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Daily question

Daily question. Use the second law of thermodynamics to explain why there is such a sharp decrease in usable energy as energy flows through a food chain. Does an energy loss at each step violate the first law of thermodynamics?

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Daily question

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  1. Daily question • Use the second law of thermodynamics to explain why there is such a sharp decrease in usable energy as energy flows through a food chain. Does an energy loss at each step violate the first law of thermodynamics? • 1st law: Energy is neither created nor destroyed, but may be converted from one form to another • 2nd law: When energy is changed from one form to another, some useful energy is degraded to lower quality, more dispersed, less useful energy

  2. Cycles, watersheds and ecosystem ecology

  3. Energy flows,matter cycles • Energy enters ecosystems in 2 ways: • Sun • Chemosynthetic bacteria at hydrothermal vents • Most deep sea ecosystems depend on photosynthesis: how? • Some: chemosynthetic bacteria

  4. Energy flow • Result of flow—and loss—of energy at each trophic level is the ecological pyramid • Numbers • Biomass • Especially: Energy

  5. Under what conditions would the pyramid of numbers not strictly be a pyramid? ie. Give an example Trees are few and large, insects many and small Trees and insect herbiroves Problem

  6. Matter • Earth is open system with respect to energy • Mostlyclosed system regarding matter • Elements cycle

  7. Involve biological, geological, and chemical interactions Matter not created 5 cycles representative of all biogeochemical cycles: Carbon Nitrogen Phosphorus Sulfur Water Biogeochemical cycles

  8. Essential questions • How do elements important to life move through the biosphere and geosphere? (this is called ``flux’’) • Where are these elements stored for long term? (places are called ``sinks’’) • How are humans altering these cycles? (``anthropogenic effects’’)

  9. Hydrologic cycle • Water you drink today may have been part of a dinosaur’s urine 75 million years ago. • OR, in the Passaic River 4 months ago •  residence times • Range from days in the atmosphere to thousands of years deep in the ground

  10. Where is the water?

  11. http://ga.water.usgs.gov/edu/watercycle.html

  12. Sources vs. sinks • Reservoir = where in the environment (atmosphere, hydrosphere, geosphere, biosphere) that an element can be found • Sink = Flow into reservoir is greater than flow out. • Source = Flow out of reservoir is greater than flow in. FLUX SINK SOURCE

  13. Reservoirs? Sedimentary rocks Oceans Atmosphere Fossil fuels Sinks: oceans, atmosphere Source: fossil fuels Carbon cycle

  14. Carbon cycle • C found in molecules essential to life (proteins, carbohydrates, etc) • Organic chemistry is the chemistry of C • Atmosphere: CO2 • Ocean: dissolved carbon dioxide, dissolved organic C • Earth: • *Sedimentary rocks (ie, limestone) • *Fossil fuels * The major reservoirs

  15. Carbon cycle • How does C go from atmosphere to biosphere? _____________ • What are various pathways that C can take once in the biosphere? • How does C go from geosphere/biosphere back to atmosphere? _____________ • Residence times: How long does C remain in reservoirs?

  16. Carbon cycle measurement

  17. Nitrogen cycle

  18. How read this graph?

  19. Nitrogen cycle • N essential to life: Found in proteins and nucleic acids. • Where is most nitrogen?_____________ • N2 is so stable, doesn’t readily combine with other atoms

  20. Nitrogen cycle • 5 main steps: • Nitrogen fixation • Nitrification • Assimilation • Ammonification • Denitrification • Bacteria involved in all steps except assimilation

  21. Nitrogen fixation N2  NH4+ • Conversion of gaseous nitrogen (N2) to ammonia (NH4+) • Fixed means, ``put into a form organisms can use.’’ • Combustion, volcanic action, lightning, industrial processes all fix N • Bacteria fix N anaerobically. • Some found inside root nodules, Rhizobium

  22. Nitrification NH4+ NO3- • Conversion of ammonia or ammonium to nitrate (NO3-) • Soil bacteria • Bacteria get energy

  23. Assimilation • Plant roots absorb nitrate, ammonia, or ammonium and assimilate the nitrogen into plant amino acids and nucleic acids • Animals that consume plants then assimilate the nitrogen into their bodies

  24. Ammonification • Conversion of biological nitrogen compounds (what are these?) back into ammonia and ammonium ions. DECOMPOSITION • Step 1: organisms produce nitrogen-rich waste • Step 2: bacteria (decomposers) convert waste into simpler nitrogen-containing molecules (NH3, NH4+)

  25. Denitrification • Bacteria reverse the action of nitrogen-fixing bacteria • Nitrogen released back to atmosphere

  26. Watersheds and the cycles • Watershed = area of land that drains into a body of water

  27. Earth’s water in dynamic equilibrium IF: Precipitation to ocean = 385,000 km2/yr Evaporation from ocean = 425,000 km2/yr What is a good estimate for runoff to ocean? 40,000 km3/yr PROBLEM

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