APES: Nitrogen Cycle & Carbon Cycle (Video Notes)

Vocabulary flashcards covering key terms from the Nitrogen Cycle and the Carbon Cycle based on the provided video notes.

Nitrogen fixation

Process of converting N2 gas into biologically usable forms (NH3 or NO3-), carried out by soil bacteria and root-nodule bacteria; industrial (synthetic) fixation also produces usable nitrate.

Rhizobacteria

Bacteria that live in root nodules of legumes and fix atmospheric N2 into ammonia (NH3) for the plant in exchange for carbohydrates.

Legumes

Plants such as peas and beans that host nitrogen-fixing bacteria in root nodules.

Ammonia (NH3)

Form of nitrogen produced by fixation; readily used by plants and microbes; in soil it often becomes ammonium (NH4+).

Ammonium (NH4+)

A positively charged form of nitrogen in soil, produced from ammonification and nitrification processes.

Nitrification

Microbial oxidation of NH4+ to NO2- and then to NO3- (nitrate); performed by nitrifying bacteria.

Nitrate (NO3-)

A nitrogen form usable by plants, produced by nitrification and taken up through plant roots.

Assimilation

Uptake of nitrates (NO3-) or ammonium (NH4+) by plants and incorporation into organic molecules.

Ammonification

Decomposition of nitrogen-containing waste or dead biomass to form NH4+ (ammonium) by soil bacteria and decomposers.

Denitrification

Conversion of nitrates (NO3-) to nitrogen gas (N2) by denitrifying bacteria, returning N to the atmosphere.

Nitrogen reservoir

A storage pool for nitrogen (e.g., atmosphere, soil, biomass) where N is held for varying times.

Atmosphere (N2)

Main nitrogen reservoir; N2 gas makes up about 78% of Earth's atmosphere and is largely inert until fixed.

N2O (nitrous oxide)

A potent greenhouse gas produced during nitrification/denitrification; released from soils and manure management.

Ammonia volatilization

Process where NH4+ in soil is converted to NH3 gas and released into the atmosphere, especially with excess fertilizer.

Leaching

Movement of dissolved nitrates (NO3-) through soil with water, potentially reaching groundwater.

Runoff

Nitrates and other pollutants being carried into surface waters by rainfall or irrigation, causing eutrophication.

Synthetic fixation (Haber-Bosch)

Industrial process that fixes atmospheric N2 into ammonia, enabling production of nitrogen fertilizers.

Nitrate (NO3-) uptake

Plants absorb NO3- through roots to synthesize amino acids and proteins.

Nitrogen cycle impact (N2O, fertilizer use)

Human activities can increase N2O emissions and cause ammonia volatilization and nitrate pollution.

Nitrification vs. Denitrification

Nitrification converts NH4+ to NO2- and NO3-; denitrification converts NO3- to N2, closing the cycle.

Nutrient cycle balance

The natural nitrogen cycle moves nitrogen between reservoirs with no long-term net change in the ecosystem absent human inputs.

Carbon cycle

Movement of carbon-containing molecules (CO2, glucose, CH4) between sources and sinks in ecosystems.

Carbon source

Processes that add CO2 to the atmosphere (e.g., fossil fuel combustion, respiration, deforestation).

Carbon sink

Processes or reservoirs that absorb more carbon than they release (e.g., oceans, forests, soils).

Photosynthesis

Plants and algae convert CO2 from the atmosphere into sugars using sunlight and water.

Cellular respiration

Organisms break down sugars to release energy, emitting CO2 back to the atmosphere.

Decomposition

Breakdown of dead organisms and waste by fungi and bacteria, releasing carbon compounds.

Sedimentation

Accumulation of carbon in sediments (organic matter or carbonates) over time.

Burial

Geological process storing carbon in underground sinks like sedimentary rocks or fossil fuels.

Fossil fuels

Coal, oil, and natural gas formed from ancient organic matter; burning them releases CO2.

Combustion

Burning of fossil fuels that releases CO2 into the atmosphere.

Extraction

Mining or harvesting fossil fuels, enabling energy use and subsequent CO2 release upon combustion.

Ocean–atmosphere CO2 exchange

Direct, rapid transfer of CO2 between the surface of the ocean and the atmosphere, helping balance levels.

Ocean acidification

Decreased ocean pH due to dissolved CO2 forming carbonic acid, affecting calcium carbonate shells and organisms.

Carbon reservoir

A storage pool that contains large amounts of carbon, such as the atmosphere, oceans, or soils; a carbon sink stores more carbon than it releases.

Dissolution of CO2 in seawater

CO2 dissolves in seawater, forming carbonic acid and bicarbonate, influencing ocean chemistry.

Sedimentation of carbonates

Calcium carbonate from shells and skeletons sinks to the ocean floor, becoming sedimentary rock.

Fossilization

Long-term preservation of organic matter leading to fossil fuels or sedimentary rocks.

Ocean acidification effects

Lowered ocean pH can harm calcifying organisms (corals, shellfish) and disrupt marine ecosystems.