7.1 - Specialised Exchange Surfaces

Question 1

Why is diffusion enough to supply unicellular organism?

Answer 1

• Low metabolic activity, O2 requirement and CO2 production is low
• Large SA:V ratio - gases exchanged fast enough

Question 2

Describe 3 characteristics of specialised exchange surfaces.

Answer 2

Increased SA: Provides large enough are to increase exchange and overcome limits of low SA:V ratio of large multicellular organisms (e.g. root hairs, villi)

Thin Layers: Diffuse distance decreased, increasing rate.

Good blood supply: Good blood supply increases conc. gradient, of gases in mammals.
E.g. fish gills, lung alveoli