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Chapter 44 - CR97-03-1

Chapter 44 - CR97-03-1 - Chapter 44 Osmoregulation and...

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Chapter 44 Chapter 44 Osmoregulation and Excretion 1 of 20 of 20
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Overview: A balancing act 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 Osmoregulation regulates solute concentrations and balances the gain and loss of water Excretion gets rid of metabolic wastes 2 of 20 of 20
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44.1: Osmoregulation balances the uptake and loss of water and solutes 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 Water uptake and loss are balanced by various mechanisms of osmoregulation in different environments Osmoconformers are marine animals that are isoosmotic with their surroundings and do not regulate their osmolarity Osmoregulators expend energy to control water uptake and loss while living in either hyperosmotic or hypoosmotic environments 3 of 20 of 20
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Most animals are said to be stenohaline They cannot tolerate substantial changes in external osmolarity Euryhaline animals can survive large fluctuations in external osmolarity 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 Freshwater animals constantly take in water from their hypoosmotic environment They lose salts by diffusion 4 of 20 of 20
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Freshwater animals maintain water balance by excreting large amounts of dilute urine Salts lost by diffusion are replaced by foods and uptake across the gills Some aquatic invertebrates living in temporary ponds can lose almost all their body water and survive in a dormant state This adaptation is called anhydrobiosis Land animals manage their water budgets by drinking and eating moist foods and by using metabolic water Transport epithelia are specialized cells that regulate solute movement Essential components of osmotic regulation and metabolic waste disposal Arranged into complex tubular networks Example: The salt glands of marine birds, which remove excess sodium chloride from the blood (Fig 44.7) 5 of 20 of 20
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44.2: An animal’s nitrogenous wastes reflect its phylogeny and habitat its phylogeny and habitat The type and quantity of an animal’s waste products may have a large impact on its water balance Among the most important wastes are the nitrogenous breakdown products of proteins and nucleic acids
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