Transcript Osmoregulation

Osmoregulation
The Balance between the
uptake and loss of water
and solutes
Draw a diagram to represent
the following:
A starfish egg is isotonic to salt water.
 The Starfish egg is placed in freshwater.
 Use the words hypotonic, hypertonic,
solute, solvent (water) and indicate the
direction that water moves
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The function of
osmoregulation
Maintain the composition of the
cytoplasm of the body’s cells
 Manage the composition of the internal
body fluid that bathes the cells
 Manage the solute and water
composition of blood (in vertebrates)
 Remove toxic metabolic waste products
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All animals produce
nitrogenous wastes
When proteins and nucleic acids are
broken down, ammonia (NH3) is
produced.
 Ammonia is toxic and must be removed.
 Endotherms eat more food—produce
more waste.
 Predators produce more waste than
herbivores.
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Forms of nitrogenous wastes
Ammonia—primarily excreted by
aquatic organisms that have access to
large quantities of water.
 Extremely toxic
 Requires extreme dilution
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Forms of nitrogenous wastes
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Urea—Excreted by mammals, adult
amphibians, marine fish, and turtles.
Produced by the liver, carried by blood to the
kidneys.
100,000 times less toxic than ammonia.
Doesn’t have to be as diluted as ammonia
Animals must expend energy to produce it
from ammonia.
Forms of nitrogenous wastes
Uric Acid—Produced by land snails,
insects, birds, and many reptiles
 Relatively nontoxic
 Largely insoluble in water and is
excreted as a semisolid paste with very
little water loss.
 Even more energy costly than urea
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Osmolarity
Osmotic Pressure
 Moles of solute per liter of solution
 Unit is milliosmoles per liter (mosm/L)
 Concentration of human blood = 300
mosm/L
 Concentration of salt water = 1,000
mosm/L.
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Regulating Osmolarity
Osmoconformers—Animals which do not
actively adjust its internal osmolarity. Only
some marine animals.
 Osmoregulators—animals which must control
its internal osmolarity, because its body fluids
are no isoosmotic with the environment.
Costs lots of energy.
 The greater the difference in concentration—
the greater the energy cost.
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Water Balance in the Sea
Salt water is dehydrating
 Marine bony fish constantly lose water
to their environment
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Water Balance in Fresh Water
Freshwater animals constantly gain
water.
 Contractile Vacuoles?
 Freshwater fish excrete large amounts
of very dilute urine and regain salts
from their food.
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Water Balance on Land
The threat of dessication (drying out) is
the greatest regulatory threat to
terrestrial plants and animals.
 Most animals have body coverings to
prevent dehydration
 Many are nocturnal
 Others drink and eat water and use
metabolic water
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Homework
Draw and label the human excretory system
(Fig. 44.21 first diagram)
 Draw and label a nephron (Fig. 44.21
diagram in bottom left)
 Trace fluid through the nephron explaining
what happens in Bowman’s capsule, the
proximal tubule, Henle’s Loop, the Distal
tubule, and the collecting duct
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