This chapter distinguish between the following terms: isoosmotic, hyperosmotic, and hypoosmotic; osmoregulators and osmoconformers; stenohaline and euryhaline animals; define osmoregulation, excretion, anhydrobiosis; compare the osmoregulatory challenges of freshwater and marine animals;. | Chapter 44 Osmoregulation and Excretion Overview: A balancing act The physiological systems of animals Operate in a fluid environment The relative concentrations of water and solutes in this environment Must be maintained within fairly narrow limits Freshwater animals Show adaptations that reduce water uptake and conserve solutes Desert and marine animals face desiccating environments With the potential to quickly deplete the body water Figure Osmoregulation Regulates solute concentrations and balances the gain and loss of water Excretion Gets rid of metabolic wastes Concept : Osmoregulation balances the uptake and loss of water and solutes Osmoregulation is based largely on controlled movement of solutes Between internal fluids and the external environment Osmosis Cells require a balance Between osmotic gain and loss of water Water uptake and loss Are balanced by various mechanisms of osmoregulation in different environments Osmotic Challenges Osmoconformers, which are only marine animals Are isoosmotic with their surroundings and do not regulate their osmolarity Osmoregulators expend energy to control water uptake and loss In a hyperosmotic or hypoosmotic environment Most animals are said to be stenohaline And cannot tolerate substantial changes in external osmolarity Euryhaline animals Can survive large fluctuations in external osmolarity Figure Marine Animals Most marine invertebrates are osmoconformers Most marine vertebrates and some invertebrates are osmoregulators Marine bony fishes are hypoosmotic to sea water And lose water by osmosis and gain salt by both diffusion and from food they eat These fishes balance water loss By drinking seawater Figure Gain of water and salt ions from food and by drinking seawater Osmotic water loss through gills and other parts of body surface Excretion of salt ions from gills Excretion of salt ions and small amounts of water in scanty urine from kidneys (a) Osmoregulation in a saltwater fish Freshwater . | Chapter 44 Osmoregulation and Excretion Overview: A balancing act The physiological systems of animals Operate in a fluid environment The relative concentrations of water and solutes in this environment Must be maintained within fairly narrow limits Freshwater animals Show adaptations that reduce water uptake and conserve solutes Desert and marine animals face desiccating environments With the potential to quickly deplete the body water Figure Osmoregulation Regulates solute concentrations and balances the gain and loss of water Excretion Gets rid of metabolic wastes Concept : Osmoregulation balances the uptake and loss of water and solutes Osmoregulation is based largely on controlled movement of solutes Between internal fluids and the external environment Osmosis Cells require a balance Between osmotic gain and loss of water Water uptake and loss Are balanced by various mechanisms of osmoregulation in different environments Osmotic Challenges Osmoconformers, which are only
