The Carbon Cycle

The carbon cycle

Transfer of carbon from one store to another.

Which forms is carbon present in?

Organic carbon found in the biomass of living organisms

Inorganic carbon found in the atmosphere and the ocean

What are the main carbon stores or sinks?

Ocean, fossil fuels, and living organisms.

What are the four pools between which carbon moves?

Biosphere, hydrosphere, atmosphere, and sediments by fluxes

Carbon transfer (fluxes)

Dissolving, combustion or photosynthesis

Diffusion

CO2 diffuses form the atmosphere or water into autotrophs

Photosynthesis

Autotrophs convert CO2 from the atmosphere into carbohydrates and other organic compounds

Respiration

CO2 is produced as a waste product and diffuses out into the atmosphere or water

Decay

Dead organic matter is decomposed to CO2, water, ammonia and mineral ions by organisms

Peat

Forms when plant matter doesn’t fully decompose due to acidic and anaerobic conditions

When does peat release carbon?

When exposed to oxygen or burned.

Combustion

Releasing of carbon dioxide when burning fossil fuels and organic material

Feeding

Gaining carbon compounds from other organisms

What does biomass, peat, coal, oil, and natural gas from big carbon sinks release when burned?

Carbon dioxide and water in complete compustion

What is formed over a large period of time?

Oil and gas from dead marine organisms containing calcium carbonate.

How is oil and gas formed from marine organisms?

By heat and compression over time.

What has coal been formed from?

Plant material

What is the first stage in coal formation?

Peat

What is formed when sediments accumulate over partially decomposed peat?

Coal by further transformation through weight and pressure

What does the majority of carbon dioxide emission from combustion originate from?

The burning of fossil fuels by humans

What occurs if photosynthesis exceeds respiration in an ecosystem?

There is a net uptake of carbon, making the ecosystem act as a carbon sink.

What occurs if respiration exceeds photosynthesis in an ecosystem?

There is a net release of carbon, making the ecosystem act as a carbon source.

What can be said about the rate of these two processes?

They are not necessarily equal

What are the components of carbon cycle diagrams?

Storages represented by boxes and fluxes represented by arrows.

Why are fossil fuels non-renewable?

Because they take millions of years to form under specific conditions.

What happens when carbon stored in fossil fuels is burned?

CO2 is released, increasing atmospheric carbon levels.

When does an ecosystem act as a carbon sink?

When photosynthesis exceeds respiration (net carbon uptake).

When does an ecosystem act as a carbon source?

When respiration exceeds photosynthesis (net carbon release).

How are carbon cycle diagrams constructed?

Pools are drawn as boxes, fluxes as arrows.