My_Ch44_lecture_rev09(2009050122141076) - Chapter 44:...

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Chapter 44: Osmoregulation and Excretion Purpose—to understand osmoregulation (water balance) and excretory system function What you MUST know in Ch 44: Marine vs. freshwater fish Forms of nitrogenous waste (remember, this isn’t my idea!) Survey of excretory systems Nephron structure and function Mammalian kidney and conserving water Regulation of kidney function The chapter starts out with thermoregulation—read and review it (an extension of Ch 40). This lecture focuses on ..both of which maintain homeostasis in animals. Osmoregulation is the absorption and excretion of water and solutes so that the correct water balance (osmotic pressure = osmolarity = solute concentration in moles/L of solution) is maintained between the organism and its environment Marine fish are hypo-osmotic with their salt-water environment, so water is constantly lost by osmosis (higher lower H 2 O), and they: o drink water constantly, rarely urinate, and secrete accumulated salts out through their gills—all to try to keep up with water losses Freshwater fish are hyper-osmotic with their freshwater environment, so water constantly moves by osmosis into the fish, and they:
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o rarely drink, constantly urinate, and absorb salts through their gills—all to try to reduce water over- load Forms of nitrogenous waste (fig 44.10, p 875) Nitrogenous waste (ammonia, NH 3 which is toxic to animals) is formed by breakdown of protein and nucleic acids. Ammonia must be converted to non-toxic forms (and this requires ATP energy) by most animals. Ammonia is water-soluble, excreted as ammonium ions (NH 4 + ) directly into the water by most aquatic animals (fish) Urea is made in the vertebrate liver, water-soluble, requires less water than ammonia to excrete (and is less toxic). Urea is excreted by mammals, amphibians, sharks and some fish Uric acid is not as water-soluble as ammonia or urea, an
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This note was uploaded on 09/29/2011 for the course BIO 020.152 taught by Professor Pearlman during the Fall '08 term at Johns Hopkins.

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My_Ch44_lecture_rev09(2009050122141076) - Chapter 44:...

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