1	ECOSYSTEM Material Cycles Ultimately material (elements) must cycle among the compartments in which it is found. The global paths that an element takes is referred to as its biogeochemical cycle.
2	Reading Chapter 54 Today we concentrate on the movement of materials p.1252-1262. Figure 54.17 and 54.19 describe two major biogeochemical cycles.
3	Ecosystem We used the word ecosystem to include not only the living organisms of a community, but also the abiotic components that are important to functioning of organisms. Abiotic components include: Atmosphere and its molecules. Water and molecules dissolved in it. Any other non-living part important to function.
4	Ecosystem Ecology Ecology that focuses on the flow of energy and materials is called ecosystem ecology. Typically, ecosystem ecologists are not interested in species, but rather aggregated groups such as plants or carnivores.
5	Material Cycles (but energy flows) Energy flows from a source (and eventually is dissipated). Elements (material) are not gained or lost, the constant total amount does move among compartments holding different forms. Altogether the movement of an element among the various compartments in which it is found is called a cycle.
6	Biomass ‘Pyramids’ If the producers grow rapidly, it may be possible for there to be more biomass of consumers than of producers. Oligotrophic aquatic systems frequently have a greater mass of zooplankton than of phytoplankton. Terrestrial systems almost always have mass pyramids close to energy pyramid (which always has less at subsequent levels).
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8	Ingestion and Excretion Not all the food that is eaten is absorbed –some is excreted. Not all the compounds that are absorbed are metabolized (broken down) equally efficiently. Compounds/elements that are absorbed, but not metabolized accumulate in the body. The amount an individual has is called the ‘body burden’.
9	Heavy Metals Neither lead (Pb) or mercury (Hg) have any positive contribution to the body. Lead and mercury have a variety of negative effects on organisms. Lead and mercury are excreted very slowly and accumulate in the body. Lead and mercury continue to be major health concerns for humans.
10	BIOMAGNIFICATION Toxicity of compounds increases with increasing concentration. Concentration increases at each trophic level.
11	Biogeochemical Cycling Bio – stands for the biosphere, the living organisms, Geo – stands for the geological compartments, the earths crust, ocean and atmosphere, Chemistry is involved because the elements frequently are transformed among a variety of compounds, e.g. NH₃, N₂, NO₂^- & NO₃^-
12	Material Cycles Compartments are also called reservoirs. Movement into a compartment is input. Movement out of a compartment called output. Amount in the compartment called pool size. If the rates of output is low the pool size is likely to be large.
13	Turnover or Residence Time, the length of time in the pool Compounds that can be made by biological systems can be broken down by biological systems (otherwise those compounds would build up indefinitely). Simple sugars are rapidly metabolized and turnover quickly. Lignin,a part of wood, is broken down slowly and therefore lasts for a long time.
14	Biosphere Recycling Dead animals and plants are called detritus. Dead animals and plants are recycled by organisms called decomposers. Some parts are recycled quickly, others take a lot longer to break down. Microorganisms are a necessary part of recycling.
15	Detritus Detritus is dead organic mater. The leaves that fall from deciduous trees are the classic example of detritus. Detrivores eat detritus, e.g. shred and chew it. In Illinois, oak leaves take about 3 years to completely disappear – leaves of other trees take less time.
16	Decomposers Most of the difficult to digest compounds are broken down by fungi or bacteria. Decomposition is faster with high levels of moisture at higher temperatures because fungi and bacteria need high moisture. Decomposition is therefore usually more rapid in the tropics than at higher latitudes.
17	Animals that use wood have symbionts Termites eat wood and extract energy from it. The termite gut has flagellates (Protista) that harbor bacteria. The termites chews the wood into pieces so small that the flagellates can engulf them and then the bacteria make the enzymes that digest the wood. Ruminants, e.g. Cows, also are dependent on protista and prokaryotes in their rumen for much digestion.
18	Local cycling of material Rain tends to leach nutrients from the soil into the ground water. Plant roots capture these nutrients and transport them to the leaves. When the leaves die and fall to the ground the nutrients again enter the soil. See the following figure (54.13)
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20	Losses and Gains of Nutrients Local systems can lose or gain substantial amounts of various nutrients. Changes in the local amount of nutrient can dramatically impact the local system, i.e. eutrophication of lakes. At the global scale we used to think local losses and gains balanced out, but humans have increased the amount of many elements in the biosphere.
21	Global Carbon Cycle Carbon dioxide in atmosphere. 370 ppm = parts per million. Carbon dioxide dissolved in ocean is 50 times the amount in atmosphere. Living organisms generate flux thru respiration. Geological forms of carbon: Oil Graphite Coal Diamond
22	Global Carbon Cycle
23	Global Nitrogen Cycle While the concentration of carbon dioxide has increased considerably since 1800, the percent increase is much less than N. The amount of nitrogen added to the biosphere by humans is almost equal that of natural sources. N₂ is the most common gas of our atmosphere, but it is very unreactive.
24	Amounts of Nitrogen moving into biosphere each year
25	VOCABULARY Abiotic Ecosystem Residence time Decomposer Detritus Lignin Biomagnification Biogeochemical cycling Global carbon cycle Nitrogen fixation Nitrogen fertilizer Heavy metal