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Wize University Biology Textbook > Animal Physiology

Osmoregulation

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Osmoregulation

It is necessary to keep the concentration of water and solutes constant in animal bodies


  • Osmoregulation: controlling the solute and water concentration in bodies
  • Osmolarity: the concentration of solutes in a solution
  • Excretion: getting rid of toxic waste (nitrogen)
  • Animals fall into two catergories
  • Osmoregulator: controls internal solute concentrations
  • Most vertebrates
  • Osmoconformer: does not control solutes, body is the same as the environment
  • Most invertebrates










Photo by Kare Kare | CC BY

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Controlling Osmotic Balance

  • Stenohaline: Can not tolerate large shifts in outside osmolarity
  • Euryhaline: can tolerate large shifts in outside osmolarity
  • Transport epithelium: layers of specialized cells that regulate solute movements
  • Tight junctions: prevent fluid leaks between transport epithelial cells
  • Transport into tubular networks (countercurrent exchanges)
  • Anhydrobiosis: ability to survive in a dormant state when environment dries up - Example: Tardigrades (water bears) can even survive in space
Photo by Willow Gabriel | CC BY


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Osmotic Balance on Land

  • Adaptations to reduce desiccation
  • Desiccation: water lost to the environment Examples: Body coverings, nocturnal activity
  • Kidneys
  • Organs that are essential to mammalian water-balance and osmoregulation
  • Reduce water-loss
  • Excrete nitrogenous waste






Photo by OpenStax College | CC BY
What type of osmoregulation best describes vertebrates?
checklist
Mark Yourself Question
  1. Grab a piece of paper and try this problem yourself.
  2. When you're done, check the "I have answered this question" box below.
  3. View the solution and report whether you got it right or wrong.
Describe a scenario where anhydrobiosis would be beneficial.
Extra Practice
An organism that can tolerate substantial external osmolarity changes is a/an _________.
Example: Circulatory Systems Fishes
1. How many chambers does the fish heart have and how many circuits?
2. What type of current exchange (direction of blood and water flow) do you find in the fish gill and why is this the optimal flow?
3. What derived trait associated with the gills appears in bony fish?
Which of the following animals excrete nitrogenous waste as uric acid?
Example: Nitrogenous Waste
1. What organ is responsible for filtering nitrogenous waste from the blood? and specific structure performs the filtering function?
2. How toxic are each of the three nitrogenous waste products?
3. Why do the amniotes required a non-toxic waste product?
Excretion of salt ions from gills (active transport) is a method of osmoregulation used by what type of organism?
Which of the following describes freshwater osmoregulators?
An organism that can tolerate substantial external osmolarity changes is a/an _________.
Which of the following is true for an ocean osmoconformer?
How do fish in salt water osmoregulate?
Which of the following best describes organisms that cannot tolerate substantial changes in external osmolarity?