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Unformatted text preview: Biology 240W Notes for Exam #2 Homeostasis I: Osmoregulation-Critical for organisms to balance water and solute concentration to maintain cytoplasm of their cells at optimal state for cellular reactions-many solutes dissolved in body fluids are necessary for organisms to function properly; some are generated as metabolic byproducts and can be harmful to the organism- osmoregulation ( def : process to rid bodies of waste products while maintaining proper amount of water) Diffusion and Osmosis-2 solutions separated by semi-permeable barrier-H20 and solutes will move across until no net movement (equilibrium)-solute movement ( diffusion ) results from this concentration gradient- uncharged solutes: HIGH LOW concentration (water also moves)- osmotic pressure is generated in a solution; it is proportional to osmolarity ( def : combined concentration of all solutes in a solution)- LOW HIGH osmolarity ( osmosis )-solutes also move against concentration gradient (LOW HIGH) in active transport :-requires input of energy-water content is controlled-used to control H20 movement (by osmosis) and solute concentration (by osmoregulation) Osmoregulation in Aquatic Organisms-animals in aquatic environments have large surfaces where solute and water exchange can occur between organism and its environment-separated into 2 groups based on how they balance their osmolarity: 1. Osmoconformers- equilibrate their internal osmolarity to match their external environments-uncommon; only some small marine invertebrates which can tolerate high tissue osmolarity 2. Osmoregulators a. Freshwater-have higher tissue osmolarity than their environments ( hypertonic ) which cause them to take up water by osmosis and lose solutes by diffusion Rid Excess H20 :-Protists forcibly pump H20 out with contractile vacuoles-Large organisms excrete large volumes of very dilute urine; manage salt loss by using active transport pumps to acquire salt from their environment b. Saltwater-body fluids are hypotonic ( have lower osmolarity ) to surroundings and tend to lose water by osmosis and gain salt by diffusion Marine Bony:-to prevent dehydration, consume large volumes of seawater and actively pump salt out of their bodies Marine Cartilaginous:-maintain body fluids at higher osmolarity than surroundings by building up surroundings to metabolic waste products (urea) Osmoregulation in Terrestrial Organisms-most critical challenge to living on land is water conservation (humans die after >10% water loss)-also need to rid metabolic wastes:-primitive form of waste is ammonia which is very toxic so must modify it...
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