Biology 172 FINAL EXAM Homeostasis: Osmoregulation and Excretion

  1. chemical changes that may exert a profound effect on the regulation of the chemical reactions that sustain life (5)
    • a. changes in solute concentrations (e.g., osmotic changes)
    • b. changes is salt (electrolyte) composition
    • c. changes in acidity/alkalinity (pH) 
    • d. changes in oxygen concentrations
    • e. changes in toxic waste concentrations
  2. 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)
    ammonia (NH3)
  3. 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
    urea (CO(NH2)2)
  4. 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
    uric acid (C5H4O3N4)
  5. 5 Functions of Excretory Systems in Animals
    • 1. elimination of metabolic wastes
    • 2. regulation of water and solute balance
    • 3. regulation of blood pressure
    • 4. regulation of plasma electrolytes
    • 5. maintenance of plasma pH
  6. What is an osmoregulator?
    regulates osmotic balance of internal fluids
  7. osmoconformer:
    cannot regulate osmotic balance; solute concentrations of internal fluids reflect those outside the animal
  8. euryhaline:
    tolerates a broad range of salinities
  9. stenohaline:
    can only survive within a narrow range of salinities
  10. 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
  11. marine invertebrates that occupy habitats that fluctuate extensively in salinity (estuaries, tide pools, coastal environments) are most likely..
  12. problems faced
    1) osmotic uptake of water
    2) loss of salt ions due to diffusion
    thus all freshwater invertebrates must be...
  13. some mechanisms to facilitate osmoregulation (4)
    • 1) contractile vacuoles (e.g., freshwater protozoans and sponges)
    • 2) protonephridia (e.g., flatworms)
    • 3) waterproof coverings over body surfaces (e.g., crustaceans, aquatic insects, snails)
    • 4) kidneys that produce dilute urine
  14. freshwater fish's body fluids ______ to surrounding freshwater
  15. freshwater fish:
    1) osmotic uptake of water across gill epithelium
    2) diffusional losses of salts
    Adaptations? (4)
    • 1) active transport of salts into blood by gill epithelium
    • 2) do not drink
    • 3) kidneys with short loops of Henle produce a dilute (hypotonic) urine
    • 4) skin surface relatively impermeable to water
  16. marine fish's body fluids _______ to surrounding seawater
  17. marine fish:
    1) dehydration due to osmotic loss of water across gill epithelium
    2) diffusion of salts into blood stream
    Adaptations? (5)
    • 1) active transport of salts out of blood into surrounding seawater
    • 2) drink plenty of seawater
    • 3) intestinal lining absorbs water while minimizing the uptake of salts
    • 4) kidneys with long loops of Henle produce a very hypertonic urine
    • 5) skin relatively impermeable to water
  18. sharks exhibit different adaptation to hypertonic seawater (2)
    • 1) accumulate urea to balance osmotic pressure of surrounding seawater
    • 2) also produce trimethylamine oxide (TMAO) to protect proteins from urea damage
  19. protein catabolism results in the production of
    toxic ammonia
  20. 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)
    elimination of ammonia
  21. 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
  22. 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
  23. 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
  24. 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
    reptiles and birds
  25. vertebrate kidney cortex contains...
    glomeruli and convoluted tubules
  26. kidney's glomeruli are...
    sites of ultrafiltration
  27. kidney's convoluted tubules involved in...
    selective resorption and secretion
  28. medulla composed of...
    renal pyramids with loops of Henle and collecting ducts
  29. loops of Henle involved with...
    generating a salt concentration gradient within renal pyramid
  30. collecting ducts do what?
    collect urine from nephrons and regulate water content of urine
  31. an open space into which collecting ducts drain urine into ureter
  32. Nephron
    basic unit of the kidney
  33. each human kidney with approximately ______ nephrons
  34. 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
  35. a) includes water, small soluble organic molecules (e.g., glucose and amino acids), and mineral ions
    b) excludes cells and plasma proteins
    urinary filtrate
  36. 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)
  37. a) mainly mineral ions in response to hormonal factors
    b) reptiles and birds: uric acid secreted by tubules
  38. 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
    proximal convoluted tubule
  39. 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
    loop of Henle
  40. 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
    Loop of Henle descending limb
  41. 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
    Loop of Henle ascending limb
  42. 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
  43. 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
    collecting ducts
  44. 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
    antidiuretic hormone (ADH or vasopressin)
  45. 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
    juxtaglomerular apparatus
  46. 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
    renin converts angiotensinogen to angiotensin II which produces the following effects
  47. 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
    atrial natriuretic factor (ANF)
Card Set
Biology 172 FINAL EXAM Homeostasis: Osmoregulation and Excretion
Biology 172 FINAL EXAM Homeostasis: Osmoregulation and Excretion