PNB 2250 Lecture Notes - Lecture 4: Ion Exchange
8 Sep 2016
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Requires animal to maintain internal water levels: advantages: Terrestrial animals: surface area/volume of most terrestrial animals is less than 3, shape is not due to a consideration of external gas diffusion. Types of respiratory organs: evaginations (turned out) gills. Hydrodynamics- water flow and resistance are important to consider: invaginations (turned in) lungs. Very little structural integrity outside of water due to buoyancy requirement. Must always be swimming: water moves past gills as a result of movement. More energetically efficient than pumping water past gills. Low friction surface present to allow this: water moves over gills while animal swims, ciliary action increases diffusion efficiency. Water and ions moving past: overcoming limits of diffusion, osmotic regulation. Getting rid of solutes if necessary: food uptake. Small food bits can be taken up in gills. Aqueous vertebrates: gill slits, ram ventilation, excretion of solutes, movement of water. Very thin, large surface area: densely packed.
