Chapter 3 Water and the Fitness of the Environment

Chapter 3 Water and the Fitness of the Environment -...

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Unformatted text preview: Chapter 3 Water and the Fitness of the Environment Overview: The Molecule That Supports All of Life Water is the biological medium on Earth All living organisms require water more than any other substance Most cells are surrounded by water, and cells themselves are about 7095% water Water is found in all three states naturally The abundance of water is the main reason the Earth is habitable Waters emergent properties Understanding lower levels of organization leads to new properties at higher levels. Concept 3.1: The polarity of water molecules 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 Short lived At 37C 15% are H-bond Concept 3.2: Four emergent properties of water contribute to Earths fitness for life Four of waters properties that facilitate an environment for life are: Cohesive behavior Ability to moderate temperature Expansion upon freezing Versatility as a solvent #1 Cohesion Water molecules stay close to one another because of hydrogen bonding Happens in all forms (solid, liquid, gas) H-bonds are fragile (1/20), but collectively strong Cohesion Collectively, hydrogen bonds hold water molecules together, a phenomenon called cohesion Cohesion helps the transport of water against gravity in plants Evaporation as water evaporates, more water is pulled up Adhesion is an attraction between different substances, for example, between water and plant cell walls Surface tension is a measure of how hard it is to break the surface of a liquid Surface tension is related to cohesion The surface of water is an organized arrangement of water molecules that are H-bonded to the molecules below and the water below An invisible film Water striders Full glass of water #2 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 As the average speed of molecules increases we see a increase in the temperature Ex: A swimmer in the ocean has higher temperature than the water, but the ocean has more heat because of its volume....
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Chapter 3 Water and the Fitness of the Environment -...

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