Biology For Class X - Chapter No. 2 - Homeostasis - Review Exercise From Text Book

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CHAPTER 2: HOMEOSTASIS
Review Exercise From Text Book

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

A. MULTIPLE CHOICE QUESTIONS
Choose the correct answer:
i) The internal condition of an organism is referred as:
(a) Homeostasis
(b) Internal environment ✓
(c) Internal metabolism
(d) Feedback mechanism

ii) A set of metabolism reaction which maintain internal environment is:
(a) Positive feedback
(b) Negative feedback
(c) Osmoregulation
(d) Homeostasis ✓

iii) Removal of extra liquid water is:
(a) Exudation
(b) Guttation ✓
(c) Respiration
(d) Transpiration

iv) Plant grow near coastal area called:
(a) Xerophyte
(b) Halophyte ✓
(c) Epiphyte
(d) Hygrophyte

v) Organ of human body which is considered on the largest organ is:
(a) Skin ✓
(b) Digestive tract
(c) Liver
(d) Brain

vi) The maintenance of body temperature with in suitable limit is called
(a) Homeotherm
(b) Thermoregulation ✓
(c) Osmoregulation
(d) Heterotherm

vii) The kidney is enclosed in a membrane called
(a) Pericardium
(b) Peritoneum ✓
(c) Pleural membrane
(d) Plumule

viii) The network of blood capillaries present in the layer of skin:
(a) Epidermis
(b) Dermis ✓
(c) Hypodermis
(d) Endodermis

ix) Selective reabsorption in nephron takes place at
(a) Glomerulus
(b) Malpighian body
(c) Convulated tubules
(d) Loop of Henle's ✓

x) The hormone ADH release from
(a) Pituitary gland ✓
(b) Kidneys
(c) Liver
(d) Lungs

B. SHORT QUESTIONS ANSWERS
i) Why homeostasis is required?
Ans: Homeo means same and stasis means state. So Homeostasis is the regulatory mechanism which maintained the internal environment of an organism within suitable limits. It is required to maintain osmoregulation, thermoregulation and also excrete toxic waste from body.
Homeostasis is responsible to maintain optimal conditions for enzyme action throughout the body, as well as all cell functions despite changes in internal and external conditions.

ii) Why plants remove liquid water instead of water vapours?
Ans: The plants remove liquid water in the form of droplet instead of water vapours when there is high atmospheric humidity and less or no transpiration. This process is called guttation. It only occurs at night when water pressure is high in leaves and low temperature environment is present.

iii) How plant survive in Saltish water?
Ans: Some plants grow in sea marshes, oceans or in saltish water. In salty condition water moves outside the cell which is not suitable for plants. To survive in saltish water and to move water from outside to inside the plant develop the following characters.

1. They develop salt glands where they store salts by taking it through active transport.
2. Plants oppose salt to move outside from vacuole.
3. Some salt is accumulated at surface of leaf which attracts water from air.

iv) Why skin is considered as excretory organ?
Ans: Skin is considered as an excretory organ because it plays a very important role in excretion through the production of sweat by sweat glands. It excretes water, salt, and urea from the body through sweat. It is the largest organ of the body, which basically functions as a protective organ but it also works and acts as an excretory organ.

v) What type of structures are present in dermis to perform different functions?
Ans: Dermis is the layer present between epidermis and hypodermis, it contains many different structures. They are as follows:

1. Dermis has nerves ending receptors to detect temperature change, pain, pressure etc.
2. It also contains sweat glands which secrete sweat on the surface to maintain temperature and also secrete urea, water and salt.
3. A network of arterioles is also present in the form of network, which are involved in temperature regulation.
4. The dermis also contains hair follicle and sebaceous glands which secrete oily sebum.

vi) Draw a neat and labelled diagram of nephron.
Ans: NEPHRONS

OR

vii) What is kidney stone?
Ans: A kidney stone is a solid mass that forms from the crystals of calcium oxalate or Calcium Carbonate. Sometimes uric acid and cysteine are also present in it. These molecules separate from urine, precipitate in kidney and deposit in the form of stone. Sometimes these stones are not hard therefore they break into sand like crystals which can pass out of the body with urine without pain. The large size stone however damages the kidney tissues, they may stuck anywhere in urinary tract and cause renal failure with pain.

viii) How human skin maintains temperature in cold conditions?
Ans: The skin is the organ which helps in regulating body temperature. The receptors in skin send nerve impulse to brain in case of increase or decrease in temperature. In cold condition when the body temperature starts decreasing the skin maintains the temperature by following actions:

1. Erection of hairs:
   The muscles contract pulling the hairs upright and trapping a layer of insulating air next to skin.
   
   
2. Vasoconstraction:
   Narrowing of blood arterioles of dermis occur which reduces the blood flow in capillaries of skin so less heat is lost.
   
   
3. Decrease in sweat production:
   The sweat gland stops to produce and secrete sweat, in order to prevent energy loss.
   
   
4. Increase in metabolic rate:
   In cold conditions the rate of metabolism in the organs increases generating more heat which is distributed around the body in the blood stream. It prevents loss through the adipose tissue in hypodermis which work as an insulation layer.

ix) When dialysis is required?
Ans: The patients of kidney failure require dialysis when the donor is not available for kidney transplant. A dialysis machine performs the function of a kidney. It helps to clean the patient's blood from metabolic waste products and toxics. For effective treatment the patient needs to undergo dialysis 2 - 3 times a week. Each session lasts about 3-5 hours depending on the patient's body size and medical condition.

x) Why filtration at Para tabular capillaries called ultra filtration?
Ans: Filtration at Para tabular capillaries i.e. Malpighian tubules is referred to as Ultra filtration because most of the blood plasma is forced out of the glomerulus blood capillaries into Bowman's capsule without any selection. This is a Process of non-selective filtration. Blood is filtered very finely through all the membranes in such a way that all the components of blood passed except proteins.

C. EXTENSIVE RESPONSE QUESTIONS:
i) How skin works as thermoregulatory organ?
Skin Works As Thermoregulatory Organ:
The skin is the organ which help in regulating body temperature .when the receptors in skin detects change in body temperature from set point (set point of human is 37 ℃) i.e. increase or decrease, and then Receptor send nerve impulse to brain. It occurs by feedback mechanism to correct the temperature.

If Body Temperature Start Rise:

1. Production of sweat:
   The sweat gland starts to produce and secrete sweat. The sweat accumulates at the surface of skin and evaporates with heat energy so the body feeling cool.
   
   
2. Laying down of hairs:
   In hot condition, muscles which are attached with hair relax. It allows the hair to lie flat against surface of the skin.
   
   
3. Vasodilation:
   Arterioles found in the form of network in dermis, dilate (become wide) which increasing the flow of blood as well as it brings the blood vessels near the surface of skin which allows more heat loss. This process of vessel dilation is called vasodilation.

In Cold Condition When Body Temperature Starts Decreasing:
In cold condition when the body temperature starts decreasing the skin maintains the temperature by following actions:

1. Erection of hairs:
   The muscles contract pulling the hairs upright and trapping a layer of insulating air next to skin. Now it is not very much effective in human.
   
   
2. Vasocontraction:
   Narrowing of blood arterioles of dermis occurs which reduces the blood flow in capillaries of skin so less heat is lost.
   
   
3. Decrease in sweat production:
   The sweat gland stops to produce and secrete sweat, so it prevent from energy loss.
   
   
4. Increase in metabolic rate:
   In cold conditions the rate of metabolism in the organs increases generating more heat which is distributed around the body in the blood stream. It prevents loss through the adipose tissue in hypodermic which work as an insulation layer.

ii) Describe the urinary system of man with the help of diagram?
Ans: Urinary System In Man
Urinary system of man consist of:

1. A pair of kidney
2. A pair of ureters
3. A urinary bladder
4. A urethra

Kidneys:

• Kidneys are reddish-brown bean shaped organs, situated at the dorsal side of the abdominal cavity on either side of the vertebral column.
• The kidneys lie above the waistline.
• Each kidney has an area in the center of concave surface which faces the vertebral column; this area is called hillus.
• The renal artery, renal vein, nerve and ureter are connected to each kidney at the hillus.
• They are covered by a membrane are called peritoneum.

Ureter:

• The ureter is a narrow tube which connects the kidney to the urinary bladder.
• Urine passes through ureter to the urinary bladder.

Urinary Bladder:

• The urinary bladder is a thin walled muscular pear shaped bag situated towards the bottom of abdominal cavity in front of the rectum which stores urine.

Urethra:

• The urethra is a tube which comes out from the urinary bladder, runs down and opens outside the body through urinary opening (Anus).
• It passes urine from bladder to outside the body.

OR

iii) Describe the structure of Nephron? OR Describe the structure of nephron within the L.S of kidney. 
Ans: Structure Of Nephron:
The structural and functional unit of kidney is called Nephron. Each kidney contains more than one million nephrons, which are microscopic urinary tubules.

Parts of Nephron:
Each nephron is sub-divided into four main parts:

1. Bowman's Capsule
2. Proximal convoluted tubule
3. Loop of Henle's
4. Distal convoluted tubule

1. Bowman's Capsule: 

• In each nephron inner end forms a cup-shaped swelling called Bowman's capsule.
• Each bowman's capsule have a ball of capillaries called glomerulus.
• Bowman's capsule with glomerulus are collectively called Malpighian body or Renal corpuscle.
  
  

2. Proximal Convoluted Tubule: 

• Bowman capsule leads into a short convoluted (coiled) tubule called Proximal Convoluted Tubule which passes into the medulla.
  
  

3. Loop of Henle: 

• The tubule enters into medulla, extends into renal pyramid and makes a U shaped structure called loop of Henle and it goes back into cortex.
  
  

4. Distal Convoluted Tubule:

• When tubule enters the cortex again, it becomes convoluted again.
  
  

Collecting Tubules:

• Number of nephrons opens into a tube called collecting duct.
  
  

Network Of Blood Vessels:

• Nephrons are surrounded by different blood vessels that are connected to the renal artery and renal vein.
  
  

iv) Describe the network of blood vessels found in nephron and their functions.
Ans: Network And Functions of Blood Vessels In Nephron:
Nephrons remove waste materials and excess water from blood and convert them into urine by the process of filtration, reabsorption, secretion and excretion. Nephrons are surrounded by different blood vessels that are connected to the renal artery and renal vein. The blood filter to produce urine in blood capillaries of nephrons as:

1. Afferent Arteriole:
   The renal artery when enters into kidney, it divides into millions of branches called afferent arteriole.
   Function: The blood enters the kidney through renal artery and goes into afferent arteriole.
   
   
2. Malpighian Body:
   Each afferent arteriole further divides into numerous blood capillaries in Bowman's capsule are collectively called glomerulus. The Bowman's capsule with glomerulus is called Malpighian body or renal corpuscles.
   Function: Ultrafiltration occurs at Malpighian body.
   
   
3. Efferent Arteriole:
   Blood leaving the glomerulus through efferent arteriole, enter in blood capillaries surrounding the nephrons.
   Function: these blood vessels carry away filtered blood from glomerulus.
   
   
4. Venule:
   Blood capillaries surround a loop of Henle's unite to form venule, which ultimately joins to form a branch of renal vein.
   Function: It carries filtered blood with less waste materials to the venous system.

v) Describe different disorders of kidney and their treatment?
Ans: Kidney Problems Or Disease:
When the kidneys do not function properly due to different reasons this is referred as Kidney problem or Kidney disease.
There are many problems of kidney:

1. Kidney Stone
2. Kidney Failure

Kidney Stone
A kidney stone is a solid mass that forms from the crystals of calcium oxalate or Calcium Carbonate. Sometimes uric acid and cysteine are also present in it. These molecules separate from urine, precipitate in kidney and deposit in the form of stone. Sometimes these stones are not hard therefore they break into sand like crystals which can pass out of the body with urine without pain. The little large size stone however damages the kidney tissues; it may stuck anywhere in urinary tract and cause renal failure with pain.
Treatment:

1. Lithotripsy:
   If the size of stone is comparatively small we can use the technique of lithotripsy to break stone by ultrasonic waves (sound waves). The broken rudiments drain out from kidney with urine.
2. Renal surgery:
   The large size stone cannot be broken by lithotripsy, so it is removed only by the process of renal surgery.

Prevention:
The large intake of water is the only measure to minimize the chances of formation of stone in kidney.

Kidney failure:
Sometimes the nephrons of kidney are badly damaged and stop working due to certain reason or infection and the kidneys are not able to filter the harmful nitrogenous substance it is called Renal failure Or Kidney failure.
It is mainly due to solute disbalance in blood and kidneys. The failure of kidneys allow urea and other waste materials to accumulate in blood. The amount of H₂O is not regulated also. This dis-balance of solutes causes death unless the patient is given treatment  to filter out wastes by machines.
Treatment of Kidney Failure:

1. Kidney Transplant:
   Patient of kidney failure may get a kidney transplant. In high degree renal failure the surgical transplantation of matching donor kidney is only the option left as the permanent treatment. A person with two healthy kidneys may donate one kidney and survive with one kidney.


2. Dialysis:
   Dialysis machine: A dialysis machine performs the function of a kidney. It helps to clean the patient's blood from metabolic waste products and toxic.
   If a donor is not available, the patient can be treated with dialysis using a dialysis machine. For effective treatment the patient needs to undergo dialysis 2-3 times a week. Each session lasts about 3-5 hours depending on the patient's body size and medical condition.

Source: Special Thanks To Sir Syed Arif Ali

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

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CHAPTER 1: GASEOUS EXCHANGE
Question Answers

Q.1: Define gaseous exchange? Or Why gaseous exchange occur in living organisms?
Ans: All living organism must need to take in oxygen and give out carbon dioxide gases with their environment to carry out their vital functions such as respiration. In addition to respiration, photoautotrophs like plants do carry out the process of photosynthesis by taken in carbon dioxide gases and given out oxygen. This Process of exchange gases in all living organisms is termed as gaseous exchange. Aquatic organisms exchange gases with water while terrestrial one with air.

Q.2: Describe the gaseous exchange in plants?
Ans: Gaseous Exchange In Plants:
Plants exchange gases for the process of photosynthesis and respiration. The process of exchange of gases in plants takes place mainly through minute openings called stomata present in leaves. The roots and stem do exchange gases for respiration.

Photosynthesis: During the process of photosynthesis, carbon dioxide is taken in while oxygen is given out. During daytime (i.e. in the presence of sunlight), green parts (contain chlorophyll) of the plants carry out the process of Photosynthesis to prepare complex food molecules (organic molecules) by utilizing simple molecules such as carbon dioxide gas and water. During this process, carbon dioxide gas is taken in while oxygen gas is released as a by-products is given out.

Respiration: In respiration, oxygen is taken in and carbon dioxide is given out. Respiration takes place in all living cells. It is the process in which food is oxidized to release energy. In aerobic respiration, it involves taking in oxygen and giving out carbon dioxide.

Q.3: Define respiration and photosynthesis? and Differentiate between respiration and photosynthesis
Ans: DEFINITIONS:
Photosynthesis:
During daytime, green parts of the plants carry out the process of Photosynthesis to prepare complex food molecules (organic molecules) by utilizing simple molecules such as carbon dioxide gas and water in the presence of sunlight and chlorophyll. During this process, carbon dioxide gas is taken in while oxygen gas is released as a by-product is given out.

Respiration:
In respiration, oxygen is taken in and carbon dioxide is given out. Respiration takes place in all living cells. It is the process in which food is oxidized to release energy.

Glucose + Oxygen → Carbon dioxide + water + Energy
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

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.

OR

S.NO.	Photosynthesis	Respiration
1.	An anabolic process in which synthesis of food (carbohydrate) occurs from simple inorganic substances.	A catabolic process in which breaking down of food (carbohydrate) occurs into inorganic substances.
2.	It occurs in plants. During day time carbon dioxide is taken in and oxygen is given out.	It occurs in all living organisms. This process occur all the time in which oxygen is taken in and carbon dioxide is given out.
3.	Light energy and chlorophyll are required.	Light energy and chlorophyll are not required.

Q.4: Define Stomata? OR What are stomata? What function do they perform in photosynthesis?
Ans: Stomato (Singular “Stomo’ means ‘mouth):
There are microscopic openings present in the epidermis of leaves called stomata. Through these openings, plants exchange gases with their environment. Each stoma is a slit-like opening formed by two special cells called guard cells. They are chlorophyll containing cells with thicker inner while thinner and elastic outer cell walls. The opening and closing of stomata depend upon the turgidity of the guard cells.

Function Of Stomata In Photosynthesis Process:
During the daytime, as a result of the ongoing process of photosynthesis, the accumulation of photosynthetic solutes causes an 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.

Q.5: Describe gaseous exchange in animals?
Ans: Gaseous Exchange In Animals:
Animal do exchange gases with their environment for the respiration process. To obtain energy from food, they take in oxygen and give out carbon dioxide. So, the process of gaseous exchange is ultimately linked with respiration.
The respiratory medium for aquatic animals is water whereas for terrestrial animals is air. The amount of molecular oxygen present in the air is about 21% while in water it is about 5%.

Q.6: What is respiratory surface? Write its properties and also describe proportion of the respiratory surface in animals?
Ans: Respiratory Surface:
Respiratory surface is the area where gaseous exchange occurs in body. Examples gills, trachea, lungs etc.
To exchange gases, animals have respiratory surface. In unicellular organisms like Protozoa, the plasma membrane serves as the respiratory surface. In multicellular animals, the body surface or some internal surface could serve as the respiratory surface.

Properties of Respiratory surface In Animals:

• Thin
• Wet
• Permeable
• Large in relation to the volume of the body.

The Proportion Of Respiratory Surface In Animals:
It must be sufficient large enough for exchange gases for all the cells of the body. For example, the total surface area of the respiratory surface in humans is about 20 times the size of the body.

Q.7: What are the effects of large respiratory surfaces in animals?
Ans: Effects Of Large Respiratory Surfaces In Animals:
An increased surface for gaseous exchange allows a faster rate of diffusion to supply oxygen and remove carbon dioxide It is also necessary to compensate for the small surface area to volume ratio of the animal body.

Q.8: How many processes are involved in human respiration?
Ans: Processes Involved In Human Respiration:
In human, the process of respiration involves:

• breathing,
• gaseous exchange and
• cellular respiration

Like other terrestrial vertebrates, our respiratory surface is located inside the body in the form of alveoli contained in paired organs, lungs.

Q.9: Define respiratory system? Describe the human respiratory system in detail? Also draw well-labeled diagram Of human respiratory system?
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 membranes: 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

Q.10: 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

Q.11: Briefly describe the gaseous exchange in alveoli?
Ans: Gaseous Exchange in Alveoli:
The gaseous exchange takes place at the level of alveoli. Oxygen brought in by air is taken up by the haemoglobin of RBCs of blood and vice versa. The carbon dioxide brought by the blood is given out to the air present in alveoli. This gaseous exchange involves diffusion which becomes possible at this level because both alveolus ad blood capillaries are only one cell layer in thickness.

Q.12: Write down the composition of inspired and expired air?
Ans: Composition Of Inspired and Expired Air:

Components %	Inspired Air	Expired Air
Oxygen	About 61	About 16
Carbon dioxide	About 0.03	About 4
Nitrogen	About 79	About 79
Water Vapour	Variable	Saturated
Temperature	Atmospheric temperature	37 degree Celsius

Q.13: Prove with the help of experiment that CO₂ is released during respiration. OR How can we demonstrate the release of carbon dioxide during expiration?
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.

Q.14: Distinguish between inspiration and expiration.
Ans: Difference Between Inspiration And Expiration

S.NO.	INSPIRATION	EXPIRATION
1.	Inspiration is the intake of the air (oxygen) into the lungs.	Expiration is the expulsion of the air (carbon dioxide) out of the lungs.
2.	Inspiration is an active process.	Expiration is a passive process.
3.	The external intercostals muscles are contracted and internal intercostals muscles are relaxed.	The external intercostals muscles are relaxed and internal intercostals muscles are contracted.
4.	Rib cage moves forward and outward.	Rib cage moves downward and inward.
5.	The diaphragm moves down by contracting and become flat.	The diaphragm moves up by relaxing and becomes original dome shaped.
6.	The size of the thoracic cavity increases.	The size of the thoracic cavity decreases.
7.	The air pressure inside the lungs decreases due to the increase of volume of the chest cavity.	The air pressure inside the lungs increases due to the decrease of volume of the chest cavity.
8.	This process is also called inhalation.	This process is also called exhalation.

Q.15: Why do we deep breathe during or immediately after exercise? Or Why rate of breathing change with different conditions? OR What will be the rate of breathing at rest or during 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. It is termed as "anaerobic respiration". As a result of this, lactic acid is formed in the muscles rather than carbon dioxide. It causes pain and cramps in normal muscles. The breaking down of lactic acid requires additional amount of oxygen. The extra amount of oxygen is obtained through deep breathes.

Q.16: Define 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 arising 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.

Q.17: What is artificial ventilator? Illustrate its process?
Ans: Artificial ventilator:
It is a machine that works like lungs when patient's natural breathing becomes difficult. Through this machine, the oxygen rich air is directly supplied to the trachea through a tube inserted in the mouth up to the windpipe.

Process Of Artificial Ventilator:

Q.18: Describe respiratory disorder?
Ans: RESPIRATORY DISORDERS Or DISORDERS OF RESPIRATORY SYSTEM:
1. 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.
Treatment: Bronchitis is treated by using antibiotics, bronchodilator oxygen therapy and anti-inflammatory drugs.

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.
Treatment: Its effect is permanent and irreversible however if a person is stop smoking soon, further damage might be reduced.

3. PNEUMONIA: It is an infectious disease.
Cause: It usually caused by special bacteria, viruses or fungi.
Symptoms: In pneumonia, the alveoli are infected so they may be filled with fluid or pus. The breathing becomes difficult. The patient suffers from fever, cough, chill and chest pain.
Treatment: Antibiotics are used for its treatment.

4. ASTHMA: It is an inflammatory condition of airways of lungs.
Cause: Asthma is actually an allergic response to pollen dust, smoke, fur, feathers and number of other substances. It may obstruct the airways making it difficult to breath for its patient.
Symptoms: It is characterized by shortness of breath, chest pain, fever, wheezing sound during expiration and cough.
Treatment: It can be treated by using cough syrups, anti-inflammatory drugs, allergy medication and bronchodilators.

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.
Treatment: The patient of lung cancer is given one or more treatments, including: surgery, chemotherapy and radiation.

Q.19: Define Guard cell?
Ans: Guard Cells:
Each stoma is formed by two special cells called guard cells. They are chlorophyll containing cells with thicker inner while thinner and elastic outer cell walls. The opening and closing of stomata depend upon the turgidity of the guard cells.

Q.20: Give the death ratio due to air pollution?
Ans : Death Ratio Due To Air Pollution:

PRACTICAL ACTIVITY

Q.21: Explain the effect of light on the net gaseous exchange from leaf by using Hydrogen bicarbonate as indicator through experiment.
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:
(i) 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 to the level of carbon dioxide.

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

(ii) 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.
While at night in the absence of light only respiration process takes place, so the concentration of carbon dioxide is higher.

Source: Special Thanks To Sir Syed Arif Ali

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

GO TO INDEX
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

UNIT 01: PROBLEM SOLVING AND ALGORTHM DESIGNING - Chapter From Text Book - Computer Science For Class X

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Computer Science For Class X
Unit 01: Problem Solving And Algorithm Designing
Chapter From Text Book