IB Environmental systems and societies 2.3 Biogeochemical Cycles Key Definitions

Ammonification (a type of decomposition) converts organic nitrogen (e.g., amino acids, urea) into ammonia or ammonium ions.

Biogeochemical cycles are the natural pathways through which essential elements like carbon, nitrogen, and phosphorus circulate between the biotic (living) and abiotic (non-living) components of Earth.

Carbon sequestration is the process of capturing atmospheric carbon dioxide (CO₂) and storing it in solid or liquid form.

Cellular respiration is the conversion of stored chemical energy in glucose into a usable chemical form that fuels metabolic processes in living cells.

Decomposition is the breakdown of organic nitrogen in dead organisms and waste products into ammonium (NH₄⁺).

Denitrification is the conversion of nitrates (NO₃⁻) back into nitrogen gas (N₂), which is released into the atmosphere.

The enhanced greenhouse effect refers to additional warming caused by increased concentrations of greenhouse gases from human activities.

Eutrophication is a process where excess nutrients, primarily nitrates and phosphates, enter aquatic ecosystems, triggering a cascade of ecological changes.

Limestone is a sedimentary rock composed primarily of CaCO₃, formed through both biological and chemical precipitation processes.

Methanogenesis is the biological process by which methanogenic archaea (bacteria-like microorganisms) produce methane (CH₄) from organic material in anaerobic environments.

An artificial system growing a single species of crop with minimal biodiversity, resulting in low resilience.

A mutualistic nitrogen-fixing relationship is a symbiotic interaction between plants and nitrogen-fixing bacteria, where both organisms benefit.

Nitrification is the conversion of ammonia (NH₃) to nitrates (NO₃⁻).

The nitrogen cycle is a biogeochemical cycle through which nitrogen is transferred and transformed between the atmosphere, biosphere, hydrosphere, and lithosphere, ensuring its continued availability to living organisms.

Nitrogen fixation is the conversion of nitrogen gas (N₂) from the atmosphere into ammonia (NH₃).

Ocean acidification is the process by which the ocean becomes more acidic due to increased levels of dissolved carbon dioxide.

Peat is a dense, carbon-rich accumulation of partially decomposed plant material found in waterlogged ecosystems.

Phytoplankton are microscopic organisms capable of photosynthesis

A planetary boundary is a scientifically defined threshold beyond which human activities risk causing abrupt or irreversible environmental change.

The average time a molecule remains in the atmosphere before being removed through physical or chemical processes.

Residence time is the average duration that a carbon atom remains in a particular store before moving to another part of the carbon cycle.

A sink is a location in an ecosystem where a chemical element is accumulated or stored over time, leading to a net increase in that element in that location.

A source is a location or process in which a chemical element is released into the environment, leading to a net increase in the amount of the element in the atmosphere or other parts of the ecosystem.

Stores are components in the ecosystem where elements are held for relatively long periods.