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Published byGiles Hoover Modified over 8 years ago
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QUICK WRITE: 3-5 mins As Soon As You’re Seated Relate the images to the Nitrogen Cycle Remember the 4 Players
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THINK... Chlorophyll is a protein. CONNECT... Nitrogen Levels
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From the Garden... Gardeners often aerate (expose to oxygen) their soil in early spring. Why?
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Exposing the denitrifying bacteria to oxygen reduces the breakdown of nitrates into nitrogen gas. Nitrates will then remain in the soil where they can be drawn in by grass roots and used to make proteins.
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Fertilizers Harvesting crops = nitrogen loss (doesn’t return) Farmers must replace missing nutrients or the soil will be depleted. Fertilizers are materials used to restore nutrients and increase production from land. Some estimates suggest that nitrogen fertilizers can double yields of cereal crops.
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Fertilizers Cont’d High levels of nitrate = high levels of nitric acid Affects all organisms, including decomposer bacteria 6-9 kg/ha per year for ten years produces soil that is 10 times as acidic.
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Algal Blooms Spring runoff carries decaying plant matter and fertilizer-rich soil to streams. Nutrients allow algae in water to grow rapidly. When this “algal bloom” dies, bacteria use oxygen from the water to decompose them. Oxygen levels in lakes drop quickly, so fish and other animals may begin to die.
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Dying animals worsen the problem because decomposers begin to recycle the matter from the dead fish. This allows the population of bacteria to grow even larger, and use still more oxygen.
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THE PHOSPHORUS CYCLE
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Key Element in… Cell Membranes ATP (where did we hear this before?) Making of DNA Calcium Phosphate of bones TWO PARTS: Long Term Cycle (Earth’s Crust) Short Term Cycle (Living Organisms)
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LONG TERM CYCLE P is found in bedrock in the form of phosphate ions (PO 4 ). Phosphates are soluble in water, so can be dissolved out of rock. While dissolved, phosphates can be absorbed by photosynthetic organism, and thus pass into food chains.
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Phosphates eroded by rock are also carried by water from land to rivers, and then to oceans. In the ocean, phosphates are absorbed by algae and other marine plants, where they then enter food chains.
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Marine animals use phosphates to make bones and shells. When they die, these hard remains form deposits on the ocean floor. Covered with sediment, the deposits eventually become rock, ready to be brought to the surface again. MILLIONS OF YEARS!!!
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SHORT TERM CYCLE Wastes from living things are recycle by decomposers. Decomposers break down wastes and dead tissue, releasing phosphates. Cycle is much more rapid
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