7.1 Specialised Exchange Surfaces

Question 1

Why can diffusion alone be enough to supply the needs of single celled organisms

Answer 1

Low metabolic activity so o2 demands and co2 production is low
Surface area to volume ratio is large

Question 2

Why is it harder for larger animals to deliver substances to cells due to their surface area to volume ratio

Answer 2

The bigger the organism the smaller the surface area to volume ration becomes and this means the distrance the substances need to travel from the outside to reach cells at the centre of the body get longer

Question 3

What are the common features in effective specialised exchange surfaces in large multicellular organisms

Answer 3

Increase surface area
Thin layers
Good blood supply - Steeper conc gradient
Ventilation to maintain diffusion gradient