Nutrient Cycles: Carbon

This lesson covers the carbon cycle, including the processes of photosynthesis, respiration, decomposition, combustion, and fossilisation, as well as carbon sinks and sources, as required by the Edexcel A-Level Biology specification (9BI0), Topic 10 -- Ecosystems.

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Why Do Nutrients Cycle?

Unlike energy (which flows through ecosystems and is lost as heat), nutrients (chemical elements such as carbon and nitrogen) are recycled within ecosystems. The same atoms of carbon that were once part of a dinosaur could now be part of the CO2 in the atmosphere or the glucose in a plant.

Nutrient cycling involves:

• Living organisms (biotic processes)
• The abiotic environment (atmosphere, water, soil, rocks)
• Decomposers (bacteria and fungi that break down dead organic matter)

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The Carbon Cycle

Carbon is a fundamental element of life -- it forms the backbone of all organic molecules (carbohydrates, lipids, proteins, nucleic acids). The carbon cycle describes how carbon moves between the atmosphere, biosphere, hydrosphere, and lithosphere.