This definitions covers Key Definitions within Carbon Cycle for GCSE Biology. Topic 3: Carbon Cycle It is section 7 of 12 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 7 of 12
Practice
15 questions
Recall
20 flashcards
Key Definitions
Carbon cycle: The continuous movement of carbon atoms through the atmosphere, living organisms, soil, oceans, and geological materials via processes including photosynthesis, respiration, decomposition, and combustion.
Photosynthesis: The process by which producers use light energy to convert CO2 and water into glucose and oxygen — the main route by which carbon enters living systems from the atmosphere.
Respiration: The metabolic process in which organic molecules are broken down to release energy — CO2 is released as a waste product, returning carbon to the atmosphere from living organisms.
Combustion: The burning of organic materials (wood, fossil fuels, biomass) which oxidises carbon compounds to release CO2 into the atmosphere.
Decomposition: The breakdown of dead organic material by decomposers (bacteria and fungi), releasing CO2 through the decomposers' own respiration and returning mineral ions to the soil.
Fossil fuels: Carbon-rich materials (coal, oil, natural gas) formed from incompletely decomposed organic matter over millions of years under heat and pressure; a major long-term carbon store.
Carbon sink: A reservoir that absorbs more carbon than it releases (e.g., forests, oceans, peat bogs). Carbon sources release more carbon than they absorb (e.g., burning fossil fuels).
Greenhouse effect: The process by which greenhouse gases (including CO2 and methane) in the atmosphere absorb outgoing infrared radiation from Earth's surface and re-emit it, warming the planet.