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Biogeochemical Cycles

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Presentation on theme: "Biogeochemical Cycles"— Presentation transcript:

1 Biogeochemical Cycles
Friedland: Chapter 3 (pgs ) Botkin: Chapter 6 (pgs )

2 Life and Chemical Elements
All living things are made of chemical elements and require: Micronutrients Macronutrients 24 elements required by all organisms Include the “Big Six”, which are the building blocks of life carbon oxygen hydrogen nitrogen phosphorus sulfur Micro - Elements required in small amounts by all life or moderate amounts by some forms of life


4 For life to persist elements must be available at the right time, in the right amount, and in right concentrations relative to one another Too much of some elements can be toxic Too little of some elements can limit growth and development – limiting factors These elements are continuously recycled throughout the atmosphere, biosphere, hydrosphere, and lithosphere, through the biogeochemical cycles

5 Geologic Cycles Tectonic Cycle
Creation and destruction of Earth’s outer layer (the lithosphere) About 100 km thick Broken into plates that float on denser material and move about 2-15 cm/year Plate tectonics has large scale effects Location and size of continents Alterations in climate (atmospheric and oceanic currents) Ecological islands (speciation and evolution) Areas of volcanic activity and earthquakes Plates move about as fast as finger nails grow


7 Plate boundaries Divergent
Occurs at a spreading ocean ridge, where plates moving away from one another New lithosphere produced Known as sea floor spreading, produces ocean basins

8 Convergent Occurs when plates collide
When heavier ocean plates meet lighter continental plates a subduction zone is present When two lighter continental plates collide a continental mountain range may form

9 Transform fault Occurs where one plate slides past another
San Andreas Fault in California Boundary of NA and Pacific plates LA moving towards SF

10 Rock Cycle Consists of numerous processes that produce rocks and soils Depends on the tectonic cycle for energy and the hydrologic cycle for water Rocks classified as Igneous – made from magma that cools at or near the surface (lave from volcanoes)

11 Sedimentary – weathered materials that accumulate in deposition basins, such as oceans, are compacted by overlying sediment layers (lithification)

12 Metamorphic – sedimentary rock buried at depths that are altered by heat, pressure, or chemically active fluids and transformed

13 Weathering Physical weathering is the mechanical breakdown (freeze, thaw) of rocks that produces sediment such as gravel, sand and silt Chemical weathering occurs when weak acids in water dissolve chemicals from rocks

14 Erosion Physical removal of rock fragments from a landscape or ecosystem Wind, water, ice transport and living organisms can erode materials

15 Rock Cycle Diagram (Botkin pg. 116)

16 The Hydrologic Cycle Transfer of water between the ocean, atmosphere and land Driven by solar energy Evaporation of water from oceans and land Precipitation of water on land Transpiration of water by plants Runoff from streams, rivers and subsurface

17 Hydrological Cycle Processes (p.67)
Showing the transfer of water (thousands km3/yr). It takes 1 water molecule 4,000 years to complete one cycle.

18 Total water on earth = 1.3 billion km3
97% in oceans 2% in glaciers and ice caps 0.001% in atmosphere The rest in fresh water on land At the regional and local level, the fundamental unit of the landscape is the drainage basin (watershed) The land area that contributes surface runoff to a particular stream or river Used to evaluate hydrology Vary greatly in size Usually named for main stream or river (e.g. Mississippi River) Hydrology = stream flow or runoff from slopes; important in assessing ecosystems research and conservation

19 The Carbon Cycle Carbon is the basic building block of life and the element that anchors all organic substances It is stored and transferred through the following processes: Photosynthesis Producers take in CO2 and incorporate it into their tissues Respiration All organisms release CO2 when they respire Decomposers return CO2 to the atmosphere when they break down dead organic material In what other form do organisms release carbon into the atmosphere? CH4

20 Large amounts of CO2 are exchanged between ocean and atmosphere
Some dissolved CO2 enters the food web via algae Some CO2 combines with calcium ions in the water to form CaCO3 (organism shells and sediment) Sedimentation and Burial CaCO3 can precipitate out of water and form limestone and dolomite rock via sedimentation Buried organic matter becomes fossilized over millions of years and can be transformed into fossil fuels 3. About CO2equal exchange (released by ocean and diffuses from atmosphere into ocean) 4. The amount of C removed form the food web by burial is about equal to the amount returned to the atmosphere through weathering of limestone and volcanic eruptions

21 Extraction Combustion
Humans remove C (in the form of fossil fuels) from the earth Combustion Burning fossil fuels for energy and wildfires release CO2

22 The Nitrogen Cycle Nitrogen is essential to life
Why? N2 makes up 78% of the Earth’s atmosphere Most organisms can’t use it directly Relatively unreactive element; must be converted to nitrate (NO3-) or ammonium (NH4+) = nitrogen fixation Performed by bacteria or abiotic processes: Cyanobacteria (blue-green algae) and bacteria that live on the roots of legumes (beans, peas, etc) use a specialized enzyme to break N2 bonds and add H+ ions to form NH3 (ammonia), which is converted to NO-3 in the soil N2 can also be fixed and converted into NO-3 by lightening and combustion, or by humans making fertilizers Humans now fix more N than nature

23 NO-3 and NH4+ can be used by producers to make proteins to build tissues, which can in turn be eaten by consumers = assimilation When organisms create nitrogen-containing waste or die, decomposers feed on the organic material and create NH4+ = ammonification Nitrifying bacteria in the soil then convert NH4+ into nitrite (NO-2), then into NO-3 = nitrification Denitrifying bacteria convert NO-3 into N2 gas that returns to the atmosphere

24 Nitrogen Cycle (pg. 70)

25 The Phosphorous Cycle P is a major component of DNA, RNA and ATP
Phosphorous cycles between rocks, soil, ocean sediments, and living organisms Does not enter the atmosphere Low solubility in water; much of it precipitates out of solution forming phosphate (PO43-) sediment on ocean floors On land, the major source of P is the weathering of rocks Added to fertilizer. We mine ocean floors for P

26 Phosphorus Cycle (pg. 72)

27 The Sulfur Cycle Sulfur is a component of proteins and allows organisms to use oxygen Most S exists in rocks and is released into soil and water through weathering Plants absorb sulfur through their roots in the form of sulfate (SO42-) Volcanic eruptions release sulfur dioxide (SO2), which mixes with water in the atmosphere to form sulfuric acid (H2SO4) , then falls to the ground as precipitation

28 Cycle Diagrams Visually represent cycles as systems using box-and-arrow diagrams (pg. 112) Flow is the amount of substance moving from one compartment to another Flux is the rate of transfer Residence time is the average time the substance is stored in a compartment The donating compartment is the source, the receiving compartment is the sink

29 Group Project (all cycles except Rock and Tectonic)
You and your lab partner are to answer the following: How/why is each cycle important to organisms? Discuss specific human actions that affect/influence each cycle (except geologic) and the consequences of those actions Identify which cycles have limiting factors. How do they affect the cycle and ecosystems?

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