Chap 3 PPT - CHAPTER 3 Water and the Fitness of the...

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Unformatted text preview: CHAPTER 3 Water and the Fitness of the Environment Three-quarters of the Earths surface is submerged in water The abundance of water is the main reason the Earth is habitable All living organisms require water more than any other substance Water is the biological medium on Earth Most cells are surrounded by water, and cells themselves are about 7095% water Water Content of the Body Water makes up 60% of adult body weight (higher for child) Body composition influences % water: of lean tissue weight is water of fat weight is from water Females and elderly have less water (less lean tissue) than men Water as an Essential Nutrient Carries nutrients and wastes Maintains the structure of large molecules Participates in metabolic reactions Solvent for minerals, vitamins, amino acids, glucose, and other small molecules Acts as a lubricant and cushion Aids in temperature regulation Maintains blood volume Polarity of water results in hydrogen bonding The water molecule is a polar molecule : The opposite ends have opposite charges Polarity allows water molecules to form hydrogen bonds with each other The hydrogen bonding is what contributes to the various properties water exhibits Animation: Water Structure Animation: Water Structure Hydrogen bond H + H O + + + Properties of water Four of waters properties that facilitate an environment for life are: Cohesive behavior Ability to moderate temperature Expansion upon freezing Versatility as a solvent Cohesion and Adhesion Collectively, hydrogen bonds hold water molecules together, a phenomenon called cohesion Cohesion helps the transport of water against gravity in plants Adhesion is an attraction between different substances, for example, between water and plant cell walls Animation: Water Transport Animation: Water Transport Water-conducting cells Adhesion Cohesion 150 m Direction of water movement Cohesion and surface tension Surface tension is a measure of how hard it is to break the surface of a liquid Surface tension is related to cohesion due to the water molecules adhering to each other. Moderation of Temperature Water absorbs heat from warmer air and releases stored heat to cooler air Water can absorb or release a large amount of heat with only a slight change in its own temperature Heat and Temperature Kinetic energy is the energy of motion Heat is a measure of the total amount of kinetic energy due to molecular motion Temperature measures the intensity of heat due to the average kinetic energy of molecules Celsius or Fahrenheit scale used The Celsius scale...
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Chap 3 PPT - CHAPTER 3 Water and the Fitness of the...

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