BIOL 152 1st Edition Lecture 23 Outline of Last Lecture - Circulation Outline of Current Lecture - Osmoregulation Current Lecture- Osmoregulation Osmoregulation and Excretion- Homeostasiso Concentrations of blood solutes maintained within narrow limitso ‘Threats’ posed to o Freshwater fish – environment diluting body fluidso Marine/desert animals – environment depleting body fluids- Two key homeostatic processes1. Osmoregulation– controlled movement of solutes between external environment and internal fluids. Water follows solutes via osmosis.2. Excretion – disposal of N-containing wastes- Why osmoregulation?o Electrolyte balance is essential for cellular processes, and life itselfo NaCl: compound that dissociates into ions when dissolved in water. o Cells require precise concentrations of electrolytes to function normally- Osmolarity (mosm/L)- Isotonic/isosmotic – water balance - Hypertonic/hyperosmotic – water goes out- Hypotonic/hypoosmotic – water goes in - Osmoconformer – isosmotic to the environment These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Osmoregulation – internally regulate isosmotic conditions independent of its environment - 5% of our BMR, 30% for brine shrimp in Salt Lake- Stenohaline – cannot tolerate changes in environment - Euryhaline – can survive large fluctuations in environment o Saltwater fisho Freshwater fish- Osmoregulation in Terrestrial animalso Lose water: Gas exchange, excretion, and through skino Adaptations to minimize water loss: o Waxy outer layers, shells, layers of dead keratinized cells, nocturnal habit, internal gas exchange, kidneyso Gain water: water intake, metabolism, food- Nitrogenous Wasteso Metabolic wastes from proteins and nucleic acidso Must be dissolved in watero Ammonia – remove nitrogen in this form, need a lot of water for intake so mainly done by aquatic species o Urea – mammals, sharks adult amphibians. product of combining ammonia and carbon dioxide, produced in livero Uric acid – birds reptiles snails. Mix of feces and water. Release of nitrogenous waste. Forlittle access to water- Evolution and Nitrogenous Wastes1. Mode of Reproduction – solubility of waste2. Habitat – aquatic versus terrestrial and dry versus wet conditions.- Key steps in excretion of filtrate1. Excretory tubule collects filtrate from blood.2. Transport epithelium reabsorbs substances from filtrate.3. Toxins and other wastes are extracted from body fluid into excretory tubule.4. The filtrate leaves the body.- Kidneys make up _.5_% of body weight, yet receive _25_% of cardiac output- EVERY DAY:o 1100-2000 L of blood moves through kidneyso 180 L of filtrate is collected o 99% of water, sugars, vitamins, organic nutrients are reabsorbedo Leaving 1.5 L of
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