TAILIEUCHUNG - Lecture Biology: Chapter 44 - Niel Campbell, Jane Reece

Chapter 44 - Osmoregulation and excretion. 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 Physiological systems of animals operate in a fluid environment. Relative concentrations of water and solutes must be maintained within fairly narrow limits. Osmoregulation regulates solute concentrations and balances the gain and loss of water. Freshwater animals show adaptations that reduce water uptake and conserve solutes. Desert and marine animals face desiccating environments that can quickly deplete body water. Excretion gets rid of nitrogenous metabolites and other waste products. How does an albatross drink saltwater without ill effect? Figure 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. Cells require a balance between osmotic gain and loss of water. Osmolarity = the solute concentration of a solution, determines the movement of water across a selectively permeable membrane. If two solutions are isoosmotic, the movement of water is equal in both directions. If two solutions differ in osmolarity, the net flow of water is from the hypoosmotic to the hyperosmotic solution. Solute concentration and osmosis Selectively permeable membrane Net water flow Hyperosmotic side Hypoosmotic side Water Solutes Figure Osmotic Challenges Osmoconformers, consisting only of some marine animals, are isoosmotic with their surroundings and do not regulate their osmolarity. Osmoregulators expend energy to control water uptake in a hypoosmotic environment and loss in a hyperosmotic environment. Most animals are stenohaline; they cannot tolerate substantial changes in external osmolarity. Euryhaline animals can survive large fluctuations in external osmolarity. Sockeye salmon = euryhaline osmoregulators Figure Marine Animals Most marine invertebrates are osmoconformers. Most marine vertebrates and some invertebrates are osmoregulators. Marine bony fishes are .

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