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Jason ShahAP BiologyPeriod #2AP Biology Test Review Guide:Ecology:Chapter 28:A. The Water Cycle•Animals lose water through sweat, feces, urine, breath•H2O molecules do not break or split.1. The Path of Free Water•Water evaporates from the oceans into the atmosphere•Moisture from plants reaches the atmosphere through transpiration•Most precipitation falls into the ocean but the rest is held in bodies of fresh water•Only 2% of the earth’s water is captured2. The Importance of Water to Organisms•Ability to capture water decides life or death•Plants get the water from the earth•Animals get water directly or from plants and animals they eat•Amount of free water relates to abundance of life3. Groundwater•Found in aquifers: permeable, saturated, underground layers of rock, sand, and gravel.•Water table: the unconfined upper portion of groundwater which flows into streams and is accessible by plants.•Recharged by precipitation and water seeping down from lakes, rivers, etc.•Problems are appearing where humans are overusing the aquifers, and they are not able to replenish themselves.•Also a problem with chemical pollution in groundwater from pesticides and herbicides, and also dumping chemical waste in ponds and lagoons.4. Breaking the Water Cycle•In forest ecosystems plants absorb the water and then transpire it back into the air where it is then returned as rainfall.
•However, due to deforestation, such forest ecosystems have had their water cycle ruined because not enough water is transpired back to cause precipitation; instead it is drained away to the sea.•The process/damage is extremely hard if not impossible to reverse or fix.B. The Carbon Cycle•Cycle based on carbon dioxide•Plants use photosynthesis to capture the carbon•Respiration returns the carbon dioxide to the atmosphere•Fossil Fuels also contain carbon and burning them releases carbon dioxide•Due to the recent increase in burning fossil fuels, the carbon dioxide levels have risen and continue to rise.•Thus, the balance between photosynthesis and respiration has been shifted and we can see the effects already through global warming.•Fixed carbon compound plus oxygen yields carbon dioxide and water through a combustion reaction.C. The Nitrogen Cycle•Bacteria•Can convert atmosphere nitrogen into forms that can be used for biological processes•Very stable (3x bond)•Nitrogen Fixation: N2BH2 2NH3•Some bacteria form symbiotic relationships with plants•Only symbiotic produce significant amounts of nitrogen•