1. BIO-GEO-CHEMICAL CYCLES
Nutrient cycling in an ecosystem

2. Biogeochemical Cycles (Matter moving through the environment)
All living organisms need certain elements/compounds for life processes
Ex: your cells need C,H,O,P,N & S in order to live and reproduce (make more cell)
Cycles in nature keep these elements “moving” from organisms to organism (and sometimes into the atmosphere)

3. Biogeochemical Cycles (Matter moving through the environment)
The flow of a nutrient from the environment to living organisms and back to the environment
Main reservoir for the nutrient is in the environment or the abiotic reservoir.
Transfer rates to and from abiotic reservoirs are usually lower than the rates of exchange between and among organisms or biotic reservoirs.
Matter is recycled through an ecosystem – not one a way flow as with energy.

4. Three Main Abiotic Reservoirs
Hydrologic cycle
Water, (hydrogen
and oxygen)
Atmospheric cycles
Nitrogen, carbon, oxygen
Sedimentary cycles
Phosphorus and sulfur

6. WATER CYCLE
Water Cycle - Earth’s water supply is constantly recycled throughout the biosphere:
Evaporation – water vapor leaves the oceans and joins the atmosphere.
Transpiration – water vapor evaporates off of plant leaves.
Condensation – water vapor in the atmosphere forms clouds.
Precipitation – water vapor in the atmosphere falls to the ground (rain.)

7. Carbon Cycle
Carbon moves through the atmosphere and food webs on its way to and from the ocean, sediments, and rocks.
Atmospheric carbon is mainly carbon dioxide
Carbon dioxide is added to atmosphere
Aerobic respiration, volcanic action, burning fossil fuels, decomposition of organic materials
Removed by photosynthesis

8. Carbon Cycle Diagram Carbon in Atmosphere
Plants use carbon to make food
Animals eat plants and take in carbon
Plants and animals die
Decomposers break down dead things, releasing carbon to atmosphere and
soil
Bodies not decomposed — after many years, become part of oil or coal deposits
Fossil fuels are burned; carbon is returned to atmosphere
Carbon slowly released from these substances returns to atmosphere

9. Carbon Cycle Diffusion Atmosphere Bicarbonate, carbonate Terrestrial
photosynthesis
TERRESTRIAL ROCKS
volcanic action
weathering
Diffusion
Atmosphere
Bicarbonate, carbonate
Terrestrial
Rocks
Land Food Webs
Marine food
webs
Soil Water
Peat, Fossil Fuels
Marine Sediments

10. Human Impact Fossil fuels release carbon stores very slowly
Burning anything releases more carbon into atmosphere — especially fossil fuels
Increased carbon dioxide in atmosphere increases global warming
Fewer plants mean less CO2 removed from atmosphere

11. The Carbon Cycle
Plants

12. Nitrogen Cycle

13. What is Nitrogen?
Nitrogen is the most abundant element in the Earth’s atmosphere.
Nitrogen cannot be absorbed directly by plants and animals until it is converted into compounds they can use. This process is called the Nitrogen Cycle.

14. Nitrogen Cycle Steps
Step 1- Nitrogen Fixation- Special bacteria convert nitrogen gas (N2) to ammonia (NH3) which the plants can use.
Step 2- Nitrification- Nitrification is the process which converts the ammonia into ions which the plants can take in as nutrients.

15. Nitrogen Cycle Steps
Step 3- Ammonification- After all of the living organisms have used the nitrogen, decomposer bacteria convert the nitrogen-rich waste compounds into simpler ones.
Step 4- Denitrification- This is the final step in which other bacteria convert the simple nitrogen compounds back into nitrogen gas (N2), which is then released back into the atmosphere to begin the cycle again.

16. decomposition by bacteria & fungi
Nitrogen in
the air
nitrogen fixing plant
eg pea, clover
animal protein
plant made
protein
dead plants & animals
urine & faeces
denitrifying
bacteria
root nodules
(containing nitrogen
fixing bacteria)
decomposition by bacteria & fungi
nitrates absorbed
nitrates
ammonia
bacteria
nitrites
bacteria
(nitrifying bacteria)

17. How do humans affects the Nitrogen Cycle?
Nitric Oxide (NO) is released into the atmosphere when any type of fuel is burned. This includes byproducts of internal combustion engines.
Nitrous Oxide (N2O) is released into the atmosphere through bacteria in livestock waste and commercial fertilizers applied to the soil.

18. How do humans affects the Nitrogen Cycle? (cont.)
Removing nitrogen from the Earth’s crust and soil when we mine nitrogen-rich mineral deposits.
Discharge of municipal sewage adds nitrogen compounds to aquatic ecosystems which disrupts the ecosystem and kills fish.

19. Phosphorus Cycle
Phosphorus is part of phospholipids, nucleic acids, and energy metabolism
It is the most prevalent limiting factor in ecosystems because it is slower moving than other cycles.
Main reservoir is Earth’s crust; no gaseous phase (it never enters the atmosphere – like carbon and nitrogen)
Plants absorb phosphate from soil and phosphatizing bacteria return it back to it’s abiotic reservoir when they decompose organic wastes.
Phosphates returns (moved) via weathering, volcanic activity, ect.

21. Homeostasis Exists in Nutrient Cycles
In a stable ecosystem, biogeochemical cycles show homeostasis.
Meaning input = output
According to the Gaia theory by Lovelock, the Earth (biosphere) is a self-regulating system. The evolution of life and the planet are intimately connected as if the earth is a big “organism” itself.
Human impact from clear-cutting, slash/burn, and greenhouse gases can seriously affect the homeostasis of the cycles!