Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Osmoregulation regulates solute concentrationsand balances the gain and loss of water• Excretion gets rid of metabolic wastesLE 7-12Lowerconcentrationof solute (sugar)Higherconcentrationof sugarSame concentrationof sugarSelectivelypermeable mem-brane: sugar mole-cules cannot passthrough pores, butwater molecules canH2OOsmosisLE 7-13AnimalcellLysedH2OH2OH2ONormalHypotonic solutionIsotonic solution Hypertonic solutionH2OShriveledH2OH2OH2OH2OPlantcellTurgid (normal)Flaccid PlasmolyzedCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsOsmotic Challenges• Osmoconformers, consisting only of some marineanimals, are isoosmotic with their surroundingsand do not regulate their osmolarity• Osmoregulators expend energy to control wateruptake and loss in a hyperosmotic or hypoosmoticenvironmentCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Most animals are stenohaline; they cannot toleratesubstantial changes in external osmolarity• Euryhaline animals can survive large fluctuationsin external osmolarityCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsMarine Animals• Most marine invertebrates are osmoconformers• Most marine vertebrates and some invertebratesare osmoregulatorsLE 44-3aGain of water andsalt ions from foodand by drinkingseawaterOsmotic water lossthrough gills and other partsof body surfaceExcretion ofsalt ionsfrom gillsOsmoregulation in a saltwater fishExcretion of salt ions and small amountsof water in scantyurine from kidneysLE 7-17DiffusionFacilitated diffusionPassive transportATPActive transportLE 44-3bExcretion oflarge amounts ofwater in diluteurine from kidneysOsmotic water gainthrough gills and other partsof body surfaceOsmoregulation in a freshwater fishUptake ofsalt ionsby gillsUptake ofwater and someions in foodLE 44-5Waterbalance in a kangaroo rat(2 mL/day)Waterbalance ina human(2,500 mL/day)WatergainWaterlossDerived frommetabolism (1.8 mL)Ingestedin food (0.2 mL)Derived frommetabolism (250 mL)Ingestedin food (750 mL)Ingestedin liquid (1,500 mL)Evaporation (900 mL)Feces (100 mL)Urine(1,500 mL)Evaporation (1.46 mL)Feces (0.09 mL)Urine(0.45 mL)Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsA freshwater fish is going to need to• A. drink water and excrete excess salts from itsbody• B. drink water and take up salts from thesurrounding water• C. excrete excess water and excess salts• D. excrete excess water and take up salts from thesurrounding water• E. change its osmoregulatory strategy dependingon outside conditionsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsTransport Epithelia• Transport epithelia are specialized cells thatregulate solute movement• They are essential components of osmoticregulation and metabolic waste disposal• They are arranged in complex tubular networks• An example is in salt glands of marine birds, whichremove excess sodium chloride from the bloodLE 44-7aNostrilwith saltsecretionsNasal salt glandLE 44-7bVeinCapillarySecretorytubuleTransportepitheliumDirectionof saltmovementCentralductArteryBloodflowLumen ofsecretory tubuleNaClSecretory cellof transportepitheliumCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 44.2: An animal’s nitrogenous wastesreflect its phylogeny and habitat• The type and quantity of an animal’s wasteproducts may greatly affect its water balance• Among the most important wastes are nitrogenousbreakdown products of proteins and nucleic acidsLE 44-8Nitrogenous basesNucleic acidsAmino acidsProteins—NH2Amino groupsMost aquaticanimals,including mostbony fishesMammals, mostamphibians,sharks, some bonyfishesMany reptiles(includingbirds), insects,land snailsAmmonia Urea Uric
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