gas exchange in animals

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