Regulating The Internal Environment Homeostasis The ability of animals to regulate their internal environment. The ability of animals to regulate their.

Regulating The Internal Regulating The Internal EnvironmentEnvironment

HomeostasisHomeostasis

The ability of animals to regulate their The ability of animals to regulate their internal environment.internal environment. ThermoregulationThermoregulation -- the ability of animals the ability of animals

to regulate their internal temperature.to regulate their internal temperature. OsmoregulationOsmoregulation – the ability of animals to– the ability of animals to

regulate their water balance.regulate their water balance. ExcretionExcretion – how animal s rid themselves of – how animal s rid themselves of

nitrogenous wastes.nitrogenous wastes.

An Overview of HomeostasisAn Overview of Homeostasis

RegulatorsRegulators - actively regulate their own - actively regulate their own internal environment in response to external.internal environment in response to external. Cannot tolerate large internal changes.Cannot tolerate large internal changes. Salmon are osmoregulatorsSalmon are osmoregulators Endotherms are thermoregulatorsEndotherms are thermoregulators

Conformers Conformers – allow some conditions to vary – allow some conditions to vary in response to the external environment.in response to the external environment. Live in relatively stable environments and Live in relatively stable environments and

somewhat conform to their external environment.somewhat conform to their external environment. Spider crabs will gain or lose water in reponse to a Spider crabs will gain or lose water in reponse to a

variation in salinity.variation in salinity.

Regulaters Verses Conformers

No Organism is a Perfect No Organism is a Perfect Conformer or RegulatorConformer or Regulator

Salmon may osmoregulate but they Salmon may osmoregulate but they generally conform to the external generally conform to the external temperatures.temperatures.

For a particular condition animals may For a particular condition animals may regulate or conform.regulate or conform. A forest dwelling lizard may have to travel long A forest dwelling lizard may have to travel long

distances to perch in the sun and therefore distances to perch in the sun and therefore choose to regulate its body temperature in the choose to regulate its body temperature in the forest to avoid predation. The same lizard may forest to avoid predation. The same lizard may choose to bask in the sun in open predation.choose to bask in the sun in open predation.

Biochemical and Physiological Biochemical and Physiological Processes Vary With Body Processes Vary With Body

Temperature.Temperature. Enzyme mediated reactions may vary 2-3 fold for Enzyme mediated reactions may vary 2-3 fold for

every 10every 10oo C temperature increase. C temperature increase. QQ10 10 effecteffect – multiple by which a particular process – multiple by which a particular process

increases with a 10increases with a 10oo increase in body temperature. increase in body temperature. Glycogen hydrolysis occurs 2.5 greater at 30Glycogen hydrolysis occurs 2.5 greater at 30ooC than 20C than 20ooC C

then the Qthen the Q1010 of the reaction is 2.5. of the reaction is 2.5. Membranes are affected by temperature and can Membranes are affected by temperature and can

affect animal unction.affect animal unction. Muscle contractions can be affected and the ability of Muscle contractions can be affected and the ability of

the animal to run, jump or fly.the animal to run, jump or fly. All animals have an optimal temperature in which All animals have an optimal temperature in which

they can function.they can function.

Physical Processes Account for Physical Processes Account for Heat Lost or Gained.Heat Lost or Gained.

Conduction Conduction - Direct transfer of heat through - Direct transfer of heat through contact with the environment.contact with the environment.

ConvectionConvection - transfer of heat by the - transfer of heat by the movement of a liquid or gas past a movement of a liquid or gas past a surface.surface.

RadiationRadiation - emission of electromagnetic - emission of electromagnetic radiation from objects.radiation from objects.

EvaporationEvaporation – heat removal through – heat removal through evaporationevaporation

Heat ExchangeHeat Exchange

Cool Purple Lizard on a RockCool Purple Lizard on a Rock

Ectothermy Verses Ectothermy Verses EndothermyEndothermy

EctothermsEctotherms generate such little heat through metabolism generate such little heat through metabolism that their body temperature is determined by the that their body temperature is determined by the environment.environment.

Because Because endothermsendotherms can maintain a stable internal can maintain a stable internal temperature they can sustain prolonged activities.temperature they can sustain prolonged activities.

EndothermsEndotherms are also better designed to live on land and are also better designed to live on land and can tolerate the large fluxuations in temperature.can tolerate the large fluxuations in temperature.

A disadvantage of being an A disadvantage of being an endothermendotherm is that they must is that they must consume much more food because of their energy needs. consume much more food because of their energy needs.

Endotherms Verses Ectotherms

Physiological Physiological ThermoregulationThermoregulation

Adjusting the rate of heat exchange Adjusting the rate of heat exchange between the organism and its between the organism and its environment.environment. InsulationInsulation – fur and feather fluffing – fur and feather fluffing VasodilationVasodilation – dilate blood vessels at – dilate blood vessels at

the surface of the skin to dissapate heat.the surface of the skin to dissapate heat. VasoconstrictionVasoconstriction – constrict blood – constrict blood

vessels to direct blood towards the core vessels to direct blood towards the core and away from the extremities where and away from the extremities where heat is lost.heat is lost.

Countercurrent Heat Countercurrent Heat ExchangeExchange

Arrangement of blood vessels are designed to Arrangement of blood vessels are designed to either trap or release heat more efficiently.either trap or release heat more efficiently.

Arteries carrying warm blood from the Arteries carrying warm blood from the animal’s core are in close proximity to the animal’s core are in close proximity to the cooler blood in the veins returning to the core.cooler blood in the veins returning to the core.

Keeps artic wolf legs from freezing.Keeps artic wolf legs from freezing. By counter current exchange un-insulated toe pads are By counter current exchange un-insulated toe pads are

kept just above 0 kept just above 0 o o C to prevent heat loss but not cold C to prevent heat loss but not cold enough to freeze.enough to freeze.

Help dissipate heat when running long distances.Help dissipate heat when running long distances.

Counter Current Heat Exchange

Puffin

Warm Blood Heats Cold Blood

Great White Shark

Thermoregulation of the Shark

Skin Section

Evaporative CoolingEvaporative Cooling SweatingSweating PantingPanting Making their bodies wetMaking their bodies wet

BehavioralBehavioral Change postureChange posture MigrateMigrate Bask in the sun or go swimmingBask in the sun or go swimming

Changing the rate of metabolic heat Changing the rate of metabolic heat productionproduction Non-shivering thermogenesisNon-shivering thermogenesis

Brown fatBrown fat – lipid found in the neck and shoulders of – lipid found in the neck and shoulders of some animals that create mostly thermal energysome animals that create mostly thermal energy

Happy Happy Hippos

InvertebratesInvertebrates

Mostly thermoconformersMostly thermoconformers Desert locusts don’t move until they warm Desert locusts don’t move until they warm

up.up. Some bees and moths are endothermicSome bees and moths are endothermic

Flight muscles generate heatFlight muscles generate heat Some shiver to produce heatSome shiver to produce heat Countercurrent exchangeCountercurrent exchange

Some bees huddle together when coldSome bees huddle together when cold Some bees transport water to the hive and Some bees transport water to the hive and

evaporate the water by fanning their wings.evaporate the water by fanning their wings.

Adjustment to Changing Adjustment to Changing TemperaturesTemperatures

Nerves in the skin sense temperature changes Nerves in the skin sense temperature changes and the and the hypothalamushypothalamus in the brain responds. in the brain responds.

AcclimmatizationAcclimmatization is a physiological response is a physiological response to temperature change over a period of weeks to temperature change over a period of weeks or days.or days. Grow a thicker coat or shed.Grow a thicker coat or shed. Produce enzymes that work at different Produce enzymes that work at different

temperatures.temperatures. Membranes change proportion of saturated verses Membranes change proportion of saturated verses

unsaturated fatty acids within the phospholipds.unsaturated fatty acids within the phospholipds. May creates May creates cryoprotectantcryoprotectant compounds. compounds.

Cells can make rapid adjustments in Cells can make rapid adjustments in response to extreme stress.response to extreme stress. Heat shock proteinsHeat shock proteins – help maintain – help maintain

the integrity of other proteins that would the integrity of other proteins that would denature under extreme heat.denature under extreme heat.

The physiological adaptations that The physiological adaptations that animals make during acclimatization animals make during acclimatization affect their tolerance to temperature.affect their tolerance to temperature. Summer acclimatization of the bull Summer acclimatization of the bull

heaeded cat fish can survive water heaeded cat fish can survive water temperatures of 36temperatures of 36ooC but cannot C but cannot function in cold water.function in cold water.

How Animals Deal With How Animals Deal With Environmental ExtremesEnvironmental Extremes

TorporTorpor is a physiological state in which is a physiological state in which activity is low and metabolism decreases.activity is low and metabolism decreases.

HibernationHibernation is a long term winter torpor.is a long term winter torpor. EstivationEstivation is a long term summer torpor is a long term summer torpor

when sources of water are scarce.when sources of water are scarce. Daily Torpor Daily Torpor is a short term torperis a short term torper

Adpated to feeding patterns.Adpated to feeding patterns. Shrews feed at night and are inactive during the Shrews feed at night and are inactive during the

day.day. Appears to be controlled by a biological clock.Appears to be controlled by a biological clock.

The Belding’s squirrel can live on The Belding’s squirrel can live on one Kcal per day while hibernatingone Kcal per day while hibernating

Water and Water and Waste DisposalWaste Disposal

OsmoregulationOsmoregulation

Management of the body’s solute Management of the body’s solute concentration.concentration.

Management of water into and out of Management of water into and out of the body.the body.

Depends on Depends on transport epitheilium.transport epitheilium. Layer or layers of specialized cells that Layer or layers of specialized cells that

regulate solute movements in a particular regulate solute movements in a particular direction and in certain quantities.direction and in certain quantities.

Structure Verses FunctionStructure Verses Function

Some of these epitheilia Some of these epitheilia Face outwardsFace outwards Line openingsLine openings Are arranged in tubular networks that Are arranged in tubular networks that

have large surface areas.have large surface areas. Joined by tight junctions to create Joined by tight junctions to create

barriers between the environment and barriers between the environment and body tissuebody tissue

Salt Excreting glands in Birds

The Nature of Nitrogenous The Nature of Nitrogenous Waste Waste

Nitrogenous wastes are created through Nitrogenous wastes are created through de-amination, the removal of an amine de-amination, the removal of an amine group from of proteins and nucleic acids.group from of proteins and nucleic acids.

Primary toxic product is ammonia.Primary toxic product is ammonia.

These wastes must be dissolved in water These wastes must be dissolved in water and therefore affect the water balance.and therefore affect the water balance.

Nitrogenous Waste Depends on Nitrogenous Waste Depends on HabitatHabitat

The kinds of nitrogenous waste an animal The kinds of nitrogenous waste an animal excretes depends on the availability of water in excretes depends on the availability of water in its habitat and evolutionary history.its habitat and evolutionary history.

The amount and composition of waste produced The amount and composition of waste produced depends on energy needs and diet.depends on energy needs and diet.

Endotherms have high energy needs and consequently Endotherms have high energy needs and consequently excrete more than ectotherms.excrete more than ectotherms.

Carnivores take in large amounts of protein and excrete Carnivores take in large amounts of protein and excrete large amounts of nitorgenous watse.large amounts of nitorgenous watse.

AmmoniaAmmonia

Animals that live in the water can excrete Animals that live in the water can excrete ammonia.ammonia.

They can simply swim away from their waste.They can simply swim away from their waste.

Requires less energy to convert ammonia to Requires less energy to convert ammonia to something else.something else.

In Fish most of the ammonia is lost as ammonium In Fish most of the ammonia is lost as ammonium ions(NHions(NH44) across the gills and the kidneys only ) across the gills and the kidneys only excrete a small amount of wasteexcrete a small amount of waste

UreaUrea Since terrestrial animals have to carry their waste around Since terrestrial animals have to carry their waste around

with them ammonia is much too toxic.with them ammonia is much too toxic.

Ammonia is converted to urea by combining COAmmonia is converted to urea by combining CO22 and ammonia. and ammonia.It takes energy to do this and is consequently reflected in their It takes energy to do this and is consequently reflected in their

energy energy budget.budget.

Mammals, adult amphibians and many marine fishes excrete ureaMammals, adult amphibians and many marine fishes excrete urea..

Urea can be excreted in much more concentrated solutions Urea can be excreted in much more concentrated solutions because it is less toxic than ammonia.because it is less toxic than ammonia.

Many amphibians excrete ammonia as tadpoles but switch to urea Many amphibians excrete ammonia as tadpoles but switch to urea as adults.as adults.

Uric AcidUric Acid Land snails, insects, reptiles and birds excrete uric acid.Land snails, insects, reptiles and birds excrete uric acid.

Egg layers and flying organisms that cannot carry a lot of Egg layers and flying organisms that cannot carry a lot of water excrete solid waste only.water excrete solid waste only.

Uric acid is the least toxic and precipitates.Uric acid is the least toxic and precipitates.

Settles to the bottom of the egg to protect growing bird or Settles to the bottom of the egg to protect growing bird or reptile embryo.reptile embryo.

Keeps insects from drying out and makes them light for flight.Keeps insects from drying out and makes them light for flight.

Tortoises can switch from urea to uric acid when there is a Tortoises can switch from urea to uric acid when there is a deficit of water in the environment.deficit of water in the environment.

Osmoconformers Verses Osmoconformers Verses OsmoregulatorsOsmoregulators

There are two solutions to maintaining internal There are two solutions to maintaining internal water balance.water balance.

OsmoconformersOsmoconformers match the osmolarity of the environment. match the osmolarity of the environment.

Osmoregulators Osmoregulators actively absorb or excrete solutes to actively absorb or excrete solutes to maintain a constant internal osmolarity within body tissues.maintain a constant internal osmolarity within body tissues.

The osmolarity of blood is approximately 300 millimoles per The osmolarity of blood is approximately 300 millimoles per liter(mosm/L).liter(mosm/L).

Sea water is approximately 1000 mosm/LSea water is approximately 1000 mosm/L

Extreme EnvironmentsExtreme Environments

Being an osmoregulator is expensive.Being an osmoregulator is expensive.

Most animals are Most animals are stenohaline.stenohaline. Steno means narrow , haline means saltSteno means narrow , haline means salt..

EuryhalineEuryhaline animals can tolerate large animals can tolerate large osmotic fluxuations in their external osmotic fluxuations in their external environment.environment. Eurys means broad(Greek)Eurys means broad(Greek)

Maintaining Water Balance in the Maintaining Water Balance in the SeaSea Invertebrates are osmoconformers.Invertebrates are osmoconformers.

Even though the osmolarity of their tissues match the environment Even though the osmolarity of their tissues match the environment they do regulate the composition of their internal environment. they do regulate the composition of their internal environment. (specific solutes)(specific solutes)

Marine vertebrates except hagfish are osmoregulators.Marine vertebrates except hagfish are osmoregulators.

These animals constantly lose water to the environment.These animals constantly lose water to the environment.

Must drink large amounts of water and excrete excess salts through their Must drink large amounts of water and excrete excess salts through their gills.gills.

Sharks are actually hyperosmotic to their environment because they Sharks are actually hyperosmotic to their environment because they concentrate urea in their tissues. They protect themselvs from the toxicity concentrate urea in their tissues. They protect themselvs from the toxicity of urea with TMAO (trimethylamine oxide).of urea with TMAO (trimethylamine oxide).

Water enters the shark’s body by diffusion so they don’t drink.Water enters the shark’s body by diffusion so they don’t drink.

Maintaining Osmotic Balance In Fresh WaterMaintaining Osmotic Balance In Fresh Water

Fresh water organisms are constantly gaining Fresh water organisms are constantly gaining water because their tissues are hyperosmotic to water because their tissues are hyperosmotic to their environment.their environment.

Fresh water protists (Amoeba and Paramecium) have Fresh water protists (Amoeba and Paramecium) have contractile vacuoles pump the excess water out.contractile vacuoles pump the excess water out.

Most fresh water organisms excrete dilute urine and Most fresh water organisms excrete dilute urine and replenish salt through their diet. replenish salt through their diet.

Salmon osmoregulate while in the ocean by drinking water Salmon osmoregulate while in the ocean by drinking water and excreting slat through their gills and cease drinking and excreting slat through their gills and cease drinking and excrete dilute urine while in fresh water.and excrete dilute urine while in fresh water.

Special Problems Special Problems Anhydrobiosis Anhydrobiosis

Organism completely dehydrates and enters a Organism completely dehydrates and enters a dormant state until water is available again.dormant state until water is available again.

Membrane remains in tact during dehydration Membrane remains in tact during dehydration becausebecause trehalose trehalose (disaccharide) replaces (disaccharide) replaces water.water.

Desert Kangaroo rat lives entirely on water Desert Kangaroo rat lives entirely on water created by their metabolism.created by their metabolism.

Kangaroo Rat from the South West

Osmotic Balance on LandOsmotic Balance on Land Skin and keratinized shells prevent Skin and keratinized shells prevent

animals and insects from drying out.animals and insects from drying out.

Waxy cuticles for plants.Waxy cuticles for plants.

Drink water and eat moist food.Drink water and eat moist food.

Produce metabolic water (mitochondria)Produce metabolic water (mitochondria)

Go out at night time.Go out at night time.

Anhydrobiosis of the Tardigrade

EXCRETORY EXCRETORY SYSTEMSSYSTEMS

OVERVIEWOVERVIEW Body fluid is collected and filteredBody fluid is collected and filtered

Hemolymph, blood, coelomic fluidHemolymph, blood, coelomic fluid

Usually filtered by selectively permeable membranes of Usually filtered by selectively permeable membranes of transport epithelia.transport epithelia.

Large proteins and cells are left behind.Large proteins and cells are left behind.

Hydrostatic pressure forces water and small solutes Hydrostatic pressure forces water and small solutes through.through.

SaltsSalts SugarsSugars Amino acidsAmino acids Nitrogenous wastesNitrogenous wastes

Largely non selective filtering occurs here.Largely non selective filtering occurs here.

Selective absorption or secretionSelective absorption or secretion

Now called the filtrate, its composition Now called the filtrate, its composition adjusted.adjusted.

Active transport is used to selectively Active transport is used to selectively reabsorb essential nutrients.reabsorb essential nutrients.

GlucoseGlucose Some saltsSome salts Amino acidsAmino acids

Wastes are left in the filtrate to be Wastes are left in the filtrate to be excreted.excreted.

Protonephridia of the Flatworm

Metanephridia of the Annelid

Malpighian Tubules of the Insect

Counter Current Exchange

Antidiuretic Hormone Antidiuretic Hormone When there is an increase in When there is an increase in

osmolarity in the blood:osmolarity in the blood: OsmoreceptorsOsmoreceptors present in the present in the

hypothalamus make us feel thirsty.hypothalamus make us feel thirsty.

Antidiuretic Hormone Antidiuretic Hormone is released by is released by the pituitary gland and causes water to the pituitary gland and causes water to be reabsorbed in the collecting duct by be reabsorbed in the collecting duct by increasing its permeability.increasing its permeability.

Rennin Angiotensin Aldosterone Rennin Angiotensin Aldosterone SystemSystem

RAAS RAAS is another mechansim thatis another mechansim that maintains the maintains the osmolarity of the blood.osmolarity of the blood.

The The jusxtaglomerular apparatus jusxtaglomerular apparatus is a patch of is a patch of tissue that within the afferent blood vessel that tissue that within the afferent blood vessel that feeds blood to the glomurulus that responds tto a feeds blood to the glomurulus that responds tto a drop in blood pressure.drop in blood pressure.

In response to this drop in blood pressure the JGA releases In response to this drop in blood pressure the JGA releases reninrenin which turns which turns angiotensinangiotensin into into angiotensin IIangiotensin II. .

Angiotensisn II constricts blood vesseles to increase blood Angiotensisn II constricts blood vesseles to increase blood pressure.pressure.

Aldosterone and the Adrenal GlandsAldosterone and the Adrenal Glands Angiotensis II also stimulates the adenal Angiotensis II also stimulates the adenal

glands located on top of the kidneys to glands located on top of the kidneys to release release AldosteroneAldosterone..

Aldosternone causes NaAldosternone causes Na++ to be reabsorbed in to be reabsorbed in the distal tubule and water follows.the distal tubule and water follows.

Ensures that the blood does not become Ensures that the blood does not become diluted in response to the reabsorption of water.diluted in response to the reabsorption of water.

A hormone called A hormone called atrial natriuretic factoratrial natriuretic factor is is released from the atrium responds to an released from the atrium responds to an increase of blood pressure and is the off switch increase of blood pressure and is the off switch for RAAS.for RAAS.

How the Gradient is How the Gradient is MaintainedMaintained The The juxtamedullary nephronjuxtamedullary nephron uses the uses the

gradient in the kidney to excrete urine gradient in the kidney to excrete urine that is hyperosmotic to the kidney tissue.that is hyperosmotic to the kidney tissue.

The The descending Loop of Henledescending Loop of Henle is is permeable to Hpermeable to H22O but not NaCl.O but not NaCl. As filtrtate moves towards the medulla HAs filtrtate moves towards the medulla H22O O

diffuses out.diffuses out. The filtrate becomes increasing hyperosmotic.The filtrate becomes increasing hyperosmotic. The filtrate has the highest osmolarity at the The filtrate has the highest osmolarity at the

bottom of the loop.bottom of the loop.

The The ascending Loop of Henleascending Loop of Henle is is permeable to salt but not water.permeable to salt but not water. Since the filtrate at this point is Since the filtrate at this point is

hyperosmotic to the kidney NaCl hyperosmotic to the kidney NaCl diffuses out.diffuses out.

This contributes to the high osmolarity This contributes to the high osmolarity of the medulla.of the medulla.

At the upper portion of the ascending At the upper portion of the ascending loop salt moves out through active loop salt moves out through active transport which requires ATPtransport which requires ATP

This ensures that the gradient will not This ensures that the gradient will not dissapte.dissapte.

Counter Current Exchange Also Counter Current Exchange Also Maintains the Gradient Maintains the Gradient

Capillaries that surround the nephron are Capillaries that surround the nephron are called the called the vasa rectavasa recta..

The blood in the capillaries that surround The blood in the capillaries that surround the descending loop of Henle lose water the descending loop of Henle lose water and gain salt.and gain salt.

The blood in the capillaries that surround The blood in the capillaries that surround the ascending loop of Henle lose salt and the ascending loop of Henle lose salt and gain water.gain water.

This helps maintain the gradient in the This helps maintain the gradient in the kidney.kidney.

How Terrestrial Animals Excrete Urine That How Terrestrial Animals Excrete Urine That is Hyperosmoticis Hyperosmotic

When the filtrate reaches the distal tubule it is hypoosmotic When the filtrate reaches the distal tubule it is hypoosmotic because NaCl has been removed by active transport.because NaCl has been removed by active transport.

When the filtrate descends back towards the medulla in the When the filtrate descends back towards the medulla in the collecting ductcollecting duct H H22O diffuses out because the collecting O diffuses out because the collecting duct is permeable to Hduct is permeable to H22O and not salt.O and not salt.

This concentrates salt and urea in the filtrate.This concentrates salt and urea in the filtrate.

Urea leaks out at the bottom of the collecting duct which Urea leaks out at the bottom of the collecting duct which contributes the gradient.contributes the gradient.

The filtrate is isoosmotic to the inner medulla when it The filtrate is isoosmotic to the inner medulla when it empties into the empties into the renal pelvisrenal pelvis but is hyperosmotic to the but is hyperosmotic to the blood and interstitial fluid in the rest of the body.blood and interstitial fluid in the rest of the body.

Special Adaptations of the KidneySpecial Adaptations of the Kidney

Vampire bats can Vampire bats can switch from excreting switch from excreting large amounts of large amounts of dilute urine while dilute urine while feeding to excreting feeding to excreting urine concentrated urine concentrated with urea while with urea while roosting.roosting.

Diverse Adaptations of the Diverse Adaptations of the NephronNephron

Desert animals excrete hyperosmotic urine.Desert animals excrete hyperosmotic urine. Have exceptionally long loops of Henle to allow Have exceptionally long loops of Henle to allow

for maximum absorption of water.for maximum absorption of water.

Maintain steep gradients in the kidney.Maintain steep gradients in the kidney.

Birds have very short loops of Henle and Birds have very short loops of Henle and cannot concentrate urine like mammals cannot concentrate urine like mammals can. They do produce hyperosmotic urine can. They do produce hyperosmotic urine but conserve water by producing uric acid.but conserve water by producing uric acid.

Reptiles Reptiles have only cortical nephrons and produce urine have only cortical nephrons and produce urine that is isoosmotic to body fluids.that is isoosmotic to body fluids.

Epithelium of the Epithelium of the cloacacloaca reabsorb water.reabsorb water.

Excrete uric acid to conserve water as well.Excrete uric acid to conserve water as well.

AmphibiansAmphibians take in water by diffusion through the skin. take in water by diffusion through the skin.

Excrete dilute urine and accumulate salts through the skin Excrete dilute urine and accumulate salts through the skin through active transport.through active transport.

On land frogs reabsorb water through bladder epithelia.On land frogs reabsorb water through bladder epithelia.

Boney Salt water fish are hypoosmotic to their environment Boney Salt water fish are hypoosmotic to their environment and have excretory tubules(no glomuruli or Bowmans and have excretory tubules(no glomuruli or Bowmans capsule).capsule).

Excrete small amounts of concentrated urine.Excrete small amounts of concentrated urine.