Igcse Model Questions Vol1 2025 Biology Question 29

Practice objective / multiple choice question 29 from the 2025 Igcse Model Questions Vol1 Biology examination.

Igcse Model Questions Vol1 2025 Biology Objective / Multiple Choice Medium Difficulty
Question 29 IGCSE_MODEL_QUESTIONS_VOL1 • 2025 • BIOLOGY • objective

During a fever, the human body employs vasodilation and sweating to dissipate heat. Experimental data show that for each degree Celsius rise in core temperature above the normal 37 °C, skin blood flow increases by 30 % and the sweating rate increases by \(0.5\) mL min\(^{-1}\). If a patient's core temperature rises to 39 °C, (a) calculate the percentage increase in skin blood flow and the increase in sweating rate. (b) Assuming each 1 % increase in skin blood flow removes \(0.02\) W of heat and each millilitre of sweat evaporated removes \(0.24\) W, determine which mechanism contributes more to heat loss at this temperature.

Answer Options

A. Skin blood flow increases by 90 % and sweating by 1.5 mL min\(^{-1}\). Heat loss: vasodilation ≈ 1.8 W, sweating ≈ 0.36 W; vasodilation contributes more.
B. Skin blood flow increases by 60 % and sweating by 0.5 mL min\(^{-1}\). Heat loss: vasodilation ≈ 1.2 W, sweating ≈ 0.12 W; vasodilation contributes more.
C. Skin blood flow increases by 30 % and sweating by 1.0 mL min\(^{-1}\). Heat loss: vasodilation ≈ 0.6 W, sweating ≈ 0.24 W; sweating contributes more.
Correct Answer D. Skin blood flow increases by 60 % and sweating by 1.0 mL min\(^{-1}\). Heat loss: vasodilation ≈ 1.2 W, sweating ≈ 0.24 W; vasodilation contributes more.
Correct Answer
D
Correct Option:
Skin blood flow increases by 60 % and sweating by 1.0 mL min\(^{-1}\). Heat loss: vasodilation ≈ 1.2 W, sweating ≈ 0.24 W; vasodilation contributes more.

About This Question

This is Igcse Model Questions Vol1 2025 Biology Question 29. It is one of the objective questions from the 2025 Igcse Model Questions Vol1 Biology examination.

Difficulty level: Medium .

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