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bieb132.lecture_3_sept_29

bieb132.lecture_3_sept_29 - Lecture 2 continued Most marine...

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Lecture 2 continued… Most marine organisms cannot regulate body temperature - But there are exceptions…
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Thermal regulation in marine mammals Maintain high body temperature with high metabolic rate (heat production), circulatory adaptations, and insulation (remember - breathe air!) FIG. 4.5 A model of a countercurrent heat exchanger. Warm fluid leaves the hot water bath and loses heat to the external environment, thus reducing the temperature toward the left. Because, however, the return flow gains heat by exchange with the adjacent outflow tube, some of the heat is recovered and returned to the heating chamber. FIG. 4.4 The pattern of veins (blue) wrapped around arteries in the flipper of a dolphin. This arrangement permits the venous blood to be warmed by heat transfer from arterial blood before it reenters the body core. (From Schmidt-Nielsen, 1975.)
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Countercurrent exchange conserves core heat in tuna (but no insulation) Minimize heat loss to periphery and at gills
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Temperature is only one of the parameters of the physical environmental that can challenge the adaptations of marine organisms for survival. Next consider salinity…
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If cells are moved to increased salinity…
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FIG. 4.12 (a) Osmosis: movement of pure water occurs across a membrane in the direction of higher solute concentration. (b) Change in the original body volume of the sipunculid Golfingia gouldii when transferred into diluted seawater at time = 0 hours.
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Osmotic pressure is the pressure that must be applied to a solvent to stop osmosis Pressure
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Isotonic – solutions with the same solute concentration as the cytosol Hypertonic – solutions having greater solute concentration than the cytosol Hypotonic – solutions having lesser solute concentration than the cytosol
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Important physical principles: A. van’t Hoff Equation for osmotic pressure ( π = C R T) π = osmotic pressure in atmospheres C = concentration in moles R = gas constant (0.082 liter-atmospheres/mole-degree) T = temperature ( o Kelvin) B. Fick’s Law of Diffusion (flux = Area x Diffusion coefficient x [ Δ concentration])
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What is the osmotic pressure (at 25°C) of seawater (compared to fresh water)? It contains approximately 27.0 grams of NaCl per liter. (Seawater contains other stuff, but we'll ignore it.) Convert grams to moles: 27.0 g ÷ 55.85 g/mol = 0.483 mol x 1.8 (When NaCl ionizes in solution it produces Na + ions and Cl¯ ions. One mole of NaCl produces 1 mole of each type of ion, so the molarity theoretically, equal to 2. But not all ionizes - use 1.8.) π (pressure) = (1.8) (0.483) (0.08206) (298) Answer: 21.5 atm. That's about 313 pounds per square inch Even 10% change in salinity results in pressures of > 30 psi (~auto tire pressure)
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Response to Environmental Change Conformer vs. Regulator What are the costs and benefits of the two types of response?
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Skin- largely impermeable to water Seawater= 1000mOsm
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