Diffusion
The passive movement of molecules or particles along a concentration gradient, or from regions of higher to regions of lower concentration.
Fick's Law
surface area x difference in concentration / length of diffusion path
what does amoeba use as a respiratory surface
it's cell membrane
how has flatworm achieved a large enough SA:V to meet its requirements for gas exchange
by having a flattened body meaning no part of the body is far from the surface so the diffusion pathway is short
Why do larger organisms need a specialised exchange surface?
the have a smaller SA:V than smaller organisms of simillar shape so diffusion across their surface is not efficient enough to meet their needs
3 features required for efficient gas exchange
short diffusion pathway, permeable , maintained concentration gradient
why do larger complex animals need a ventilation mechanism
maintains steep concentration gradient across respiratory surfaces
direction of blood and water flow trough the gills of bony fish term?
counter current flow - blood and water flow in opposite directions to each other
why more difficult to carry out gas exchange in water
20x more o2 in air then water diffusion if gas molecules more rapid in airair is less viscous than water ventilation in air requires less energy than in water