10th Class Biology Chapter 10 Notes | Get Now
10th Class Biology Chapter 10 Notes cover an essential topic from the Matric Biology syllabus — Gaseous Exchange. This chapter explains how plants and humans exchange oxygen and carbon dioxide, how the human respiratory system works, and how smoking and diseases affect the lungs. These 10th Class Biology Chapter 10 Notes are designed to simplify every definition, process, and diagram so students can revise quickly before exams.
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Gaseous exchange is a fundamental life process, and this chapter connects biology concepts with real-life health issues like bronchitis, asthma, and lung cancer. These 10th Class Biology Chapter 10 Notes break the chapter into easy sections covering plants, the human respiratory system, breathing mechanism, and respiratory diseases.
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What This Chapter Covers
Chapter 10 of 10th Class Biology, titled “Gaseous Exchange,” explains:
- Cellular respiration and breathing
- Gaseous exchange in plants
- The human respiratory system
- Mechanism of breathing
- Comparison of inspired and expired air
- Respiratory disorders: bronchitis, emphysema, pneumonia, asthma, and lung cancer
- Effects of smoking on the body
Cellular Respiration and Breathing
Before understanding gaseous exchange, students must know the difference between cellular respiration and breathing, as this is a commonly asked exam question.
Cellular Respiration
Cellular respiration is the process in which carbon-hydrogen bonds in food are broken by oxidation-reduction reactions, releasing energy that is converted into ATP (Adenosine Triphosphate).
Breathing
Breathing is the physical process through which animals take in air to get oxygen and release carbon dioxide. Unlike respiration, breathing is purely a mechanical process and does not produce energy.
Key Difference
| Feature | Breathing | Cellular Respiration |
|---|---|---|
| Level | Organ system level | Cell level |
| Energy | No energy produced | ATP is produced |
| Nature | Mechanical process | Biochemical process |
Gaseous Exchange in Plants
According to these 10th Class Biology Chapter 10 Notes, plants do not have specialized organs for gaseous exchange. Instead, every cell exchanges gases independently through different structures.
Methods of Gaseous Exchange in Plants
- Through Cuticle: In young stems and leaves, some gas exchange occurs through the cuticle covering the epidermis.
- Through Stomata: Leaves and young stems exchange gases through stomata present in their epidermis.
- Through Air Spaces: Mesophyll cells inside leaves have air spaces that help gases move within the leaf.
- Through Lenticels: In woody stems and mature roots, small pores called lenticels allow gas exchange through the bark.
- Through Roots: Gases diffuse in and out through the general surface of young roots.
- In Aquatic Plants: Aquatic plants absorb oxygen dissolved in water and release carbon dioxide directly into the water.
During the day, oxygen produced in photosynthesis is used in cellular respiration, and the carbon dioxide from respiration is reused in photosynthesis. At night, since photosynthesis stops, leaf cells absorb oxygen from the environment.
The Human Respiratory System
The human respiratory system has two main parts: the air passageway and the lungs. This section of the 10th Class Biology Chapter 10 Notes is one of the most important for diagram-based exam questions.
The Air Passageway
Air travels through the following parts in order:
- Nostrils
- Nasal cavity
- Internal nostrils
- Pharynx
- Larynx
- Trachea
- Bronchi
- Bronchioles
- Alveolar ducts
- Alveoli
Key Structures Explained
Nasal Cavity: Lined with fine hairs and mucus that filter dust particles, moisten air, and warm it to body temperature.
Pharynx: A muscular passage common to both food and air.
Larynx: Also called the voice box. It contains the glottis (a narrow opening) guarded by the epiglottis, and vocal cords that vibrate to produce sound.
Trachea: Known as the windpipe, about 12 cm long, supported by C-shaped cartilaginous rings that prevent it from collapsing.
Bronchi and Bronchioles: The trachea divides into two bronchi, which further divide into smaller bronchioles inside the lungs.
Alveoli: Tiny sac-like structures where actual gaseous exchange takes place. They are surrounded by a network of capillaries.
The Lungs
- Humans have a pair of lungs in the thoracic cavity
- The right lung has three lobes; the left lung has two lobes
- Lungs are protected by the outer and inner pleural membranes, which contain fluid for lubrication
- A muscular diaphragm lies below the lungs
Mechanism of Breathing
Breathing has two phases: inhalation and exhalation. This is a frequently tested long question in board exams.
Inhalation (Inspiration)
During inhalation, the rib muscles contract and ribs rise, while the diaphragm contracts and moves down. This increases the thoracic cavity’s volume, reducing pressure inside the lungs so air rushes in.
Exhalation (Expiration)
During exhalation, the rib muscles relax, the diaphragm relaxes and moves up, reducing the thoracic cavity’s space. This increases pressure on the lungs, pushing air out.
Breathing Rate
- Normal breathing rate: 16-20 times per minute at rest
- During exercise, breathing rate can rise to 30-40 times per minute
- Breathing is controlled by the respiratory centre in the brain, which responds to carbon dioxide levels in the blood
Comparison of Inspired and Expired Air
This table is a common short-question topic in the 10th Class Biology Chapter 10 Notes:
| Feature | Inspired Air | Expired Air |
|---|---|---|
| Oxygen | 21% | 16% |
| Carbon dioxide | 0.04% | 4% |
| Nitrogen | 79% | 79% |
| Water vapours | Variable | Saturated |
| Temperature | Variable | Almost equal to body temperature |
Respiratory Disorders
This chapter covers five major respiratory diseases, each commonly asked as a long question in exams.
Bronchitis
Bronchitis is the inflammation of the bronchi or bronchioles, caused by viruses, bacteria, or chemical irritants like tobacco smoke. It has two types:
- Acute bronchitis – lasts about two weeks with no permanent damage
- Chronic bronchitis – lasts three months to two years, common in people 45 or older
Emphysema
Emphysema is the destruction of alveolar walls, leading to larger air sacs with reduced surface area for gaseous exchange. Symptoms often appear only after 50-70% of lung tissue is already damaged.
Pneumonia
Pneumonia is an infection of the lungs, most commonly caused by the bacterium Streptococcus pneumoniae. When both lungs are affected, it is called double pneumonia. Symptoms include fever, cough, and shortness of breath.
Asthma
Asthma is a form of allergy where allergens like dust, smoke, or pollen cause the bronchi to become inflamed and narrow. Inhalers containing bronchodilators are used for treatment.
Lung Cancer
Lung cancer involves uncontrolled cell division in lung tissue, mainly caused by smoking. It is responsible for more than 1.3 million deaths worldwide every year.
Effects of Smoking on the Body
Smoking is a major focus of this chapter because of its direct link to respiratory diseases. Key facts include:
- Cigarette smoke contains over 4,000 chemicals, at least 50 of which are carcinogens
- Smoking increases tuberculosis risk by two to four times and pneumonia risk by four times
- Nicotine hardens artery walls and damages brain tissue
- Passive smokers face a 25-30% higher risk of heart disease and 20-30% higher risk of lung cancer
- Smoking rates are declining in developed countries but rising by 3.4% yearly in developing nations
For more chapter-wise resources, visit [internal link] to explore complete 10th Class Biology notes on TaleemWorld.com.
Why These Notes Matter for Exam Preparation
These 10th Class Biology Chapter 10 Notes are arranged to match the board exam format, covering MCQs, short questions, and long questions in one place. Diagrams like the air passageway, alveoli, and breathing mechanism are especially important since they appear frequently in practical and theory exams.
Students should focus on comparison tables (breathing vs respiration, inspired vs expired air) since these are high-scoring, easy-to-remember questions.
FAQs
Q1. What topics are included in 10th Class Biology Chapter 10 Notes?
These notes cover gaseous exchange in plants, the human respiratory system, breathing mechanism, comparison of inspired and expired air, and respiratory diseases like bronchitis, asthma, pneumonia, and lung cancer.
Q2. What is the difference between breathing and cellular respiration?
Breathing is a mechanical process of taking in oxygen and releasing carbon dioxide, occurring at the organ level. Cellular respiration is a biochemical process at the cell level that produces energy in the form of ATP.
Q3. How do plants exchange gases without lungs?
Plants exchange gases through stomata in leaves, cuticle on young stems, lenticels in woody stems, and the general surface of roots. Aquatic plants absorb dissolved oxygen directly from water.
Q4. What happens during inhalation and exhalation?
During inhalation, rib muscles contract and the diaphragm moves down, letting air rush in. During exhalation, these muscles relax, reducing lung space and pushing air out.
Q5. Which disease destroys the walls of alveoli?
Emphysema destroys the walls of the alveoli, creating larger air sacs with less surface area for gas exchange. This makes breathing difficult and often develops after long-term smoking or exposure to pollutants.
Q6. How does smoking affect the respiratory system?
Smoking damages the air passageway with over 4,000 chemicals, increasing risks of bronchitis, emphysema, pneumonia, and lung cancer. It also hardens arteries and reduces the blood’s oxygen-carrying capacity.