Igcse Model Questions Vol1 2025 Biology Question 4

Practice essay / theory question 4 from the 2025 Igcse Model Questions Vol1 Biology examination. This question covers human respiration .

Igcse Model Questions Vol1 2025 Biology Essay / Theory
Topic: human respiration
Question 4 IGCSE_MODEL_QUESTIONS_VOL1 • 2025 • BIOLOGY • essay

The diagram shows the major structures of the human respiratory system.

Question Parts

( a )
Describe, in the correct order, the complete pathway that air follows from the external environment to the site where gas exchange occurs. Name each structure the air passes through.
( b )
Explain the roles of the diaphragm and the external intercostal muscles during (i) inhalation and (ii) exhalation, and state how their actions affect the volume of the thoracic cavity.
( c )
The partial pressure of oxygen (pO₂) in alveolar air is 0.16 atm and in the blood of the pulmonary capillaries it is 0.13 atm. Using these values, explain why oxygen diffuses from the alveoli into the blood, referring to the principles of diffusion.
( d )
A swimmer at sea level (atmospheric pressure 1.0 atm) takes a deep breath and holds it for 5 seconds before diving. Discuss two physiological advantages of this breath‑holding technique for the swimmer.

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About This Question

This is Igcse Model Questions Vol1 2025 Biology Question 4. It is one of the essay questions from the 2025 Igcse Model Questions Vol1 Biology examination.

The question covers human respiration .

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