HSC Biology — Module 2
Gas Exchange — Flashcards & Quiz
Gas exchange is the movement of respiratory gases — oxygen and carbon dioxide — across a respiratory surface, and HSC Biology Module 2 asks you to compare gas exchange across organisms. The recurring exam framework is the list of features that make a good exchange surface: large surface area, thin walls, moist, close to transport system, maintained concentration gradient. Be ready to apply this to mammalian lungs, fish gills and plant leaves.
Sample Flashcards
Q1: Why do multicellular organisms need specialised gas exchange surfaces?
As organisms increase in size, their surface area to volume (SA:V) ratio decreases. Diffusion alone is too slow to supply O₂ to all cells, so specialised surfaces (lungs, gills) increase the area for gas exchange.
Q2: What are the features of an efficient gas exchange surface?
Large surface area, thin walls (short diffusion distance), moist surface (gases dissolve), rich blood supply (maintains concentration gradient), and ventilation (keeps gradient steep).
Sample Quiz Questions
Q1: As an organism increases in size, its surface area to volume ratio increases.
Answer: FALSE
As size increases, the SA:V ratio DECREASES. This is why larger organisms need specialised gas exchange surfaces — simple diffusion across the body surface becomes insufficient.
Q2: Efficient gas exchange surfaces are thin, moist, and have a large surface area.
Answer: TRUE
These features maximise the rate of diffusion: thin walls shorten diffusion distance, moisture dissolves gases, and large SA allows more gas exchange simultaneously.
Related Concepts
Last updated: March 2026 · 2 flashcards · 2 quiz questions