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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 CO2 to fix carbon (photosynthesis)
– Remove O2 as a byproduct of photosynthesis, and receive O2 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
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