Lesson 5 Osmoregulation

Question 1

Osmoregulation

Answer 1

Osmoregulation is the control of water potential of body fluids to maintain a constant internal environment in the blood, tissue fluid and cytoplasm.
• Osmoregulation is achieved through the regulation of the water and salt balance of the body fluids.
• Animals may be osmoregulators or osmoconformers. Osmoconformers cannot regulate the control of the water-salt balance.
• Most marine invertebrates are osmoconformers – they have the same solute concentrations in their body fluids as sea water.

Question 2

Osmoregulators

Answer 2

• Land animals, freshwater animals and and marine vertebrates have body
fluids that are different from that of their environment.
• They must actively regulate water movement.
• This regulation is done mainly through the urinary system

Question 3

Freshwater
vs Saltwater
Fish

Answer 3

Freshwater Fish
* Have a much higher solute concentration in their internal fluids than that of their environment.
* Constantly gain water by osmosis through the body surfaces
* Lose salt by diffusion
* Compensates by actively taking in salt through their gills and not drinking water.
* Excess water is released through the production of a large amount of dilute urine.

Question 4

Freshwater
vs Saltwater
Fish

Answer 4

• Saltwater Fish
• Have a lower solute concentration in their internal fluids than that of their
environment.
• Constantly lose water by osmosis through the body surfaces.
• Gains salt by diffusion
• Compensates by pumping out excess salt through their gills and taking in
large amounts of water through drinking
• Saves water by producing only small amounts of concentrated urine.

Question 5

Hormonal Regulation of the Urinary System

Answer 5

• Control of the concentration of water and solutes is done by the action of
hormones on the nephrons of the kidney.
• When dehydration begins, the solute concentration of the body fluids rises.
This causes the pituitary to secrete antidiuretic hormone (ADH).
• Antidiuretic hormone acts on the permeability of the collecting duct.
• When ADH is present the duct develops membrane channels called
aquaporins.
• Aquaporins allow water to be taken back into the blood producing a more concentrated urine.