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Intro to Biogeochemical Cycles.
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Intro to Biogeochemical Cycles Biogeochemical cycles are any of the natural circulation pathways of the essential elements of living matter. These elements in various forms flow from the nonliving (abiotic) to the living (biotic) components of the biosphere and back to the nonliving again. In order for the living components of a major ecosystem (e.g., a lake or forest) to survive, all the chemical elements that make up living cells must be recycled continuously.
Connections: Matter Cycling in Ecosystems The relationship between the Abiotic and Biotic • Biogeochemical cycles • Global recycling systems that interconnect all organisms. • Nutrient atoms, ions, and molecules continuously cycle between • air, water, rock, soil, and living organisms. • Nitrogen cycle Carbon cycle Hydrologic cycle (H2O) Phosphorus cycle http://www.youtube.com/watch?v=leHy-Y_8nRs
Intro to Carbon and Water Cycles • http://www.youtube.com/watch?v=2D7hZpIYlCA
Hydrologic (Water) Cycle Significance The water/hydrologic cycle collects, purifies, and distributes the earth’s water in a vast global cycle. Water is the primary sculptor of the earth’s landscape. Water is the major form of transportingnutrients within and between ecosystems.
The water cycle is altered by man’s activities: • We withdraw large quantities of freshwater. • We clear vegetation and increase runoff, reduce filtering, and increase flooding. • We add nutrients like fertilizers and modify the quality of the water. • The earth’s water cycle may be speeding up due to a warmer climate. This could change global precipitation patterns and may intensify global warming (water vapor increases in the troposphere).
The Carbon Cycle Carbon moves through water and land systems, using processes that change carbon from one form to another. • CO2 gas is an important temperature regulator on Earth. • Photosynthesis in producers and aerobic respiration in consumers, producers, and decomposers circulates carbon in the biosphere. • Fossil fuels contain carbon; in a few hundred years, we have almost depleted such fuels that have taken millions of years to form. • Carbon recycles through the oceans. Oceans act as a carbon sink, but when warming occurs, they release carbon dioxide.
The carbon cycle is altered by man’s activities: • Excess carbon dioxide being added to the atmosphere through our use of fossil fuels and our destruction of the world’s photosynthesizing vegetation has contributed to global warming. The natural greenhouse effect is being strengthened by increasing temperatures.
The Nitrogen Cycle The nitrogen cycle converts nitrogen (N2) into compounds that are useful nutrients for plants and animals. • The nitrogen cycle includes these steps: • Nitrogen Fixation: Specialized bacteria convert gaseous nitrogen to ammonia (NH4) • Nitrification: Special bacteria convert ammonia (NH4) in the soil to nitrite ions and nitrate ions; the latter is used by plants as a nutrient. • Ammonification: Decomposer bacteria convert detritus (waste) into ammonia and water-soluble salts • Denitofication: nitrogen leaves the soil. Anaerobic bacteria in soggy soil and bottom sediments of water areas convert NH3 and NH4+ back into nitrite and nitrate ions; then nitrogen gas and nitrous oxide gas are released into the atmosphere.
The nitrogen cycle is altered by man’s activities: • In burning fuel, we add nitric oxide into the atmosphere. It can be converted to NO2 gas and nitric acid, and it can return to the earth’s surface as acid rain. • Nitrous oxide that comes from livestock, wastes, and inorganic fertilizers we use on the soil can warm the atmosphere and deplete the ozone layer. • We pollute aquatic ecosystems with agricultural runoff and human sewage. • We remove nitrogen from topsoil with our harvesting, irrigating, and land-clearing practices.
Nitrogen Cycle Activity • You will become an atom of Nitrogen • As an atom of Nitrogen, you will travel through the Nitrogen Cycle (different reservoirs) based on the roll of a dice. • You will carry a passport with you as you travel. Your passport must be stamped at each destination before you can travel to the next. • Be sure to note on your passport how you got from one place to the next based on your dice roll.
Activity Discussion Questions • How many stops can you make on your trip? • Will your journey ever end? • Was everyone’s journey the same? Why/Why not? • What would happen if a farmer used too much fertilizer (meaning in the game everyone would start at the fertilizer station at the same time)? • What would happen if we burnt too many fossil fuels? • Livestock farming creates a large amount of animal waste. How would this affect the nitrogen cycle?
The Phosphorus Cycle • We need to use phosphorus-based fertilizers because the phosphorus cycle is much slower in moving through the earth’s water, soil, and organisms and is often the limiting factor for plant growth. • Phosphorus washes from the land, ending up in the ocean where it may stay for millions of years. • Phosphorus also limits growth of producers in freshwater streams and lakes due to low solubility in water.
The phosphorus cycle is altered by man’s activities: • We mine phosphate rock to produce fertilizers and detergents. • We cut down tropical forests and, thereby, reduce the phosphorus in tropical soils. • We compromise aquatic systems with animal waste runoff and human sewage.
Carbon Cycle Activity • Sort game cards by heading and pick a game piece • Place game pieces at vegetation • Roll the dice to see who starts. Player with the highest number starts first and the game rotates clockwise • Begin by picking a vegetation card. Read the card to find out your next destination and then roll the dice to find out how many spaces you move towards your destination. Record the appropriate info from each card to your worksheet. • Once you reach your destination, draw a card matching that destination and record the info. Continue to roll the dice to determine how many spaces you will move. • The first person back to vegetation, Wins!
