Carbon, Nitrogen, Phosphorus, and Water Cycles

Objectives/EKs/Skills
- Movement of carbon-containing molecules (CO2, glucose, CH4) between sources and sinks.
Carbon Cycle Steps
- Fast Processes: e.g., fossil fuel (FF) combustion.
- Slow Processes: e.g., sedimentation and burial.
Atmospheric Carbon
- Atmosphere serves as a key carbon reservoir.
- Increasing CO2 levels lead to global warming.
Photosynthesis & Cellular Respiration
- Performed by plants, algae, and phytoplankton.
- Photosynthesis: Removes CO2 from atmosphere and converts it to glucose.
- Cellular Respiration: Releases CO2 back into the atmosphere.
- Both processes are rapid, maintaining a balance in the carbon cycle.
Burial, Extraction, & Combustion
- Burial: Slow geological storage of carbon in underground sinks (sed. rock, fossil fuels).
- Formation of Fossil Fuels:
- From organic matter (e.g., dead ferns for coal, marine algae for oil).
- Net Increase in CO2: Extraction and combustion processes lead to higher atmospheric CO2 levels compared to burial.

Objectives/EKs/Skills
- N is a critical nutrient for plants and animals.
- Atmospheric N is mainly a reservoir, with N predominantly in the form of N2 gas.
Importance of Nitrogen
- Essential for DNA and amino acids, thus for protein synthesis.
- N reservoirs (plants, soil, atmosphere) hold nitrogen for shorter periods than carbon reservoirs.
Nitrogen Fixation
- Synthetic Fixation: Humans convert N2 gas into nitrate (NO3\^-) via fossil fuel combustion.
- Bacterial Fixation: Bacteria convert N2 into ammonia (NH3), usable by plants.
- Rhizobacteria assist legumes by fixing N in exchange for amino acids.
Key Steps of the Nitrogen Cycle
- Nitrification: Conversion of NH4\^+ to nitrite (NO2\^-) and nitrate (NO3\^-).
- Ammonification: Decomposition converts organic matter back to NH3.
- Assimilation: Uptake of N by plants (NO3 or NH3) and incorporation into the body of animals.
- Denitrification: Conversion of soil nitrate (NO3) back to nitrous oxide (N2O) gas.
Human Impacts on Nitrogen Cycle
- Leaching & Eutrophication: Excess nitrates from fertilizers can lead to water pollution.
- Climate Impacts: N2O as a greenhouse gas influences climate change; NH3 can cause acid precipitation.

Objectives/EKs/Skills
- Slow-moving compared to other cycles; contains major reservoirs (rocks/sediments).
- No gaseous form; phosphorus does not enter the atmosphere.
Phosphorus Importance
- Needed for DNA, ATP (energy), and bone structure in some animals.
- Often a limiting nutrient in ecosystems due to slow cycling.
Phosphorus Sources
- Natural: Weathering of rocks releases phosphate (PO4\^{3-}).
- Synthetic: Mining phosphate minerals; fertilizers and detergents introduce phosphates into ecosystems.
Assimilation
- Plants absorb phosphates and incorporate into tissues; animals gain P by consuming plants or other animals.
- Decomposition and waste return phosphate to soil.
Sedimentation & Geological Uplift
- Sediments can turn into sedimentary rock over time, starting the cycle anew.
Eutrophication
- Excess nutrients (N and P) lead to algae blooms that block sunlight and deplete O2, harming aquatic life.
- Can result from fertilizer runoff or waste contamination, creating a negative feedback loop in ecosystems.

Objectives/EKs/Skills
- Movement of water (H2O) among various states and reservoirs.
Energy in the Water Cycle
- Driven by solar energy, enabling evaporation and transpiration.
Sources of Water
- Evapotranspiration: Combined process of water movement from soil to atmosphere.
- Transpiration: Water absorbed by plant roots released through stomata.
Runoff & Infiltration
- Precipitation either contributes to surface water (runoff) or infiltrates soil (infiltration).
- Water reservoirs: groundwater (aquifers) and surface waters (lakes/rivers).
- Ensure water is usable for humans and ecosystems, with concerns about pollutant runoff affecting water quality.