1. 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.

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

3. GILLS: External
nudibranch
salamander
larvae

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

5. 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

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

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

8. 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

9. Alveoli are the site of gas exchange with the blood

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

11. oxyhemoglobin
deoxyhemoglobin