result of photosynthesis.

OR

During day time along with respiration, photosynthesis process is also occur in plants because of the green parts of the plant, mainly leaves. Therefore leaves of plants take in CO₂ and give out O₂ due to photosynthesis process during daytime through stomata which are the microscopic openings present in the epidermis of leaves.
While respiration takes place in all parts of the plants day and night. So, in day time roots and stem of plants take in O₂ and give out CO₂. But during daytime, the amount of carbon dioxide released is negligible as compared to the amount of oxygen produced as a result of photosynthesis.

iii) Why do we have to breathe through nostrils rather than oral cavity?
Ans: It is better to breathe through nostrils rather than oral cavity because 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. On the other hand oral cavity has no medium to filter air and it also makes the mouth dry.

OR

We have breathed through nostrils (nose) rather than the oral cavity (mouth) because our nose helps us to breathe safely, efficiently and properly. Nose has ability to:

• Filter Out Foreign Particles: Nasal hairs filter out dust, allergens and pollen, which help to prevent them from entering our lungs.
• Humidified Inhale: Air: Ciliated epithelial lining and mucous in nasal cavity moisturize and warm inhaled air to body temperature. So making it easier for our lungs to use.
• Produce Nitric Oxide: During nasal breathing, our nose releases nitric oxide is vasodilator, which helps to widen blood vessels. This help to improve oxygen circulation in our body.

On the other hand, breathing through oral cavity (mouth) has some health risks. It can dry out our mouth that increase risk of:

• inhaling unfiltered hair
• allergic reactions
• asthma
• bad breath
• tooth decay
• gum inflammation
• snoring
• sleep apnoea
• teeth or jaw abnormalities

iv) Differentiate between breathing, gaseous exchange and respiration.
Ans: Difference Between Gaseous Exchange, Breathing And Respiration

S.NO.	Gaseous Exchange	Breathing	Respiration
1.	Gas exchange is the physical process by which gases move passively by diffusion across a gaseous exchange surface.	Breathing is also a physical process by which air is passed to a gaseous exchange surface. It involves inhaling and exhaling.	Respiration is a metabolic process (chemical) where the oxygen is used to break the glucose into energy  to be later used by the cells of the body.
2.	It is used for the exchange of oxygen and carbon dioxide between an organism and its environment .	In it oxygen is taken in and carbon dioxide is given out.	Complex organic compounds are converted into simple one. i.e. glucose into CO2 and water and energy is released.
3.	It involves the movement of gases from a surface of higher concentration to a surface of lower concentration. No energy require.	During breathing, there is no energy production.	Energy is produced during the respiration process in the form of ATP
4.	Aquatic organisms exchange gases with water while terrestrial ones with air.	It is an extracellular process as it takes place outside the cells.	This is basically an intracellular process that takes place in the cells.
5.	Enzymes are not used in gaseous exchange.	Enzymes are not in use at the time of breathing.	Enzymes are used in large numbers.
6.	Gaseous exchange in plants is done through roots, stems and stomata in the leaves (photosynthesis). While in animals it occurs through alveoli in lungs.	Complex organic compounds are converted into simpler one e.g..

v) Why do we deep breathe during or immediately after exercise?
Ans: We deep breathe during and immediately after exercise because the rate of breathing changes automatically according to the changes in internal or external conditions.
Breathing is largely an involuntary process. It is regulated by hypothalamus of our brain. When we are doing exercise our muscles work harder, rate of breathing would increase because of increased consumption of oxygen by our muscles. Thus gradually increase in concentration of carbon dioxide in our blood will cause an increase our breathing rate.
If the exercise condition persists, the muscle cells will start breaking down glucose without oxygen. As a result of this, lactic acid is formed in the muscles rather than carbon dioxide. The breaking down of lactic acid requires additional amount of oxygen. The extra amount of oxygen is obtained through deep breathes.

vi) What is "oxygen debt"?
Ans: OXYGEN DEBT:
During exercise, the muscle cells start breaking down glucose without oxygen. As a result of this , lactic acid is formed in the muscles rather than carbon dioxide. The breaking down of lactic acid requires additional amount of oxygen. That extra amount is called oxygen debt and is obtained through deep breathes.

OR

A temporary oxygen shortage in the body tissues is arisen from exercise. In this condition break down of lactic acid requires additional amount of oxygen which is termed as "oxygen debt". The extra amount of oxygen is obtained through deep breathes.

vii) Distinguish between inspiration and expiration.
Ans: Difference Between Inspiration And Expiration

S.NO.	INSPIRATION	EXPIRATION
1.	Inspiration is the intake of the air into the lungs.	Expiration is the expulsion of the air out of the lungs.
2.	Inspiration is an active process.	Expiration is a passive process.
3.	In inspiration, the external intercostals muscles are contracted and internal intercostals muscles are relaxed.	In expiration, the external intercostals muscles are relaxed and internal intercostals muscles are contracted.
4.	In inspiration, rib cage moves forward and outward.	In expiration, the rib cage moves downward and inward.
5.	In inspiration, the diaphragm contracts and flattens.	In expiration, the diaphragm relaxes and becomes original dome shaped.
6.	In inspiration, the size of the thoracic cavity increases.	In expiration, the size of the thoracic cavity decreases.
7.	In inspiration, the air pressure in lungs is less than the atmospheric pressure.	In expiration, the air pressure in the lungs is higher than the atmospheric pressure.

viii) What is lung cancer?
Ans: LUNG CANCER:
Lung cancer is a respiratory disease, more common in men than women. In it abnormal cells appear in lungs which may spread to other tissues. It can cause lumps, masses or tumors to grow in the lungs. It may start in the lining of the bronchi or it may be in other areas of the lungs.

Causes:

1. Smoking
2. Industrial carcinogens
3. Air pollution

Main cause of any cancer is a carcinogen, ionizing radiation, and viral infection. Smoking is the main contributor to lung cancer. Cigarette smoke contains over 69 known carcinogens.

Symptoms:

1. Cough with sputum
2. Breathlessness (shortness of breath)
3. Pleural chest pain
4. Repeated Lung infections
5. Weight loss
6. Bone ache
7. Hoarseness
8. Weakness
9. Fatigue etc.

In the early stages, lung cancer does not show any symptoms. However, in the advanced stage when it has fully spread, it is very painful and incurable and becomes fatal.

Treatment:
The patient of lung cancer is given one or more treatments, including:

• surgery
• chemotherapy and
• radiation therapy

ix) How the asthma is characterized?
Ans: Asthma is an inflammatory condition of airways of lungs. It is characterized by:

1. shortness of breath
2. chest pain
3. fever
4. wheezing sound during expiration and cough.

Asthma is actually an allergic response to pollens, dust, smoke, fur, feathers and number of other substances. It may obstruct the air-ways making it difficult to breath for its patient.

x) Name five animals which use their body surface for gaseous exchange.
Ans: The animals which use their body surface for gaseous exchange are:

1. Flatworms
2. Annelids (i.e. Earthworms)
3. Leech
4. Sabella
5. Tapeworm
6. Frog & Toads
7. Salamanders
8. Sea Snake
9. Turtles
10. Fish
11. Insects (grasshopper)
12. Octopus
13. Amoeba and paramecium also respire from their body surface and this type of respiration is also known as cell surface respiration.

C. EXTENSIVE RESPONSE QUESTIONS:

i) What measures would you take to avoid respiratory disorders?
Ans: Measures To Avoid Respiratory Disorder:
Our body has a natural defence system to protect the respiratory system especially the lungs, by keeping dirt and germs away. But to reduce our risk of respiratory disorders and lung disease the following measures should be taken.

1. Don't Smoke:
   Cigarette smoking is the major cause of lung cancer and chronic obstructive pulmonary disease, which includes chronic bronchitis and emphysema. Cigarette smoke can narrow the air passages and difficulty in breathing. It causes chronic inflammation or swelling in the lung. So, it would be better if we don't smoke or quit smoking as soon as possible.
   
   
2. Avoid Exposure To Indoor Pollutants:
   Secondhand smoke, chemicals in the home and workplace, and radon all can cause or worsen lung disease. We should make our homes and car free from such pollutants or contaminants. We must test our home for radon. Be mindful of our environment's air quality.
   
   
3. Avoid Exposure To Outdoor Air Pollutants:
   The air quality outside can vary from day to day and sometimes is unhealthy to breathe. Useful strategies to minimize prolonged exposure can help keep us and our family well. Avoid to do exercise outdoors in bad air. Climate change and natural disasters can also directly impact lungs.
   
   
4. Prevent Infections:
   A cold or other respiratory infection can sometimes become very serious. To protect our self we should:
   * Wash hands often with soap and water.
   * Avoid crowd during cold and flu season.
   * Take care of dental health and oral hygiene to prevent harmful bacteria, travelling from mouth to upper airway to  prevent infections. Brush teeth twice daily.
   * Get vaccinated every year against influenza and other diseases.
   * Stay home if sick to avoid spreading colds and respiratory illnesses to others.
   
   
5. Get Regular Check-Up:
   Get regular check-ups to prevent diseases, even feeling well, especially for lung diseases. Because lungs diseases sometime undetected until it is serious.
   
   
6. Exercise:
   We should exercise regularly. Practice deep breathing, or diaphragmatic breathing, or cardiovascular exercise to boost lung fitness and overall health.

ii) Discuss human respiratory system with the help of suitable illustration?
Ans: Respiratory System:
The system which is responsible for the exchange of gases (oxygen is taken in and carbon dioxide is given out) between the body and the environment is called respiratory system.

Human Respiratory System:
Our respiratory system consists of:

• Paired lungs located inside the thoracic (chest) cavity and
• Air passageways

LUNGS:

• There is a pair of lungs present in the chest cavity in man. Each lung is soft, spongy and pinkish in appearance.
• Pleural Membrane: Lungs are wrapped in two Pleural membranes. The space between pleural membranes is filled with fluid that acts as a lubricant. This watery fluid makes the movements of the lungs (expansion and contraction) easy. This makes breathing movements easier. It also protects the lungs from external injuries.
• Lungs are enclosed in a protected bony cage made up of a flat sternum in front, 12 pairs of ribs from front to back where the vertebral column is present.
• Ribs are attached with intercostal muscles.
• Diaphragm: In the lower part of the thorax, lies a sheet of muscles called Diaphragm which separates it from the abdominal cavity.
• Each lung is made up of millions of alveoli.
  

Lung Capacity:
Like a balloon, lungs can be filled with a maximum amount of 5 liters of air. Surprising, we use normal about ¹/₂ of the air coming into the lungs.

Alveoli:
The walls of the respiratory bronchioles have clusters of tiny air sacs are called alveoli (singular: alveolus). Each alveolus is the respiratory surface. It's a pouch-like microscopic structure made up of only one layer of cells. It's enclosed by a dense capillary network. In each alveolus, the exchange of gases takes place between air and blood through capillary network.

THE AIR PASSAGEWAY:
The air passageway consists of:

• Nose (Nostril)
• Pharynx
• Larynx
• Trachea
• Bronchi and
• Bronchioles.

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.

Nose (Nostril):

• Air from outside enters into the nasal sacs through external nostrils. 
• The hairs in nasal sacs as well as ciliated epithelial lining and mucous keep the air cleans by trapping and removing dust and germs. This ensures clean air 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 extends from behind the nasal cavities to the opening of esophagus and larynx.
• The air goes from the pharynx into the larynx.

Larynx:

• At the beginning of trachea, there is a cartilaginous box called larynx or sound box, containing vocal cords to produce sound.
• Glottis: The opening of the larynx is known as glottis.
• Epiglottis: Glottis has a lid like cover, epiglottis. During swallowing food or drink, the epiglottis closes the glottis to prevent any food to enter the trachea.

Trachea:

• Larynx opens into a long tube air tube (wind pipe) called Trachea.
• It is about 12 cm long and lies in front of the oesophagus.
• The trachea has incomplete C-shaped cartilaginous rings which prevent it from collapsing 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:

• Trachea in the center of the thorax bifurcates into two smaller ducts or Bronchi. Each bronchus  have C-shaped cartilaginous rings.
• The bronchus of each side enters into the respective lung. As soon as enters into the lung, it breaks up into many smaller ducts or bronchioles.
• 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.

Bronchiole:

• The secondary bronchi further divide into very fine and thin branches (tubes) called bronchioles.
• The bronchioles do not have cartilaginous plates in their walls. They have smooth muscle and elastic fibers.
• Each bronchiole opens into air sacs or alveoli.

OR

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 Required:

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

Procedure:

• To prepare respirometer, pass two glass tubes through cork.
• Fix the cork at 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 (or breathing) in man?
Ans: Ventilation or Breathing:
Ventilation or breathing is largely involuntary process, It is regulated by hypothalamus of our brain. It is the movement of air through the conducting passages between the atmosphere and the lungs. The air moves through the passage because of pressure gradient that are produced by the contraction of the diaphragm and thoracic muscles.
Pulmonary respiration is commonly referred to as breathing. It is the process of air flowing into the lungs during inspiration (inhalation of oxygen from the environment) and air flowing out of the lungs during expiration (exhalation of carbon dioxide back into environment). Air flows because of pressure differences between the atmosphere and the gases inside the lungs.

Process of Breathing:
The respiratory surfaces are located deep inside the body in the lungs. So in order to perform the exchange of gases, the air must first be brought into the lungs from the atmosphere. It is achieved through the process of breathing or ventilation. The process of breathing consists of two phases:

1. Inspiration Or Inhalation and
2. Expiration Or Exhalation

Inspiration Or Inhalation:

• It is the process through which atmospheric air is directed through the air passageways up to the alveoli in the lungs. It involves the contraction of:
  * external intercostal muscles that raising the rib-cage and
  * the diaphragm that becomes flattened by lowering the floor of the thoracic cavity.
• As a result, the volume of the thorax (chest) is increased thereby decreasing the pressure of air within the lungs.
• So the external air rushes inside from high pressure to low pressure. The lungs gets expanded in this way.

Expiration Or Exhalation:

• It is just the reverse of inspiration. During this process, the air moves out from the lungs.
• Both, intercostal muscles and diaphragm are relaxed. This moves the ribs inside and the diaphragm resume dome like shape.
• Both the activities depress the chest inside. The volume of the thoracic cavity (chest) is decreased causing an increase in the pressure on the lungs.
• This forces the air present in the lungs to outside through the body.

OR

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 or cigar. The tobacco on burning produces a number of dangerous and toxic compounds. These chemicals and other toxic compounds are responsible for respiratory disorders.
According To Medical Reports:

• Diseases caused by smoking kill 6 millions people worldwide every each year.
• Smoking causes almost 90% of death from lung cancer and chronic obstructive pulmonary diseases (COPD).

RISK LINKED TO SMOKING:
1. Chronic Bronchitis: This is a type of COPD. The long-term (chronic) inflammation of the air passageways is termed as Bronchitis.
Cause: It is caused either by smoking or by some bacteria.
Symptoms: It is characterized by cough, increased mucous secretion, shortness of breath and low fever.

2. Emphysema: This is also a type of COPD. It is related to the progressive destruction to the alveoli.
Cause: It occur due to long term exposure usually to the industrial pollutants or smoking.
Symptoms: It is characterized by laborious breathing. It causes cough with phlegm production and extreme tiredness (fatigue). It can also cause sleeping and heart problems, weight loss and depression.

5. Lung Cancer: Lung cancer is a respiratory disease, more common in men than women. In it abnormal cells appear in lungs which may spread to other tissues. It can cause lumps, masses or tumors to grow in the lungs. It may start in the lining of the bronchi or it may be in other areas of the lungs.
Causes: Smoking, Industrial carcinogens, Air pollution.
Main cause of any cancer is a carcinogen, ionizing radiation, and viral infection. Smoking is the main contributor to lung cancer. Cigarette smoke contains over 69 known carcinogens.
Symptoms: Cough with sputum and blood, breathlessness (shortness of breath), pleural chest pain, repeated lung infections, weight loss, bone ache, hoarseness, weakness, fatigue etc.
In the early stages, lung cancer does not show any symptoms. However, in the advanced stage when it has fully spread, it is very painful and incurable and becomes fatal.

Other Types Of Cancer: Smoking increases the risk of the nose, sinuses, voice box and throat. It also increases the risk of many other cancers like cancer of gastrointestinal, urinary and female reproductive system.

Dangers Of Secondhand Smoke:
Second-hand smoke is smoke that is breathed out by smokers. It is also smoke from burning cigarettes, cigar or pipes. It causes more than 41,000 deaths per year. It can also lead to lungs and heart diseases. Symptoms linked to second-hand smoke may include:

• Eye. nose and throat irritation
• Coughing
• Too much mucus in the nose.
• Chest discomfort or pain

Children and babies exposed to second hand smoke are more likely to get ear-infection and asthma. They are also at a higher risk for sudden infant death syndrome (SIDS).

Chemicals Present in Cigarette Or Cigar 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.

Source: Special Thanks To Sir Syed Arif Ali