Nutrient Cycles - Carbon, Nitrogen, Phosphorus, and Hydrologic (Water) Cycle

Vocabulary flashcards covering major concepts from the Carbon, Nitrogen, Phosphorus, and Hydrologic cycles, including sinks/sources, processes, and human impacts.

Carbon Cycle

Movement of carbon in all forms (CO2, glucose C6H12O6, CH4) among sinks and sources; rates vary and imbalances drive inputs/outputs.

Sinks

Reservoirs that store carbon (oceans, plants, soil) and can absorb more than they release.

Sources

Reservoirs that release more carbon than they store (e.g., fossil fuel combustion, animal agriculture producing CH4, deforestation releasing CO2).

Direct Exchange

CO2 moves directly between atmosphere and ocean; positive feedback can lead to ocean acidification.

Photosynthesis

Process by which plants convert CO2 into glucose, removing CO2 from the atmosphere.

CaCO3 formation

Organisms like corals and mollusks form calcium carbonate (CaCO3) using CO2 for their shells/exoskeletons.

Sedimentation (Carbon)

CaCO3 precipitates and settles to the ocean floor, creating a long-term carbon reservoir.

Burial

Slow geological process that forms rock and fossil fuels, sequestering carbon over long times.

Fossil Fuels

Humans burning oil, natural gas, and coal releases CO2 via combustion.

Weathering

Weathering of carbonate rocks (calcite) breaks down into CO2 and carbonic acid (H2CO3).

Volcanic Eruptions

Volcanoes release CO2 from the Earth's interior into the atmosphere.

N2 nitrogen cycle

Movement of nitrogen between atmosphere and soil; N2 makes up about 78% of the atmosphere and is largely unusable by most organisms.

N2 unusable

N2 is a major atmospheric component but is not directly usable by most plants/animals.

Nitrogen Fixation

Conversion of N2 to ammonia or nitrate; occurs via lightning or biological fixation by Rhizobacteria in legumes.

Ammonification

Decomposers convert waste and dead biomass to NH3 (ammonia).

Nitrification

Bacteria convert NH3 to NO2- and then NO3-, the usable form of nitrogen for organisms.

Denitrification

Nitrate (NO3-) is reduced to elemental N2 by facultative anaerobes when O2 is limited.

Assimilation (Nitrogen)

Nitrates are used by plants to synthesize amino acids, proteins, and nucleic acids; animals obtain nitrogen by consuming plants/other organisms.

Eutrophication

Excess nitrogen and phosphorus lead to algae blooms; sunlight is blocked, oxygen is depleted as decomposers break down blooms.

Phosphorus Cycle

Movement of phosphorus between rocks, soils, and organisms; no atmospheric gas phase; cycles slowly.

Weathering of phosphate rocks

Weathering releases phosphate (PO4^3-) into water/soil; phosphate is often a limiting nutrient due to slow weathering.

PO4^3- (Phosphate)

Phosphate ion, essential nutrient for DNA, ATP, and bones; typically dissolved in water as PO4^3-.

Synthetic fertilizers

Human-made phosphate fertilizers added to soils; runoff carries phosphorus into waterways.

Sedimentation (Phosphorus)

Phosphate sediments settle and can form sedimentary rock over long times.

Geological uplift

Tectonic uplift exposes phosphate rocks to weathering, re-starting the P cycle.

Assimilation & Decomposition (P)

Plants assimilate phosphate; decomposition returns phosphate to soil.

Hydrologic (Water) Cycle

Movement of water through reservoirs (oceans, atmosphere, land) driven by solar energy.

Evaporation

Liquid water becomes water vapor in the atmosphere due to heating.

Transpiration

Plants release water vapor from leaves as part of water transport from roots.

Evapotranspiration

Total water entering the atmosphere from both evaporation and plant transpiration.

Precipitation

Water returns from atmosphere to land as rain/snow, recharging surfaces or infiltrating soil.

Runoff

Precipitation that flows over land into rivers/lakes, carrying pollutants.

Infiltration

Water infiltrates soil to recharge groundwater aquifers.

Groundwater

Freshwater stored in aquifers; a key reservoir recharged by infiltration.