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Syllabus

Breathing and Exchange of Gases — Syllabus

ICSE · Class 11 · Biology

What Breathing and Exchange of Gases covers in ICSE Class 11 Biology: 4 topics, for the 2026-27 session. Part of the ICSE Class 11 Biology syllabus.

60 questions40 flashcards4 formulas & key relations5 concepts

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An infographic comparing different types of respiratory organs found in various animals, such as moist cuticle (earthworm), gills (fish, aquatic arthropods, molluscs), tracheal tubes (insects), and lu
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4 Topics · ICSE Class 11 Biology · 2026-27

Topics in Breathing and Exchange of Gases

1

1. Respiratory organs in animals

  • Respiratory organs are the organs concerned with gaseous exchange, that is, intake of oxygen and output of carbon dioxide.
  • In unicellular organisms such as Amoeba, gaseous exchange occurs through the general body surface or plasmalemma.
  • In Sycon and Hydra, gas exchange takes place by simple diffusion between flowing water and individual cells.
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2. Human respiratory system

  • The human respiratory system has two main components: the lungs and the respiratory tract.
  • The respiratory tract includes nostrils, nasal cavity, nasopharynx, larynx, trachea, bronchi, and bronchioles.
  • Nostrils are the openings of the nasal cavities.
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3. Mechanism of breathing and gas exchange

  • Breathing is the mechanical process of taking fresh air into the lungs and expelling foul air from the lungs.
  • Inspiration is active and expiration is passive.
  • Breathing is involuntary and normally occurs at a constant rate of 12 to 14 per minute in a resting person.
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4. Transport of oxygen and carbon dioxide

  • About 97 per cent of oxygen is transported by RBCs and about 3 per cent is carried dissolved in plasma.
  • In arterial blood, about 19 mL of oxygen is present per 100 mL blood; 0.3 mL is dissolved in plasma and 18.7 mL is bound to haemoglobin.
  • Haemoglobin is an iron-containing respiratory pigment in RBCs.

Key Concepts

Central concept: Respiration and gaseous exchange in animals and humans

RespirationRespiratory organsRespiratory system in humansMechanism of breathingGas exchangeTransport of gasesRegulation of respirationRespiratory volumes and capacities

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Frequently Asked Questions

What are the important topics in Breathing and Exchange of Gases for ICSE Class 11 Biology?
Key topics in Breathing and Exchange of Gases include Respiratory organs in animals, Human respiratory system, Mechanism of breathing and gas exchange, Transport of oxygen and carbon dioxide. Study these first, then practise questions on each for Class 11 exams.
How should I revise Breathing and Exchange of Gases for Class 11 exams?
Learn the core ideas first, then work through the 60 practice questions on Breathing and Exchange of Gases. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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All ICSE Class 11 Biology Syllabus

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