GAS EXCHANGE in ANIMALS aka respiration • Respiration involves the diffusion of O2/CO2 across membranes • CM requires water to be stable (no bonds between phospholipids) I had to delete some graphics to keep this under 5mb, sorry • Therefore, respiratory surfaces are wet : gills, lungs, skin, etc.

FICK’S LAW: Rate (R) of diffusion determined by: Concentration gradient Surface area Distance of diffusion

GILLS: External nudibranch salamander larvae

GILLS: Internal In osteichthyes, covered by the operculum Not so in chondrichthyes

Counter-current flow of blood/water maximizes diffusion Water must flow across gills continuously, via swimming, or pumping of operculum water blood Counter-current flow of blood/water maximizes diffusion

On land, respiratory structures need support & protection from drying out Spiracle/tracheal system of Arthropoda

LUNGS employ smaller and smaller tubes Reduces water loss from surface Gases move in/out based on differences in air pressure

Amphibians create high pressure in buccal cavity, forcing air into lungs More common is the opposite – low (negative) pressure in lung cavity causes air to rush in ribcage raised, diaphragm drops, volume increases, pressure decreases

Alveoli are the site of gas exchange with the blood

GAS TRANSPORT O2 has low solubility (3mL/L) Solution? Bind it to Fe-containing hemoglobin in RBC (200mL/L)

oxyhemoglobin deoxyhemoglobin