Biogeochemical Cycles Three major biogeochemical cycles are shown

Biogeochemical Cycles • Three major biogeochemical cycles are shown in this presentation: – The water cycle. Are plants and animals really necessary for this one? – The carbon cycle. Don’t confuse this one with the obvious interaction between photosynthesis and respiration! Note that O 2 is not shown. – The nitrogen cycle. Bacteria, bacteria.

Biogeochemical Cycles - Water Cycle • Water can stay as H 2 O in the bodies of water (oceans, rivers, aquifers, icebergs…) • Water can cycle physically, through precipitation and evaporation • Water can be incorporated into the food chain, and recycled back through respiration (both animals and plants)

The Water Cycle Rain Clouds precipitation respiration evaporation (from bodies of water) transpiration evaporation (from soil) drinking excretion absorption Adapted from Bioreview Sheet 1604, Carolina Biological Supply Co. , Burlington NC, © 1966 Ground Water Bodies of Water physical animals plants

Biogeochemical Cycles - Carbon Cycle • Think about “source and sink” • Carbon is stored short-term in the components of living organisms • Carbon can be stored long-term in fossil fuels, and also in relatively insoluble compounds (bone, sea shells) • Even though oxygen is produced in photosynthesis, note that it is not, strictly speaking, a part of the carbon cycle.

The Carbon Cycle Atmospheric CO 2 photosynthesis respiration Respiration respiration (burning) Fermentation & respiration nutrition Decomposers Adapted from Bioreview Sheet 1600, Carolina Biological Supply Co. , Burlington NC, © 1966 Organic waste Fossil fuel

Biogeochemical Cycles - Nitrogen Cycle • Think about “source and sink” • Nitrogen is unusable to most organisms in its elemental form, N 2 • It’s most important changes occur through the action of various bacteria • Nitrogen can be found in inorganic compounds and organic compounds (proteins) • See the next slide for a discussion of the bacteria

Nitrogen Cycle Bacteria • Nitrogen-fixers. Take elemental N 2 and convert it to nitrates that are usable by plants. • Decomposers. Break down organic materials and release ammonium (NH 4), a poison. • Nitrite bacteria. Convert ammonium compounds to nitrites • Nitrate bacteria. Convert nitrites to nitrates, an inorganic usable by plants. • Denitrifiers. Convert nitrates, nitrites, and ammonium compounds to elemental N 2.

The Nitrogen Cycle Atmospheric N 2 NH 2 COOH plant & animal amino acids, proteins Nitrogen fixing bacteria Denitrifying bacteria NO 3 nitrate Adapted from Bioreview Sheet 1602, Carolina Biological Supply Co. , Burlington NC, © 1966 Decaying material Nitrate bacteria Decomposers Nitrite NO 2 NH 4 bacteria nitrite ammonium

The Oxygen Cycle Atmospheric O 2 and dissolved O 2 Cellular Respiration Photosynthesis H 2 O CO 2

Productivity • Gross productivity - total amount of energy photosynthesized by the autotrophs • Net productivity - total amount of energy available to the heterotrophs • A good measure of the health of an ecosystem is its primary productivity

Primary Productivity • A way you can do this is to measure the amount of activity performed by the autotrophs of the system – Remember that some captured photosynthetic energy is stored in plant tissue, and that plants themselves are eaten by the heterotrophs… • So, the total amount of photosynthesis is a measure of the first (primary) energy stored in an ecosystem

Biomagnification • Concentration and transportation of chemicals through food webs. • DDT: – Chemical pesticide used in 1950 s &1960 s – Reduced population of mosquitoes and the accompanying diseases. – Rachael Carson identified destruction DDT had on ecosystems.

Carson / DDT • http: //www. youtube. com/watch? v=9 x. A 7 XNezc 0 • http: //www. youtube. com/watch? v=ky. Yp w. OTta. LI • http: //www. youtube. com/watch? v=QNN l_u. Wm. QXE