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Life in Water.docx

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BIOL 150
Ken Oakes

Life in Water 3.1 The Hydrologic cycle exchanges water among reservoirs - over 71% of earth is water - lakes, rivers(1%), oceans (97%) - polar ice caps and glaciers (2%) ‘reservoirs’: lakes, rivers, oceans, plus atmosphere, ice, organisms Evaporation Oceans 448 x 10 km 3 3 3 Continents 65 x 10 km /year Polar Ice (negligible) Precipitation Oceans 411 x 10 km /year Continents 100 x 10 km /year 3 3 Polar Ice ~2 x10 km /year - water enters each reservoirs as precipitation or as surface/subsurface flow - exits as evaporation/flow Hydrologic cycle powered by solar energy - drives winds and evaporates water. From surface of the oceans - water vapour cools as it rises from ocean’s surface and condenses (forming clouds) > clouds blown by solar-driven winds across planet > yield rain/snow (falls back to ocean and land) - falls on land: o immediately evaporates and re-enters the atmosphere o some contributes to icefields and glaciers o some consumed by terrestrial organisms o some percolates through soil and become groundwater o some ends up in lakes and ponds /streans and rivers >>>> sea - reservoirs replenished at diff rates: measure turnover times (time for the entire volume of a particular reservoir to be renewed) o size of reservoir and rates of water exchange  water in atmosphere: every 9 days  river water: 12 – 20 days  lake: days to centuries depending on depth, area, rate of drainage  oceans: 3,100 years 3.2 Life in wAter and the Natural History of Aquatic Environments The biology of aquatic environments corresponds broadly to variations in physical factors such as light, temperature, and water movements and to chemical factors such as salinity and oxygen - organisms need a lot of oxygen to undergo oxidative respiration - oxygen not gaseous but is dissolved in water - organisms extract oxygen (using gills), store oxygen for prolonged periods (marine mammals), or transport oxygen from above water surface to their tissues below (specialized roots of many plants) - challenges: o tendency of water to move along solute gradients can cause problems if internal solute concentrations differ from water outside o temp. regulation o light availability o access to nutrients and food The oceans - most extensive biome on earth Geography: - covers over 360 million km^2 of earth’s surface (70%) - one continuous, interconnected mass of water - Arctic (smallest and in north hem only), Atlantic, Indian, Pacific(largest), Southern - Oceanic circulation driven by prevailing winds and moderates earth’s climate (cold and warm water currents and streams) - - 5 major oceans
 - 1. Pacific: ~ 180 million km ; avg. depth > 4000 m o Marianas trench, deepest >10,000 m deep - - 2. Atlantic: ~ 106 million km2; avg. depth ~ 3500 m - 2 - 3. Indian:~73 million km ; avg.depth 3900m
 - 2 - 4. Southern: ~ 20 million km ; avg. depth 4500 m
 2 - 5. Arctic: ~ 14 million km ; avg. depth ~1000 m - Structure: - Littoral - Neritic - Oceanic: o Epipelagic o Mesopelagic o Bathypelagic o Abyssal zone o Hadal zone - benthic - LNEMBAH Light - 80% solar energy absorbed in first 10m(most UV and infrared) , all colors of the rainbow available to bounce off shallow reef fish o red, orange, yellow, green absorbed more rapidly than blue o diff from terrestrial: where chlorophyll absorbs blue and red light in photosynthesis, reflecting green light so plants appear green o ocean appears blue because the open ocean algae are at low concentrations and very little of blue light available is used - below 50/60m = blue twilight about 3,400m of deep black water receive no light unless produced by bioluminescent fishes and invertebrates - very little light penetrate deeper than 600m - marine organisms distributed according to conditions such as gradients of light, temp., surface and deep-water currents, salinity, oxygen, and nutrient/food availability Temperature - sunlight absorbed by water increases kinetic state/velocity of motion of water molecules - increased temp, increased kinetic state - more rapid molecular motion, decrease water density = warm water floats on cold water > surface water warmed by sun floats on colder water - warm and cold layers separated by a layer of water through which temp. changes rapidly with depth = thermocline - layering of water column by temp. – thermal stratification (perm. Feature) o temperate oceans stratified in summer. Thermocline breaks down as surface waters cool during fall and winter o high latitudes: thermal stratification weakly developed Water movements - oceans are never still - prevailing winds drive currents that transport nutrients, oxygen, and heat, even organisms o currents moderate climates, fertilize the surface waters off the continents, stimulate
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