Biology 172 FINAL EXAM Homeostasis: Osmoregulation and Excretion

chemical changes that may exert a profound effect on the regulation of the chemical reactions that sustain life (5)

Nitrogenous Wastes
a. eliminates one nitrogen atom per molecule
b. very toxic and requires lots of water to eliminate
c. characteristic excretory product of aquatic organisms (e.g., fish and amphibians)

Nitrogenous Wastes
a. eliminates two nitrogen atoms per molecule
b. far less toxic and requires less water for elimination
c. energetically costly
d. characteristic excretory product of mammals and sharks

Nitrogenous Wastes
a. eliminates four nitrogen atoms per molecules
b. eliminated as a semi-solid paste, requiring very little water
c. energetically most costly
d. characteristic excretory product of birds, reptiles, & insects

5 Functions of Excretory Systems in Animals

What is an osmoregulator?

osmoconformer:

euryhaline:

stenohaline:

for most, the body fluid concentrations of solutes reflect the composition of the surrounding seawater (i.e., most are, especially oceanic species, osmoconformers)

marine invertebrates that occupy habitats that fluctuate extensively in salinity (estuaries, tide pools, coastal environments) are most likely..

problems faced
1) osmotic uptake of water
2) loss of salt ions due to diffusion
thus all freshwater invertebrates must be...

some mechanisms to facilitate osmoregulation (4)

freshwater fish's body fluids ______ to surrounding freshwater

freshwater fish:
problems
1) osmotic uptake of water across gill epithelium
2) diffusional losses of salts
Adaptations? (4)

marine fish's body fluids _______ to surrounding seawater

marine fish:
problems
1) dehydration due to osmotic loss of water across gill epithelium
2) diffusion of salts into blood stream
Adaptations? (5)

sharks exhibit different adaptation to hypertonic seawater (2)

protein catabolism results in the production of

1) requires copious amounts of water
2) each ammonium ion has only one nitrogen atom
3) only suitable for excretion by aquatic animals or those with unlimited access to water (e.g., amphibians)

What organism?
1) paired metanepridia open into coelomic space of segment via nephrostome
2) metanephridial tubule passes into posterior segment in which tubular absorption and secretion modifies the urine
3) dilute urine is produced
4) water losses offset through water uptake by the integument

What organism?
1) Malpighian tubules connected to midgut with blind ends in hemolymph
2) wastes (uric acid), salts, and water pass into tubules from hemolymph
3) tubule contents enter into midgut and passed out through the anus
4) intestinal resorption of water conserves water losses

what organism?
1) convert ammonia to urea
2) requires less water to remove
3) also much less toxic than is ammonia
4) each urea with two nitrogen atoms
5) however, urea formation requires energy expenditures by the animal

What organism?
1) convert ammonia wastes to uric acid
2) conversion is energetically very expensive 3) each uric acid molecule with four nitrogen atoms
4) may be eliminated as a semi-solid paste requiring very little water
5) ideal for animals living in very arid environments
6) some marine birds possess salt-excreting nasal glands that utilize a countercurrent exchange mechanism

vertebrate kidney cortex contains...

kidney's glomeruli are...

kidney's convoluted tubules involved in...

medulla composed of...

loops of Henle involved with...

collecting ducts do what?

an open space into which collecting ducts drain urine into ureter

Nephron

each human kidney with approximately ______ nephrons

1) afferent arteriole into glomerulus with greater diameter than efferent arteriole
2) hydrostatic pressure of blood in glomerulus results in ultrafiltration into surrounding space of Bowman's capsule

a) includes water, small soluble organic molecules (e.g., glucose and amino acids), and mineral ions
b) excludes cells and plasma proteins

a) glucose and amino acids completely reabsorbed
b) others, e.g., water and mineral ions, are regulated to maintain homeostasis – amount of reabsorption changes to adjust to dietary intake (under hormonal control)

a) mainly mineral ions in response to hormonal factors
b) reptiles and birds: uric acid secreted by tubules

a) secretion of hydrogen ion, ammonium and toxins from blood into lumen of tubule
b) reabsorption of sodium, chloride, bicarbonate, sugar, amino acids, and water back into the blood

a) concentration of salt in urine increases towards bottom of loop
b) concentration gradient results from countercurrent mechanism plus the active secretion of sodium from ascending portion of the loop
c) results in concentration gradient towards the bases of the renal pyramids
d) descending limb
e) ascending limb

1) transport epithelium freely permeable to water but not to salt and other solutes
2) water diffuses out of tubule because interstitial fluid hyperosmotic to fluid in tubule

1) transport epithelium permeable to salt but not to water
2) thin segment: NaCl diffuses out of tubule into interstitial fluid
3) thick segment: NaCl actively pumped out of tubule into interstitial fluid

1) hormone from the adrenal glands
2) stimulates reabsorption of sodium ion and secretion of potassium ions
3) ultimately leads to increasing water reabsorption and increasing blood pressure
4) also regulates plasma pH by secreting hydrogen ion and reabsorbing bicarbonate
b) important in the regulation of sodium and potassium ion concentrations in the blood

a) run parallel to loops of Henle and the concentration gradients in the renal pyramids
b) tendency is for urine to lose water through collecting duct walls
c) by regulating permeability of collecting duct walls to water, can regulate concentration of urine

a. produced in hypothalamus and stored in the posterior pituitary gland
b. hypothalamus responds to increased osmolarity of the blood
c. ADH increases permeability of walls of collecting ducts which conserves water losses
d. involves negative feedback
e. alcohol inhibits release of ADH leading to dehydration

a. specialized tissue located in the afferent arteriole
b. part of the renin-angiotensin-aldosterone system (RAAS)
c. releases enzyme renin when blood pressure in afferent arteriole drops
d. renin converts angiotensinogen to angiotensin II

1) general arteriole constriction
2) stimulates proximal tubule to reabsorb more water & NaCl
3) causes adrenal glands to release aldosterone which results in Na+ and water reabsorption by the distal tubules
4) net effect is to increase blood volume and blood pressure

a. produced from the walls of the heart atria in response to increase in blood volume and pressure
b. inhibits the release of renin by JGA