BRIC Outline

BRIC Outline - BRIC Outline BUs are affected by biological...

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BRIC Outline BU’s are affected by biological environment and physico-chemical environment. They don’t exist in isolation. Environmental conditions for the BU are constantly changing. Equilibrium is never reached. BU’s adapt to different environments. Life turns up everywhere, such as in anoxic underground pools of crude oil, in hot, sulfurous ocean vents, in brine pools five times saltier than the ocean, in places with toxic levels of heavy metals, acids, and radiation, in solid stone, and in the cold temperatures and high pressures under Antarctic ice. These aren’t typical, but they exist. Life can exist in harsh conditions. Ecology is the study of relationships between organisms and the environment. The same needs and responses are important even at widely differing BU levels. 6.1 BU Die Without Water 6.1.1 Water Has Unique Properties Water is denser as a liquid than a solid. Water has a high head capacity, or specific heat, meaning that it requires a large amount of heat to raise its temperature. This helps BU to maintain its thermal equilibrium despite sometimes rapid changes in environmental temperature. The strong hydrogen bonds in water explain why it has such high melting and boiling points. Water molecules roll rather than slide, giving water relatively low viscosity. This makes pumping water in BU’s much less energy intensive than it could be otherwise. 6.1.2 Water Surrounding BU BU are often surrounded by water. The brain for example is surrounded by a water based liquid.
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6.1.3 Water Balance Rate of water in - rate of water out + rate of water generated – rate of water consumed= rate of water storage. 6.1.4 BU Barriers to Water Movement Water can enter a BU due to a concentration difference (diffusion) or because of pumping (convection). Water can enter BU through the BU’s barrier, such as skin, but only a limited amount. If there is a disruption of the barrier, there can be life-threatening water balance problems. Surface lipids in the form of waxes have much to do with limiting drying rates to values below lethality. BU in an aquatic environment do not usually have such a barrier. As long as the osmotic concentration of solutes inside the BU is the same as the osmotic concentration of the solutes outside the BU, then a water balance can be maintained. If the surrounding fluid changes suddenly to a different solute concentration then the BU may not be able to survive. Water leaving a BU to a surrounding concentrated solution may cause dessication of the BU. Water entering a BU from a surrounding dilute solution can cause bursting. 6.2 BU Die Without the Right Amount of Oxygen Oxygen is needed for aerobic metabolism. 6.2.1 Anaerobes and Facultative Anaerobes All BU do not need oxygen. Anaerobic metabolism can proceed in the absence of oxygen to form intermediate products that can supply some of the energy needs of the BU. Anaerobic organisms cannot survive in the presence of oxygen. Those that can survive and function in either aerobic or anaerobic conditions are termed facultative (which actually means “adaptable”).
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6.2.2 Oxidative Metabolism
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This note was uploaded on 11/30/2009 for the course BIOE 120 taught by Professor Aranda-espinoza during the Spring '08 term at Maryland.

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BRIC Outline - BRIC Outline BUs are affected by biological...

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