7.1 Specialised exchange surfaces

Question 1

Why is diffusion alone not enough to supply the needs of a single-celled organism? (2 reasons)

Answer 1

-metabolic activity of a single-celled organism is usually low, so O2 and C02 production of cell is relatively low
-SA:V ratio of organisms is large

Question 2

Features of effective exchange surfaces:

Answer 2

-increased surface area
-thin layers (short diffusion distance)
-good blood supply (steeper conc gradient (substances constantly delivered to and removed from)= faster diffusion)
-ventilation to maintain diffusion gradient