Gaseous exchange systems Biology 2: Form and Function

Gaseous exchange in animals Respiratory surfaces must be kept moist and maximize surface area Small, aquatic animals may use direct diffusion Medium aquatic animals use gills –All exchange systems (gases, heat, wastes) use counter-current mechanism –Larger aquatic animals use ventilation Terrestrial animals internalized respiratory surface (lungs)

Lower blood pH and higher blood temperatures facilitate oxygen unloading

Gaseous exchange in plants Plants must: –Receive CO 2 to fix carbon (photosynthesis) –Remove O 2 as a byproduct of photosynthesis, and receive O 2 for respiration So that plants can control gaseous exchange, it only occurs at particular pores called stomata that regulate flow Stomata also play a key role in controlling transpiration

Stomata - the movie