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What IS a “biogeochemical cycle”? BIO = “life” GEO = “earth” CHEMICAL = “elements – C, O, N, P, S• a cycling of nutrients (water, carbon, oxygen,nitrogen, phosphorus, sulphur) from the abioticcomponents of the ecosystem (water, air, soil,rock) through the biotic components (plants,animals, fungi, bacteria)
Two Secrets of Survival: Energy Flows and Matter Cycles An ecosystem survives by a combination of energy flow (from Sun to Earth) and matter cycling. Remember: the Earth is a CLOSED system Figure 3-14
THE HYDROLOGIC (WATER) CYCLE Rain clouds Condensation Transpiration Evaporation Precipitation Transpiration to land from plantsPrecipitation Precipitation Evaporation Surface runoff from land Evaporation Runoff from ocean Precipitation (rapid) to oceanInfiltration and SurfacePercolation runoff (rapid) Groundwater movement (slow) Ocean storage Fig. 3-26, p. 72
Effects of Human Activities on Water Cycle We alter the water cycle by: Withdrawing large amounts of freshwater. Clearing vegetation and eroding soils. Polluting surface and underground water. Contributing to climate change.
Effects of Human Activities on Carbon Cycle We alter the carbon cycle by adding excess CO2 to the atmosphere through: Burning fossil fuels. Clearing vegetation faster than it is replaced photosynthesis = CO2 Figure 3-28
Effects of Human Activities on the Nitrogen Cycle We alter the nitrogen cycle by: Adding nitrous oxide to the atmosphere from vehicles and factories which contributes to acid rain. Contaminating ground water from nitrate ions in inorganic fertilizers. Releasing nitrogen into the troposphere through deforestation (less N assimilated by trees).
THE PHOSPHORUS CYCLE mining Fertilizerexcretion Guano agriculture uptake by weathering uptake by autotrophs autotrophs Marine Dissolved leaching, runoff Dissolved Land Food in Ocean in Soil Water, Food Webs Water Lakes, Rivers Webs death, death, decomposition decompositionsedimentation settling out weathering uplifting over geologic time Marine Sediments Rocks Fig. 3-31, p. 77
Effects of Human Activities on the Phosphorous Cycle We remove large amounts of phosphate from the earth to make fertilizer. We reduce phosphorous in tropical soils by clearing forests. We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers – excess phosphorus causes algal blooms
Assignment: Put the 4 cycles together on one poster! Draw the hydrologic, carbon, nitrogen, phosporus and cycles onto one piece of poster paper. Include the required terminology Follow the criteria on the rubric provided Assessment will be done by performance (explanation of the cycles by the group)