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K._Water_blank - Principles of Biology II Osmoregulation...

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Principles of Biology II Osmoregulation and Excretion This lecture will cover Chapter 44. Read the chapter quickly before coming to class. Become familiar with the following parts of the nephron and their abbreviations; also be able to trace the movement of materials through these parts from the blood to outside the body. Bowman’s capsule (BC) Collecting duct (CD) Distal tubule = distal convoluted tubule (DCT) Loop of Henle (LH): ascending limb Loop of Henle (LH): descending limb Proximal tubule = proximal convoluted tubule (PCT) Osmoregulation and Excretion Chapter 44 • Regulation of internal environment – Water (by controlling solute concentrations) – Ions (including H+) – Wastes • Organs – Kidneys and kidney like organs in nephridia – Epithelial tissues: skin, gills, digestive tract I. Wastes • Most important: nitrogenous – From breakdown of proteins and amion acids – More produced by endotherms • Three forms – Ammonia • Highly toxic, highly water soluble • Most aquatic organisms • Synthesis does not need much energy
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– Urea • Less toxic, can be stored at higher concentrations • Less water needed to remove • Requires energy to produce • Mammals (event aquatic mammals), terrestrial amphibians, and sharks – Uric acid • Non-toxic, but not water soluble • Little water needed to remove • Requires much energy to produce • Birds, most reptiles (related to shelled egg) • Bird poop the white stuff is uric acid. • It can be made and set aside and wont affect the embryo – Wastes can vary with environment II. Water • Roles: chemical reactions, solvent, bulk flow, temperature control • Control: exchange with environment – Enters body: food, drink, skin, gills – Leaves body: urine, feces, skin, gills, evaporation (skin, lungs, airways, mouth) • Moves across cell membranes by diffusion (osmosis: depends on solute concentrations) – NO active transport Strategies 1. Osmoconformers • Most marine invertebrates • Do not control water exchange – Composition of internal environment is the similar to the external
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K._Water_blank - Principles of Biology II Osmoregulation...

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