Biogeochemical Cycles and Energy Flow biogeochemical - bio (living organisms); geo (environment:

1. Biogeochemical Cycles and Energy Flow • biogeochemical - bio (living organisms); geo (environment: • soil, water, air) • nutrient cycles - cycles of elements essential to the growth • of living organisms • essential to plants - C, H, O, P, K, I, N, S, Ca, Fe, Mg, Cl, Cu, • B, Mn, Zn, Mo • - essential to animals - same except B; also Se, Co, F, Cr, Si • - why study cycles? important to understanding ecosystem • function • 4 important cycles - N, CO2, S, and H20 • N, p 31 • N is the primary element for amino acid production (protein) • N2 is an inert gas in the atmosphere and unusable to plants • in this form; air is about 80% N • N fixation - conversion of inert N2 to NH3 (ammonia), nitrites • (NO2), or nitrates (NO3)

2. some plants (legumes: Family Fabaceae includes beans, • peas, peanuts) and symbiotic (interacting species that are • closely or completely dependent on each other) bacteria in • root nodules (bacteria clusters) fix N to NH3 making it free to • plants and animals • other free-living aerobic bacteria in soil and blue-green algae • in aquatic systems serve the same purpose • bacteria make NH3 by splitting N2 and combing it with H • (very high biological energetic costs) • non-biological fixation - lightning (chemical reaction) and • volcanoes (by emission) produce NO3 • other changes to N - bacteria convert NH3 to NO2 and NO2 • to NO3; denitrifying bacteria in anaerobic conditions convert • above molecules to N2 that goes back to the atmosphere

4. amount of daily fixation and release of N is roughly equal • C, p 32 • all life on earth is carbon based; all living tissue contains C • C cycle is important for possible role in global warming • CO2 required by plants for photosynthesis; very small • amount in atmosphere (0.03%) but very important • CO2 is produced by plants and animals thru cellular • respiration (cell activities) • dynamic equilibrium among C forms in water (bicarbonates, • carbonates), sediments and fossil fuels (oil, natural gas, • coal), atmosphere, plants, and soils

8. S, p 34 • - important for forming some amino acids and enzymes; • in organic (dead plants and animals) and inorganic (sulfur • containing rocks) deposits • released into the environment by decomposition of organic • matter, erosion, volcanoes, salt spray from oceans • occurs as H2S then SO2 in air and water, and SO4 in water • and soil; forms H2SO4 in water and falls with rain to earth • and becomes available (too much causes acid rain) • decomposers (bacteria and fungi) release sulfur from • organic material • plants mainly get S from SO4 in soil and water; animals by • eating plants and other animals

9. mining (especially coal) and industry release S and acidifies • the environment from runoff from strip mines and burning • poor grades of coal • H20 p 35 • hydrologic cycle - water comes from oceans to continents • via rainfall; it then evaporates, gets stored (surface or • ground), or goes back via rivers • not much in atmosphere and the turnover rate is high • human activities can affect cycle: reduce aquifers or change • evaporation rates and runoff by construction of cities

12. Energy Flow - from sun to plants (photosynthesis) to system • (consumers in the food web) then lost as heat • - laws of thermodynamics • 1) energy cannot be created or destroyed • 2) when energy is transferred, it is transformed, and much is • lost to unusable forms (heat) • plants capture energy in chemical bonds which animals in • the food web eat and pass on; energy does not cycle but • flows out of the system as heat • - photosynthesis • — uses CO2 and H2O in a reaction by light energy; • green chlorophyll captures light energy • — sugars and O2 are produced; also other organic products • (fats, vitamins, and proteins) • — 6 CO2 + 6 H2O w/sunlight yields C6H12O6 + 6 O2

13. - decomposition - break down of organic compounds, releases CO2 and H2O, returns nutrients to inorganic state (vitamins and minerals are freed from C based molecules) — done by microflora (fungi for plant litter, bacteria for animal matter; actually do the decomposition) and detritivores (invertebrates that feed on detritus, dead organic matter, and really just break it down into smaller bits) — other important factors: activities and ingestion by larger organisms and leaching by precipitation — detritivores (mites, protozoans, nematodes, earthworms, millipedes) fragment organic material and inoculate it with bacteria and fungi — microbivores (larval beetles, flies, mites, amoebas) feed on nutrients and energy of microflora

14. — decomposers temporarily remove nutrients from • circulation (nutrient immobilization) • Food Webs and Energy Pyramids • autotrophs - producers; produce own food; living base of • food web • heterotrophs - consumers; use producers or other • consumers as food • trophic levels - feeding levels through which energy is • passed; begins with producers • food chain - path of energy flow from producer to consumer; • better seen as food web • order: • primary producers (phytoplankton and large plants)

15. 2) primary consumers - herbivores or prey; land and water • grazers (carp, ducks, deer, mice) and zooplankton • 3) secondary consumer (carnivores or predators); can go to • more levels • – omnivores - eat both autotrophs (plants) and heterotrophs • – other contributors: decomposers, detritivores, • microbivores, scavengers, saprophytes (fungi that feed on • dead plant material; decomposers), and parasites • – intricate “web” of energy exchange; many organisms shift • roles and can be predators and prey • about 90% loss of energy at each step of the web (energy is • lost as heat when chemical bonds are broken and used to • warm bodies); 2nd law of thermodynamics

16. Relative Number Of Organisms As You Follow A Food Web Relative Biomass Of Organisms As You Follow A Food Web

18. – limits how much energy, how many individuals, and how much biomass can accumulate up chains; called ecological pyramids – fisheries managers deal with 2nd and 3rd level consumers; wildlife managers mostly deal with 1st level consumers (predators at higher levels cannot reach numbers of 1st level consumers)