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campbell44hand - Osmoregulation and The Kidney...

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Osmoregulation and The Kidney Physiological systems of animals operate in a fluid environment Relative concentrations of water and solutes must be maintained within fairly narrow limits Osmoregulation regulates solute concentrations and balances the gain and loss of water Freshwater animals show adaptations that reduce water uptake and conserve solutes Desert and marine animals face desiccating environments that can quickly deplete body water Excretion gets rid of nitrogenous metabolites and other waste products Osmosis and Osmolarity Osmolarity , the solute concentration of a solution, determines the movement of water across a selectively permeable membrane If two solutions are isoosmotic , the movement of water is equal in both directions If two solutions differ in osmolarity, the net flow of water is from the hypoosmotic to the hyperosmotic solution Osmoconformers , consisting only of some marine animals, are isoosmotic with their surroundings and do not regulate their osmolarity All are marine animals Osmoregulators expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment Can tolerate freshwater and land environments Can allow marine animals to have different osmolarity compared to seawater Most animals are stenohaline ; they cannot tolerate substantial changes in external osmolarity Euryhaline animals can survive large fluctuations in external osmolarity (e.g. Salmon) Marine Animals Most marine invertebrates are osmoconformers Most marine vertebrates and some invertebrates are osmoregulators Marine bony fishes are hypoosmotic to sea water They lose water by osmosis and gain salt by diffusion and from food They balance water loss by drinking seawater and excreting salts Marine bony fishes are hypoosmotic to sea water Gills and kidneys pump out excess salt and other ions with very little water loss
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Freshwater animals Freshwater animals constantly take in water by osmosis from their hypoosmotic environment They lose salts by diffusion and maintain water balance by excreting large amounts of dilute urine Salts lost by diffusion are replaced in foods and by uptake across the gills Freshwater animals constantly take in water by osmosis from their hypoosmotic environment Cells in gills actively transport salt into fish Animals That Live in Temporary Waters Some aquatic invertebrates in temporary ponds lose almost all their body water and survive in a dormant state This adaptation is called anhydrobiosis Land Animals Land animals manage water budgets by drinking and eating moist foods and using metabolic water Skins are used to minimize water loss Behaviors also used to minimize water loss Desert animals get major water savings from simple anatomical features and behaviors such as a nocturnal life style Kangaroo rat loses little water Requires little water ingestion and loses most from evaporation Transport Epithelia in Osmoregulation
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campbell44hand - Osmoregulation and The Kidney...

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