Topic Class 10 Biology Chapter 10: Gaseous Exchange Complete Study Notes
1. Introduction
Gaseous exchange is the process of taking in oxygen and giving out carbon dioxide. In humans,
this process is carried out by the Respiratory System, which consists of two main parts: the Air
Passageway and the Lungs.
2. The Air Passageway
The air passageway consists of the parts through which the outside air comes into the lungs
and, after gaseous exchange, goes out.
Nasal Cavity: Air enters through the nostrils into the nasal cavity. It has fine hairs and mucus
which filter dust particles and warm the air.
Pharynx: A muscular passage common to both food and air.
Larynx (Voice Box): A box made of cartilage located between the pharynx and trachea. It
contains vocal cords that produce sound.
Trachea (Windpipe): A tube about 12 cm long that lies in front of the esophagus. It has
C-shaped cartilaginous rings to prevent it from collapsing.
Bronchi & Bronchioles: The trachea divides into two bronchi, which further divide into fine tubes
called bronchioles.
Alveoli: Bronchioles end in tiny air sacs called Alveoli. This is the actual site of gaseous
exchange.
3. The Mechanism of Breathing
Breathing is a physical process that involves two phases:
A. Inspiration (Inhalation)
Rib Muscles: Rib muscles contract and ribs are raised.
Diaphragm: The dome-shaped diaphragm contracts and moves downwards.
Chest Cavity: The area of the chest cavity increases, reducing air pressure.
Result: Air from outside rushes into the lungs.
B. Expiration (Exhalation)
Rib Muscles: Rib muscles relax and ribs move downwards.
Diaphragm: The diaphragm relaxes and gets its dome shape back.
Chest Cavity: The space in the chest cavity decreases, increasing pressure on the lungs.
Result: Air is pushed out of the lungs.
4. Respiratory Disorders (Common Problems)
Bronchitis: Inflammation of the bronchi or bronchioles.
Pneumonia: An infection of the lungs. If it affects both lungs, it is called double pneumonia.
Asthma: A form of allergy that causes inflammation of the bronchi, leading to difficulty in
breathing.
Lung Cancer: Uncontrolled cell division in the tissues of the lung, often caused by smoking.
5. Important Key Points for Exams
Stomata: Small pores in leaves for gaseous exchange in plants.
Lenticels: Small pores in the bark of woody stems.
6. Gaseous Exchange in Plants (Plants )میں گیسوں کا تبادلہ
, Plants do not have a specialized respiratory system like humans. They exchange gases through
various methods:
Stomata: Most gaseous exchange occurs through stomata in the leaves and young stems.
Lenticels: In woody stems and mature roots, exchange occurs through tiny pores called
lenticels.
Roots: Gas exchange also takes place through the general surface of young roots.
7. Structure of the Lungs ()پھیپھڑوں کی ساخت
The Lungs: Humans have a pair of lungs in the chest cavity. The left lung is slightly smaller
(two lobes) and the right lung is bigger (three lobes).
Pleural Membranes: Each lung is enclosed by two membranes called outer and inner pleural
membranes.
Diaphragm: Below the lungs is a thick muscular structure called the diaphragm.
8. Detailed Comparison: Inhaled vs Exhaled Air.
Feature Inhaled Air (Inside) Exhaled Air (Outside)
Oxygen 21% 16%
Carbon Dioxide 0.04% 4%
Nitrogen 79% 79%
Water Vapours Variable Saturated
9. Frequently Asked Questions (Important for Exams)
Q1: Define Cellular Respiration?
Ans: The process in which C-H bonds in food are broken by oxidation-reduction reactions and
energy is transformed into ATP.
Q2: What is the role of Mucus in the Nose?
Ans: Mucus moistens and warms the air while trapping dust particles.
Q3: What is Nicotine?
Ans: Nicotine is a powerful poison found in cigarettes that damages the central nervous system
and causes addiction
Biology Class 10: Chapter 11
Topic: Homeostasis ()ہومیو سٹیسس
1. Introduction to Homeostasis
Homeostasis is the maintenance of the internal conditions of the body at equilibrium, despite
changes in the external environment.
Example: The human body temperature is maintained at about 37°C.
Key Processes:
Osmoregulation: Maintenance of water and salts in body fluids.
Thermoregulation: Maintenance of internal body temperature.
Excretion: Removal of metabolic wastes from the body.
2. Homeostasis in Plants
Plants also maintain their internal environment using various mechanisms:
1. Introduction
Gaseous exchange is the process of taking in oxygen and giving out carbon dioxide. In humans,
this process is carried out by the Respiratory System, which consists of two main parts: the Air
Passageway and the Lungs.
2. The Air Passageway
The air passageway consists of the parts through which the outside air comes into the lungs
and, after gaseous exchange, goes out.
Nasal Cavity: Air enters through the nostrils into the nasal cavity. It has fine hairs and mucus
which filter dust particles and warm the air.
Pharynx: A muscular passage common to both food and air.
Larynx (Voice Box): A box made of cartilage located between the pharynx and trachea. It
contains vocal cords that produce sound.
Trachea (Windpipe): A tube about 12 cm long that lies in front of the esophagus. It has
C-shaped cartilaginous rings to prevent it from collapsing.
Bronchi & Bronchioles: The trachea divides into two bronchi, which further divide into fine tubes
called bronchioles.
Alveoli: Bronchioles end in tiny air sacs called Alveoli. This is the actual site of gaseous
exchange.
3. The Mechanism of Breathing
Breathing is a physical process that involves two phases:
A. Inspiration (Inhalation)
Rib Muscles: Rib muscles contract and ribs are raised.
Diaphragm: The dome-shaped diaphragm contracts and moves downwards.
Chest Cavity: The area of the chest cavity increases, reducing air pressure.
Result: Air from outside rushes into the lungs.
B. Expiration (Exhalation)
Rib Muscles: Rib muscles relax and ribs move downwards.
Diaphragm: The diaphragm relaxes and gets its dome shape back.
Chest Cavity: The space in the chest cavity decreases, increasing pressure on the lungs.
Result: Air is pushed out of the lungs.
4. Respiratory Disorders (Common Problems)
Bronchitis: Inflammation of the bronchi or bronchioles.
Pneumonia: An infection of the lungs. If it affects both lungs, it is called double pneumonia.
Asthma: A form of allergy that causes inflammation of the bronchi, leading to difficulty in
breathing.
Lung Cancer: Uncontrolled cell division in the tissues of the lung, often caused by smoking.
5. Important Key Points for Exams
Stomata: Small pores in leaves for gaseous exchange in plants.
Lenticels: Small pores in the bark of woody stems.
6. Gaseous Exchange in Plants (Plants )میں گیسوں کا تبادلہ
, Plants do not have a specialized respiratory system like humans. They exchange gases through
various methods:
Stomata: Most gaseous exchange occurs through stomata in the leaves and young stems.
Lenticels: In woody stems and mature roots, exchange occurs through tiny pores called
lenticels.
Roots: Gas exchange also takes place through the general surface of young roots.
7. Structure of the Lungs ()پھیپھڑوں کی ساخت
The Lungs: Humans have a pair of lungs in the chest cavity. The left lung is slightly smaller
(two lobes) and the right lung is bigger (three lobes).
Pleural Membranes: Each lung is enclosed by two membranes called outer and inner pleural
membranes.
Diaphragm: Below the lungs is a thick muscular structure called the diaphragm.
8. Detailed Comparison: Inhaled vs Exhaled Air.
Feature Inhaled Air (Inside) Exhaled Air (Outside)
Oxygen 21% 16%
Carbon Dioxide 0.04% 4%
Nitrogen 79% 79%
Water Vapours Variable Saturated
9. Frequently Asked Questions (Important for Exams)
Q1: Define Cellular Respiration?
Ans: The process in which C-H bonds in food are broken by oxidation-reduction reactions and
energy is transformed into ATP.
Q2: What is the role of Mucus in the Nose?
Ans: Mucus moistens and warms the air while trapping dust particles.
Q3: What is Nicotine?
Ans: Nicotine is a powerful poison found in cigarettes that damages the central nervous system
and causes addiction
Biology Class 10: Chapter 11
Topic: Homeostasis ()ہومیو سٹیسس
1. Introduction to Homeostasis
Homeostasis is the maintenance of the internal conditions of the body at equilibrium, despite
changes in the external environment.
Example: The human body temperature is maintained at about 37°C.
Key Processes:
Osmoregulation: Maintenance of water and salts in body fluids.
Thermoregulation: Maintenance of internal body temperature.
Excretion: Removal of metabolic wastes from the body.
2. Homeostasis in Plants
Plants also maintain their internal environment using various mechanisms:
