7.1 Specialised Exchange Surfaces

Question 1

Why do some organisms need specialised exchange surfaces ?

Answer 1

Have a higher metabolic rate

High oxygen demands and high carbon dioxide production

Distance between cells were oxygen is needed and the supply of oxygen is too far for effective diffusion

Small SA:V ratio = slow diffusion for amount of gases organism needs to survive

Question 2

Why is diffusion alone sufficient to supply the needs of single celled organisms?

Answer 2

Metabolic rate is low = so O2 demand and CO2 production is low

SA:V is large

Question 3

What makes exchange surfaces efficient ? Give examples of things that have these

Answer 3

Increased surface area - root hair cells

Thin layers : short diffusion distance - alveoli

Good blood supply : maintains steep concentration gradient = fast diffusion - gills / alveoli

Ventilation : maintains steep concentration gradient = more efficient process - gills / alveoli

Question 4

How do you work out the surface area to volume ratio?

Answer 4

Surface area/ volume