Download Regulating The Internal Environment

Regulating The Internal
Environment
Homeostasis
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The ability of animals to regulate their
internal environment.
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Thermoregulation - the ability of animals to
regulate their internal temperature.
 Osmoregulation – the ability of animals to
regulate their water balance.
 Excretion – how animal s rid themselves of
nitrogenous wastes.
An Overview of Homeostasis
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Regulators - actively regulate their own
internal environment in response to external.
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Cannot tolerate large internal changes.
Salmon are osmoregulators
Endotherms are thermoregulators
Conformers – allow some conditions to vary in
response to the external environment.
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Live in relatively stable environments and somewhat
conform to their external environment.
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Spider crabs will gain or lose water in reponse to a variation
in salinity.
Regulaters Verses Conformers
No Organism is a Perfect
Conformer or Regulator
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Salmon may osmoregulate but they generally
conform to the external temperatures.
For a particular condition animals may regulate
or conform.
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A forest dwelling lizard may have to travel long
distances to perch in the sun and therefore choose to
regulate its body temperature in the forest to avoid
predation. The same lizard may choose to bask in
the sun in open predation.
Biochemical and Physiological Processes
Vary With Body Temperature.
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Enzyme mediated reactions may vary 2-3 fold for every
10o C temperature increase.
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Q10 effect – multiple by which a particular process increases with
a 10o increase in body temperature.
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Membranes are affected by temperature and can affect
animal unction.
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Glycogen hydrolysis occurs 2.5 greater at 30oC than 20oC then the
Q10 of the reaction is 2.5.
Muscle contractions can be affected and the ability of the animal
to run, jump or fly.
All animals have an optimal temperature in which they
can function.
Physical Processes Account for Heat
Lost or Gained.
Conduction - Direct transfer of heat through
contact with the environment.
Convection - transfer of heat by the movement of
a liquid or gas past a surface.
Radiation - emission of electromagnetic radiation
from objects.
Evaporation – heat removal through evaporation
Heat Exchange
Cool Purple Lizard on a Rock
Ectothermy Verses Endothermy
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Ectotherms generate such little heat through metabolism that their
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Because endotherms can maintain a stable internal temperature
they can sustain prolonged activities.
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Endotherms are also better designed to live on land and can
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A disadvantage of being an endotherm is that they must consume
much more food because of their energy needs.
body temperature is determined by the environment.
tolerate the large fluxuations in temperature.
Endotherms Verses Ectotherms
Physiological Thermoregulation
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Adjusting the rate of heat exchange
between the organism and its
environment.
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Insulation – fur and feather fluffing
Vasodilation – dilate blood vessels at the
surface of the skin to dissapate heat.
Vasoconstriction – constrict blood vessels
to direct blood towards the core and away
from the extremities where heat is lost.
Countercurrent Heat Exchange
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Arrangement of blood vessels are designed to
either trap or release heat more efficiently.
Arteries carrying warm blood from the animal’s
core are in close proximity to the cooler blood in
the veins returning to the core.
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Keeps artic wolf legs from freezing.
By counter current exchange un-insulated toe pads are kept
just above 0 o C to prevent heat loss but not cold enough to
freeze.
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
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Evaporative Cooling
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Behavioral
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Sweating
Panting
Making their bodies wet
Change posture
Migrate
Bask in the sun or go swimming
Changing the rate of metabolic heat production
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Non-shivering thermogenesis
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Brown fat – lipid found in the neck and shoulders of some
animals that create mostly thermal energy
Happy Happy Hippos
Invertebrates
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Mostly thermoconformers
Desert locusts don’t move until they warm up.
Some bees and moths are endothermic
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Flight muscles generate heat
Some shiver to produce heat
Countercurrent exchange
Some bees huddle together when cold
Some bees transport water to the hive and
evaporate the water by fanning their wings.
Adjustment to Changing
Temperatures
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Nerves in the skin sense temperature changes
and the hypothalamus in the brain responds.
Acclimmatization is a physiological response
to temperature change over a period of weeks
or days.
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Grow a thicker coat or shed.
Produce enzymes that work at different temperatures.
Membranes change proportion of saturated verses
unsaturated fatty acids within the phospholipds.
May creates cryoprotectant compounds.
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Cells can make rapid adjustments in
response to extreme stress.
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Heat shock proteins – help maintain the
integrity of other proteins that would
denature under extreme heat.
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The physiological adaptations that animals
make during acclimatization affect their
tolerance to temperature.
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Summer acclimatization of the bull heaeded
cat fish can survive water temperatures of
36oC but cannot function in cold water.
How Animals Deal With
Environmental Extremes
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Torpor is a physiological state in which activity
is low and metabolism decreases.
Hibernation is a long term winter torpor.
Estivation is a long term summer torpor when
sources of water are scarce.
Daily Torpor is a short term torper
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Adpated to feeding patterns.
Shrews feed at night and are inactive during the day.
Appears to be controlled by a biological clock.
The Belding’s squirrel can live on
one Kcal per day while hibernating
Water and Waste
Disposal
Osmoregulation
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Management of the body’s solute
concentration.
Management of water into and out of the
body.
Depends on transport epitheilium.
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Layer or layers of specialized cells that
regulate solute movements in a particular
direction and in certain quantities.
Structure Verses Function
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Some of these epitheilia
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Face outwards
Line openings
Are arranged in tubular networks that have
large surface areas.
Joined by tight junctions to create barriers
between the environment and body tissue
Salt Excreting glands in Birds
The Nature of Nitrogenous Waste
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Nitrogenous wastes are created through
de-amination, the removal of an amine
group from of proteins and nucleic acids.
Primary toxic product is ammonia.
These wastes must be dissolved in water
and therefore affect the water balance.
Nitrogenous Waste Depends on Habitat
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The kinds of nitrogenous waste an animal excretes
depends on the availability of water in its habitat and
evolutionary history.
The amount and composition of waste produced
depends on energy needs and diet.
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Endotherms have high energy needs and consequently excrete
more than ectotherms.
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Carnivores take in large amounts of protein and excrete large
amounts of nitorgenous watse.
Ammonia
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Animals that live in the water can excrete ammonia.
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They can simply swim away from their waste.
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Requires less energy to convert ammonia to something
else.
In Fish most of the ammonia is lost as ammonium
ions(NH4) across the gills and the kidneys only excrete a
small amount of waste
Urea
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Since terrestrial animals have to carry their waste around with them
ammonia is much too toxic.
Ammonia is converted to urea by combining CO2 and ammonia.
It takes energy to do this and is consequently reflected in their energy
budget.
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Mammals, adult amphibians and many marine fishes excrete urea.
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Urea can be excreted in much more concentrated solutions because it is
less toxic than ammonia.
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Many amphibians excrete ammonia as tadpoles but switch to urea as
adults.
Uric Acid
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Land snails, insects, reptiles and birds excrete uric acid.
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Egg layers and flying organisms that cannot carry a lot of water
excrete solid waste only.
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Uric acid is the least toxic and precipitates.
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Settles to the bottom of the egg to protect growing bird or reptile
embryo.
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Keeps insects from drying out and makes them light for flight.
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Tortoises can switch from urea to uric acid when there is a deficit of
water in the environment.
Osmoconformers Verses Osmoregulators
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There are two solutions to maintaining internal water
balance.
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Osmoconformers match the osmolarity of the environment.
Osmoregulators actively absorb or excrete solutes to maintain a
constant internal osmolarity within body tissues.
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The osmolarity of blood is approximately 300 millimoles per
liter(mosm/L).
Sea water is approximately 1000 mosm/L
Extreme Environments
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Being an osmoregulator is expensive.
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Most animals are stenohaline.
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Steno means narrow , haline means salt.
Euryhaline animals can tolerate large osmotic
fluxuations in their external environment.
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Eurys means broad(Greek)
Maintaining Water Balance in the Sea
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Invertebrates are osmoconformers.
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Even though the osmolarity of their tissues match the environment they do
regulate the composition of their internal environment. (specific solutes)
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Marine vertebrates except hagfish are osmoregulators.
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These animals constantly lose water to the environment.
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Must drink large amounts of water and excrete excess salts through their gills.
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Sharks are actually hyperosmotic to their environment because they concentrate urea
in their tissues. They protect themselvs from the toxicity of urea with TMAO
(trimethylamine oxide).
Water enters the shark’s body by diffusion so they don’t drink.
Maintaining Osmotic Balance In Fresh Water
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Fresh water organisms are constantly gaining water
because their tissues are hyperosmotic to their
environment.
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Fresh water protists (Amoeba and Paramecium) have contractile
vacuoles pump the excess water out.
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Most fresh water organisms excrete dilute urine and replenish
salt through their diet.
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Salmon osmoregulate while in the ocean by drinking water and
excreting slat through their gills and cease drinking and excrete
dilute urine while in fresh water.
Special Problems
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Anhydrobiosis
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Organism completely dehydrates and enters a
dormant state until water is available again.
Membrane remains in tact during dehydration
because trehalose (disaccharide) replaces water.
Desert Kangaroo rat lives entirely on water created by
their metabolism.
Kangaroo Rat from the South West
Osmotic Balance on Land
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Skin and keratinized shells prevent animals and
insects from drying out.
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Waxy cuticles for plants.
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Drink water and eat moist food.
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Produce metabolic water (mitochondria)
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Go out at night time.
Anhydrobiosis of the Tardigrade
EXCRETORY
SYSTEMS
OVERVIEW
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Body fluid is collected and filtered
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Hemolymph, blood, coelomic fluid
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Usually filtered by selectively permeable membranes of transport
epithelia.
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Large proteins and cells are left behind.
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Hydrostatic pressure forces water and small solutes through.
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Salts
Sugars
Amino acids
Nitrogenous wastes
Largely non selective filtering occurs here.
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Selective absorption or secretion
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Now called the filtrate, its composition
adjusted.
Active transport is used to selectively reabsorb
essential nutrients.
Glucose
 Some salts
 Amino acids
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Wastes are left in the filtrate to be excreted.
Protonephridia of the Flatworm
Metanephridia of the Annelid
Malpighian Tubules of the Insect
Counter Current Exchange
Antidiuretic Hormone
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When there is an increase in osmolarity in
the blood:
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Osmoreceptors present in the hypothalamus
make us feel thirsty.
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Antidiuretic Hormone is released by the
pituitary gland and causes water to be
reabsorbed in the collecting duct by
increasing its permeability.
Rennin Angiotensin Aldosterone System
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RAAS is another mechansim that maintains the
osmolarity of the blood.
The jusxtaglomerular apparatus is a patch of tissue
that within the afferent blood vessel that feeds blood to
the glomurulus that responds tto a drop in blood
pressure.
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In response to this drop in blood pressure the JGA releases
renin which turns angiotensin into angiotensin II.
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Angiotensisn II constricts blood vesseles to increase blood
pressure.
Aldosterone and the Adrenal Glands
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Angiotensis II also stimulates the adenal glands
located on top of the kidneys to release
Aldosterone.
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Aldosternone causes Na+ to be reabsorbed in the
distal tubule and water follows.
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Ensures that the blood does not become diluted in
response to the reabsorption of water.
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A hormone called atrial natriuretic factor is
released from the atrium responds to an increase of
blood pressure and is the off switch for RAAS.
How the Gradient is Maintained
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The juxtamedullary nephron uses the
gradient in the kidney to excrete urine
that is hyperosmotic to the kidney tissue.
The descending Loop of Henle is
permeable to H2O but not NaCl.
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As filtrtate moves towards the medulla H2O
diffuses out.
The filtrate becomes increasing hyperosmotic.
The filtrate has the highest osmolarity at the
bottom of the loop.
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The ascending Loop of Henle is
permeable to salt but not water.
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Since the filtrate at this point is hyperosmotic
to the kidney NaCl diffuses out.
This contributes to the high osmolarity of the
medulla.
At the upper portion of the ascending loop
salt moves out through active transport which
requires ATP
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This ensures that the gradient will not dissapte.
Counter Current Exchange Also
Maintains the Gradient
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Capillaries that surround the nephron are called
the vasa recta.
The blood in the capillaries that surround the
descending loop of Henle lose water and gain
salt.
The blood in the capillaries that surround the
ascending loop of Henle lose salt and gain water.
This helps maintain the gradient in the kidney.
How Terrestrial Animals Excrete Urine That is
Hyperosmotic
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When the filtrate reaches the distal tubule it is hypoosmotic because
NaCl has been removed by active transport.
When the filtrate descends back towards the medulla in the
collecting duct H2O diffuses out because the collecting duct is
permeable to H2O and not salt.
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This concentrates salt and urea in the filtrate.
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Urea leaks out at the bottom of the collecting duct which contributes
the gradient.
The filtrate is isoosmotic to the inner medulla when it empties into
the renal pelvis but is hyperosmotic to the blood and interstitial
fluid in the rest of the body.
Special Adaptations of the Kidney
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Vampire bats can
switch from excreting
large amounts of
dilute urine while
feeding to excreting
urine concentrated
with urea while
roosting.
Diverse Adaptations of the Nephron
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Desert animals excrete hyperosmotic urine.
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Have exceptionally long loops of Henle to allow for
maximum absorption of water.
Maintain steep gradients in the kidney.
Birds have very short loops of Henle and cannot
concentrate urine like mammals can. They do
produce hyperosmotic urine but conserve water
by producing uric acid.
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Reptiles have only cortical nephrons and produce urine that is
isoosmotic to body fluids.
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Epithelium of the cloaca reabsorb water.
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Excrete uric acid to conserve water as well.
Amphibians take in water by diffusion through the skin.
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Excrete dilute urine and accumulate salts through the skin through
active transport.
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On land frogs reabsorb water through bladder epithelia.
Boney Salt water fish are hypoosmotic to their environment and
have excretory tubules(no glomuruli or Bowmans capsule).
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Excrete small amounts of concentrated urine.