Osmoregulation

Question 1

Marine Elasmobranch Osmoregulation

Answer 1

ECF isosmotic to seawater but with a lower NaCl concentration (made possible by urea)
Therefore NaCl gained at gills and must be excreted at rectal gland cells

Question 2

Marine telocast fish Osmoregulation

Answer 2

Maintain ECF hyperosmotic to seawater (more dilute)
Therefore loose water and gain salt at the gills
Water is taken up through ingestion
Salt is secreted by chloride cells

Question 3

Freshwater Telocast fish Osmoregulation

Answer 3

Have ECF that is hyperosmotic to seawater
Therefore gain water and loose salt
Pavement cells carry out active Na absorbtion

Question 4

Birds Osmoregulation

Answer 4

Have a mixture of mammal and reptile nephrons (so have loops of henle)
Also have an extra organ: cloaca, to make concentrated urine

Question 5

Amphibian osmoregulation

Answer 5

Skin acts as osmoregulatory organ
Water is gained across the skin and salts are lost (hypoosmotic ECF)
Kidneys are used to remove excess water by producing very hypoosmotic urine

Question 6

Insects Osmoregulation

Answer 6

Consume very little water - rely on metabolic water production
Not pressurised heamolymph so cannot carry out filtration
Urine is formed in Malphighian tubules and modified in the hindgut
Active KCl secretion into lumen of Malphigan tubules draws water out
Flows to hindgut where ions are reabsorbed, driving water uptake, and returned to Malphigian tubules to be reused (ion recycling)