10.7

• Groups of animals based on osmoregulation

  • Osmoconformers
  • Osmoregulators
• Osmoconformers


  Those that cannot regulate their osmotic pressure at all
• Osmoregulators


  Those that can regulate their osmotic pressure to some degree
• Marine animals have body fluids that are isotonic with seawater
• Marine animals have little need to osmoregulate
• Marine animals may need to engage in specific ion regulation if their environment changes
• Some marine species live in a more inhospitable estuarine environment
• The concentration of external environment may change from high to low solute levels in estuarine environments
• Animals have powers of osmoregulation but this requires energy
• Animals allow solute concentrations of their body fluids to vary with the external environment
• The bigger tolerance of solute concentrations allowed in cells, the less energy required for osmoregulation
• Structural adaptations for marine organisms

  • Sac like glands
  • Scales
  • Very low kidney filtration rate
  • Active secretion of increased salts
• Sac like glands


  Take up nitrogenous waste and excrete to exterior
• Scales


  Restrict major water loss
• Very low kidney filtration rate results in very little urine containing highly concentrated non-toxic nitrogenous waste
• Active secretion of increased salts is taken up by the body through special glands in the gills
• Freshwater animals live in a hypotonic environment with constant water movement diluting their salt
• Structural adaptations for freshwater organisms

  • Impermeable covering
  • Antennal glands
  • Active absorption of ions
  • High kidney filtration rate
• Impermeable covering


  Like fish scales or arthropod cuticles over permeable areas such as gills and guts
• Antennal glands


  Reabsorb ions that would be eliminated with excess water
• Freshwater crayfish produce watery, hypotonic urine and antennal glands reabsorb salts
• Freshwater organisms have a very high kidney filtration rate and produce a large volume of urine
• Freshwater organisms safely wash toxic ammonia from the body with no energy needed to convert it to a less toxic form
• Terrestrial organisms are osmoregulators
• Terrestrial organisms have to actively control their internal salt concentrations independent of the salt concentration in the environment
• Terrestrial organisms must take in water to replace what is continuously lost in elimination of waste from the body
• Water is also lost from evaporating from the body surface and respiratory tract
• Structural adaptations for terrestrial organisms

  • Waterproof outer surfaces
  • Modification of behaviour
  • Tissues tolerant to water loss
• Waterproof outer surfaces


  Prevents the loss of water in insects and reptiles, e.g., the waxy cuticle of an insect
• Modification of behaviour


  For example, an animal burrowing into the ground during heat or drought and going into aestivation
• Tissues tolerant to water loss

  Fat storage in the hump allows a high level of production of metabolic water through aerobic cellular respiration