Chapter 4 Water(1) Updated (19) copy.pptx
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* Chapter 4 Water * 4.1 Water: Simple Facts *Over 71% of the earth’s surface is covered by water. *The water on the earth’s surface is unevenly distributed among aquatic environment. *Oceans contain over 97% of the water in the biosphere. *Additional 2% for the polar ice caps and glaciers....
* Chapter 4 Water * 4.1 Water: Simple Facts *Over 71% of the earth’s surface is covered by water. *The water on the earth’s surface is unevenly distributed among aquatic environment. *Oceans contain over 97% of the water in the biosphere. *Additional 2% for the polar ice caps and glaciers. *Water: Simple Facts *Less than 1% is freshwater in rivers, lakes. So most is seawater. *The distribution of water is not static. *Why….??? think…. *Because of the dynamic exchange (Hydrologic cycle). What is a reservoir? *Is a place where water is stored for some period of time, this water in reservoir is renewed or turned over……. How?????? 4. 2 Hydrological Cycle *Exchanges water among reservoirs *Is powered by solar energy, which drives the winds and evaporates water, primary from the surface of the oceans. * Hydrological Cycle 1. see below… Water vapor water vapor cools and condense Forming clouds, are blown by winds Yielding rain or snow (majority falls back on the oceans and some falls on land Water falls on land has several fates: some Evaporate and re-enter the atmosphere Consume by organisms Some percolate through the soil and become groundwater In lakes ponds, rivers, and stream and eventually to the sea *4.3 The Concepts *The movement of water down concentration gradients in terrestrial and aquatic environments determine the availability of water to organisms. *Concentration Gradient is the difference in concentration of a substance from one area to another. *Evaporation * *On land, evaporation accounts for much of water lost by organisms. *The evaporative water loss depends upon: * *(1)temperature and (2)water content of the air around the organism. *Evaporation *As the amount of water vapor in the surrounding air increases, the water concentration gradient from organisms to the air is reduced and the rate at which organisms lose water to the atmosphere decrease. * 4.4 Water Movement in Aquatic Environments *If the internal environment of the organism and the external environment differ in concentration of water and salts….. * These substances will tend to move down their concentration gradients. This movement is the process of diffusion. *Osmosis is the diffusion of water through a selectively permeable membrane from an area of high water potential (low solute concentration) to and area of low water potential (high solute concentration). *Water Movement * Isosmotic: Solutions of equal solute concentrations . *Hypoosmotic: Solution with a lesser concentration of solute ( fresh water compared to salt water). If a cell from a fresh water fish is placed into a beaker of salt water, the cell is said to be hypoosmotic to the water *Hyperosmotic: Solution with the greater concentration of solute ( salt water compared to fresh water). If a cell from a salt water fish is placed in a beaker of fresh water, the cell is said to be hyperosmotic to the water. * 4.5 Water regulation on land *Terrestrial plants and animals regulate their internal water by….. *balancing water acquisition against water loss. *When organisms moved into the terrestrial environment they faced two major environmental challenges: *1. massive losses of water to the environment through evaporation and *2. reduced access to replacement water. * 4.6 Water regulation by terrestrial animals *Wia=Wd+Wf+Wa-We-Ws *Wia= internal water of an animal results from a balance between water acquisition and water loss. *The major source of water are: *Wd= water taken by drinking *Wf=water taken with food *Wa= water absorbed from the air *The avenues of water loss are: *We= water lost by evaporation *Ws=water lost with various secretions and excretions including urine, mucus, and feces. * 4.7 Water regulation by Terrestrial Plants *Summary of water regulation by terrestrial plants: * Wip=Wr+Wa-Wt-Ws *Wip= The internal water conc. of a plant results from a balance between gain and losses, where the major sources of water for plant are: * Wr=water taken from soil by roots *Wa= water absorbed from the air *The major ways that plants lose water are, *Wt=water lost by transpiration *Ws=water lost with various secretions and reproductive structures including nectar, fruit, and seeds. * 4.8 Water Acquisition by Animals *1. Many small terrestrial animals can absorb water from the air. *2. Most animals get their need for water either by drinking or taking in water with food. *3. Desert animals e.g beetle in the genus Lepidochora digs trenches on the face of the sand dunes to condense and concentrate fog. *4. Onymacris beetle takes in water with its food. The remaining water is produced when the beetle metabolizes the carbohydrates, proteins, and fats in its food. * Camels and Saguaro Cactus Approaches to Desert * Both acquire massive amounts LIFE of water when water is available, store water, and conserve water. *A Camel can walk in desert 6 to 8 days without drinking. The water stored in its tissues. *A Camel faces into the sun, reducing the body surface it exposes to direct sunlight also its thick hair insulates it from the intense desert sun. When it rains camels take in massive quantities of water. *A camel does not store water in its hump but fat, which is source of metabolic water *The Saguaro takes a similar approach to camels: *The saguaro cactusCactus *1. Water is stored in the massive trunk and arms *2. Take in massive quantities of water. *3. Keep the stomata closed during the day when transpiration losses would be highest. *4. Covered by spines(reduce the heat gain). *5. Exposing only tops of its trunk and branches to midday sun. * 4.9 Water and Salt Balance in Aquatic Environment *Wi=Wd-Ws±Wo *Wi Internal water concentration *Wd drinking water *Ws=Secretion water with urine *Wo= by osmosis, an aquatic organism may either gain or lose water depending on the organism and environment * Water and Salt Balance in Aquatic Environment *Freshwater fish face a challenge , they are hyperosmotic, they have body fluids that contain more salt and less water than the surrounding medium. Therefore: *1) Water diffuses inside through their gills. *2) Fresh water fish takes salt with foods. *3) Specialized cells in the gills actively absorb Cl from surrounding water and Na follows. *4) Fish excrete excess internal water as large quantities of dilute urine. * Water and Salt Balance in Aquatic most marine invertebrates and * In contrast toEnvironment sharks, marine bony fish have body fluids that are strongly hypoosmotic to the surrounding medium. Therefore: *1) They lose water to the surrounding seawater across their gills. *2) Marine bony fish make up these water losses by drinking seawater. 3) Specialized "chloride" cells at the base of their gills secrete sodium and chloride directly to the surrounding seawater.
