PNB 2250 Lecture Notes - Lecture 21: Cnidaria, Extracellular Fluid, Protozoa
10 Nov 2016
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Understand the differences between living in the ocean and on dry land. Terrestrial invertebrates osmoregulators: greatest danger is dehydration. Relevant factors for animal osmoregulation: aquatic vs terrestrial. Permeable or impermeable: blood osmolarity (300-1000 mosm/l, osmoregulatory organs. Impermeable skin: no gills, accelerated water loss through lungs. Cannot be controlled or stopped: to drink water and solutes, to be concerned about desiccation. All cells are hypotonic to seawater: again, desiccation is the main concern. Gills are a site of water and solute movement with the environment. Gills possess aquaporin channels: specifically allow water to move down concentration gradient. Week 8 lecture 21 osmoregulation ii friday 10/21/16: also have solute-specific membrane channels or pumps. Aquatic channels cannot prevent the movement of water or solutes through the gills. Epithelial permeability is a function of the aquatic salinity. Marine invertebrates: seawater and blood have similar osmolarities. Isotonic; not the same solutes: gills rapid solute movement. Highest energy cost: rudimentary kidneys, osmoconformers.
