Chapter 44 - CR97-03-1

Chapter 44 - CR97-03-1 - Chapter 44 Chapter 44...

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Unformatted text preview: Chapter 44 Chapter 44 Osmoregulation and Excretion 1 of 20 of 20 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 44.1: Osmoregulation balances the uptake 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 • 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 • 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 44.2: An animal’s nitrogenous wastes reflect 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...
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This note was uploaded on 04/07/2008 for the course BIO 103 taught by Professor Mannino during the Fall '08 term at Long Island U..

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Chapter 44 - CR97-03-1 - Chapter 44 Chapter 44...

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