Transcript DNA Technology - Loyalsock Township School District

Ch. 44
A Balancing Act
Maintaining the fluid environment of cells,
tissues, and organs is critical
Achieved by…
• Osmoregulation
– General term for the processes by which animals
control solute concentrations and balance water
gain and loss
• Excretion
– Process that rids the body of nitrogenous
metabolites and other metabolic waste products
Osmosis and Osmolarity
Osmolarity
• Total solute concentration
expressed as molarity (mols
of solute/liter of solution)
• Isoosmotic
– Equal concentrations
• Hyperosmotic
– The solution with greater
solute
• Hypoosmotic
– The solution with less solute
Osmotic Challenges
Osmoconformer
• Isoosmotic with
surroundings
• Marine animals
Osmoregulator
• Control internal
osmolarity independent of
the environment
• Freshwater and terrestrial
habitats
Stenohaline vs. Euryhaline
Animals that Live in Waters
Animals that Live in Temporary Waters
Desiccation
• Extreme dehydration is fatal for most animals
Anhydrobiosis
• Dormant state due to drying up of their habitat
• Tardigrades (water bears)
Land Animals
Body coverings prevent dehydration
• Waxy exoskeletons, shells, keratinized skin
Mainly lose water by…
1. Urine and feces
2. Across the skin
3. Surfaces of gas exchange organs
Forms of Nitrogenous Wastes
Ammonia
• aquatic animals
– Mainly excreted by the gills; little by the kidney
• unsuitable for terrestrial b/c it requires lots of
water and is extremely toxic if not excreted
quickly
Urea
• Low toxicity but energy costly
• ammonia combines with CO2 in the liver
Forms of Nitrogenous Wastes
Uric acid
• land snails, insects,
birds, and many
reptiles
• Relatively nontoxic
but the most costly
in energy
• much less soluble in
water
• usually eliminated in
a pastelike form
along with feces
Excretory System
Diversity of Excretory Systems
Flatworms
• have neither a circulatory
system or coelom
• protonephridium instead
Protonephridium
• network of closed tubules
lacking internal openings that
branch throughout the body
• smallest branches capped by
flame bulbs
Diversity of Excretory Systems
Metanephridia
•
•
•
•
most annelids
excretory tubules in each
segment that have internal
openings to collect body
fluids
capillaries surround the
metanephridium
empties outside the body
through the nephridiopore
Diversity of Excretory Systems
Malpighian tubules
•
•
•
insects, terrestrial arthropods
remove nitrogenous wastes from the hemolymph
empties via the rectum
Excretory Systems
Urine production – 2 steps
1. Filtration of body fluids
2. Modification of filtrate
• selective reabsorption of solutes from the
filtrate back into body fluids
• selective secretion of solutes from body
fluids into the filtrate
Excretory Processes
1. Filtration
– Water and solutes are forced
by pressure out of the blood
and into the excretory
tubule
2. Reabsorption
– Valuable substances are
transported from the filtrate
back to body fluids
3. Secretion
4. Excretion
Excretory Processes
1. Filtration
2. Reabsorption
3. Secretion
– toxins, and excess ions are
extracted from body fluids
and added to the excretory
tubule
4. Excretion
– Altered filtrate (urine)
leaves the system and the
body
Diversity of Excretory Systems
Vertebrate kidneys
• compact organs
• large numbers of
non-segmentally
arranged tubules
• dense capillary
network
Mammalian Kidneys
Pair of bean shaped organs
• 10 cm long
Renal artery
• blood enters the kidney
Renal vein
• blood exits the kidney
Urine  ureter  u. bladder
 urethra (sphincter muscles
control urination)
Mammalian Kidneys
• Renal cortex and renal medulla
Nephrons
• functional unit of the kidney
• long tubule with associated capillaries
Urine formation
• Filtration
• Reabsorption
• Secretion
Mammalian Kidneys
Filtration
• Blood pressure forces fluid
(water, salts, urea, and other
small molecules) into the
kidneys (nephrons)
• Capillaries nonselectively
filter out blood cells and large
molecules
• Small molecules enter the
nephron
•Filtrate produced
– glucose, salts, vitamins,
nitrogenous wastes, and
small molecules
Reabsorption
•Selective transport of
filtrate substances back
into the interstitial fluid
•Reclaims essential small
molecules
– sugars, vitamins,
organic nutrients,
water
• Beneficial substances back
into body and nonuseful
and waste substances into
kidneys for excretion
Secretion
• Plasma is added to the
filtrate
• Very selective process
– utilizes both active
and passive transport
•Collecting duct receives
processed filtrate and
transfers urine to renal
pelvis
A Closer Look at the Nephron
Proximal Tubule
•Reabsorption of ions
Descending Loop of Henle
•Reabsorption of H2O (aquaporins)
Ascending Loop of Henle
•Impermeable to water, NaCl leaves
Distal tubule
•Regulates K+ and NaCl
concentrations
Collecting duct
•Sends urine to renal pelvis
•Some water reabsorption
Adaptations of the Vertebrate Kidney
to Diverse Environments
Mammals 
Nephrons ability to get rid of waste and not
squander water
Extra long loop of Henle producing extremely
concentrated urine
Short loops for aquatic mammals
Reptiles 
Nephrons to conserve water
Uric acid is the main nitrogen waste molecule
Cloaca
Adaptations of the Vertebrate Kidney
to Diverse Environments
Freshwater Fishes and Amphibians 
Many nephrons and long loop of Henle
Must secrete excess water continuously
Produce filtrate at a high rate
Marine Bony Fishes 
Few and small nephrons lacking a distal
tubule
Low filtration rate…small glomeruli
Hormonal Circuits (negative feedback
and transduction pathways) - ADH
Hormonal Circuits –
Renin-Angiotensin-Aldosterone System
JGANetwork of
specialized
tissues of cells
and around
afferent
arteriole;
supplies blood
to glomerulus;
releases renin
Summary