4c - Cycles within Ecosystems

Assimilation

（营养）同化作用 ((yíngyǎng) tónghuà zuòyòng) The process by which living organisms incorporate absorbed nutrients (e.g., carbon from glucose, nitrogen from nitrates) into their own cells and tissues to build complex organic molecules.

Carbon Cycle

碳循环 (tàn xúnhuán) The continuous movement of carbon atoms between the atmosphere, oceans, land, and living organisms, through processes like photosynthesis, respiration, decomposition, combustion, and fossilisation.

Combustion

燃烧 (ránshāo) The process of burning substances, especially fossil fuels or organic matter, which rapidly releases carbon dioxide (and other gases) into the atmosphere.

Decomposition

分解作用 (fēnjiě zuòyòng) The breakdown of dead organic matter (dead plants, animals, and waste) by decomposers (mainly bacteria and fungi), releasing nutrients (like carbon and nitrogen compounds) back into the ecosystem.

Denitrifying bacteria

反硝化细菌 (fǎnxiāohuà xìjūn) Bacteria, typically found in anaerobic soil conditions, that convert nitrates (NO₃⁻) back into nitrogen gas (N₂), which is then released into the atmosphere. Part of the nitrogen cycle.

Feeding

摄食 (与同化) (shèshí (yǔ tónghuà)) The process by which organisms consume other organisms, transferring organic compounds (containing carbon and nitrogen) along food chains, followed by assimilation of these compounds.

Fossilisation

化石化作用 (huàshíhuà zuòyòng) The process by which the remains or impressions of dead organisms are preserved as fossils over geological time. Incomplete decay under specific conditions can lead to the formation of fossil fuels.

Legumes

豆科植物 (dòukē zhíwù) Plants (e.g., peas, beans, clover) that often have a symbiotic relationship with nitrogen-fixing bacteria in their root nodules, playing a key role in the nitrogen cycle.

Mutualism

互利共生 (hùlì gòngshēng) A type of symbiotic relationship between two different species where both organisms benefit from the interaction (e.g., nitrogen-fixing bacteria and legume plants).

Nitrifying bacteria

硝化细菌 (xiāohuà xìjūn) Bacteria in the soil that carry out nitrification in two steps: first, converting ammonia (NH₃) or ammonium ions (NH₄⁺) to nitrites (NO₂⁻), and then converting nitrites to nitrates (NO₃⁻). Part of the nitrogen cycle.

Nitrogen-fixing bacteria

固氮细菌 (gùdàn xìjūn) Bacteria that convert atmospheric nitrogen gas (N₂), which is unusable by most organisms, into ammonia (NH₃) or ammonium ions (NH₄⁺), making nitrogen available to plants. Can be free-living or in root nodules.

Nitrogen Cycle

氮循环 (dàn xúnhuán) The continuous movement of nitrogen atoms between the atmosphere, soil, water, and living organisms, involving processes like nitrogen fixation, nitrification, denitrification, decomposition, and assimilation.

Photosynthesis

光合作用 (guānghé zuòyòng) The process by which producers (mainly plants and algae) use light energy to convert carbon dioxide and water into glucose (an organic carbon compound) and oxygen. Removes CO₂ from the atmosphere.

Respiration

（细胞）呼吸作用 ((xìbāo) hūxī zuòyòng) The process by which all living organisms (plants, animals, microorganisms) break down organic compounds (like glucose) to release energy, producing carbon dioxide and water as by-products. Returns CO₂ to the atmosphere.

Root nodules

根瘤 (gēnliú) Swellings on the roots of leguminous plants that house symbiotic nitrogen-fixing bacteria (e.g., Rhizobium).

Water Cycle (Hydrological Cycle)

水循环 (shuǐ xúnhuán) The continuous movement of water on, above, and below the surface of the Earth, involving processes like evaporation, transpiration, condensation, precipitation, and runoff.

Denitrification

反硝化作用 (fǎnxiāohuà zuòyòng) The process, carried out by denitrifying bacteria (usually in anaerobic conditions), where nitrates (NO₃⁻) in the soil are converted back into nitrogen gas (N₂), which returns to the atmosphere.

Nitrification

硝化作用 (xiāohuà zuòyòng) A two-step process carried out by nitrifying bacteria in the soil: 1. Oxidation of ammonia (NH₃) or ammonium ions (NH₄⁺) to nitrites (NO₂⁻). 2. Oxidation of nitrites (NO₂⁻) to nitrates (NO₃⁻).

Nitrogen Fixation

固氮作用 (gùdàn zuòyòng) The process of converting atmospheric nitrogen gas (N₂), which is largely unusable by most organisms, into ammonia (NH₃) or ammonium ions (NH₄⁺). This can be done by nitrogen-fixing bacteria (in soil or root nodules) or by lightning.