Osmoregulation and excretion Flashcards
What do excretory systems do?
Control Volume, Concentration, And Composition Of Body Fluids.
Dispose of Metabolic Waste
What must be maintained for cellular water balence?
the osmolarity of extracellular fluid
Osmolarity of a solution:
The number of moles of active solutes per liter of solvent; expressed as milliosmoles/L (mosm/L),
or milliosmoles/Kg
Average osmolarity of seawater
~3.5% salinity = 35 ppt = 1000mosm/L
Osmoconformers
equilibrate their osmolarity with seawater; many marine invertebrates are osmoconformers.
Osmoregulators
maintain osmolarities lower than seawater.
some marine invertebrates. all freshwater animals and all terrestrial animals.
What is the adaptive value of osmoconformity?
Don’t have to expend energy to osmoregulate, since they don’t osmoregulate.
In high osmolarity, ____ is actively transported out through the gills, and ____ ions follow
Cl-
Na+
In low osmolarity, the transport of___ is reversed into _____
Cl-
active transport.
Are marine invertebrates osmoregulators?
Some of them
TMAO
trimethylamine oxide
stabilizes proteins and cellular structures
In Cartilaginous Fish
(Sharks, rays, and skates) what is their internal fluid osmolarity compared to their environment?
internal fluid is similar in osmolarity to seawater so water is not lost by osmosis to the environment
how do Cartilaginous Fish
(Sharks, rays, and skates) excrete NaCl?
Their rectal gland actively secretes chloride ions, with sodium ions following.
how do Cartilaginous Fish
(Sharks, rays, and skates) Maintain high internal osmolarity?
By accumulating higher than normal levels of urea, and a special metabolite called TMAO*
Anadromous Fish
live Part of their lifecycle in freshwater, and part in saltwater
How do birds excrete salt?
Birds use nasal glands that release salt excretions into the nasal passages
Sea turtles have modified _________
tear ducts they secrete salt into the orbit of the eye.
______ Conserve Some Ions And Excrete Others in order to______
Ionic Regulators
Maintain Ionic Composition
Ammonia
(NH3) is the most common nitrogenous waste; highly toxic at even moderate concentrations.
soluble in water
ammonotelic
aquatic animals that secrete NH3 through their gills
Terrestrial animals must convert NH3 to ______.
urea or uric acid.
How many different types of nitrogenous waste do most species secrete?
Most species secrete more than one nitrogenous waste
Humans are ureotelic but also excrete:
Uric acid—from metabolism of nucleic acids and caffeine.
Ammonia—regulates pH of extracellular fluid by buffering urine.
nitrogenous waste
Carbohydrates and lipids are metabolized to water and CO2 and are easily excreted.
Proteins and nucleic acids contain nitrogen so metabolism produces nitrogenous waste
