The Carbon Cycle

The carbon cycle describes the movement of carbon atoms through various reservoirs and processes in the environment.

Interactions between Earth systems6–8% of exam

Understand It

Ace It

Context

What this topic is and why it exists

The carbon cycle involves carbon atoms moving through the atmosphere, biosphere, hydrosphere, and lithosphere.

Photosynthesis and cellular respiration are crucial processes here.

In photosynthesis, plants convert atmospheric CO2 into organic matter, which travels through food webs.

Cellular respiration by plants and animals returns CO2 to the atmosphere.

Carbon storage varies: oceans absorb CO2, forming bicarbonates; forests store carbon in biomass; soil contains carbon as organic matter.

Fossil fuels represent long-term carbon storage, formed from ancient organic matter.

When burned, they release CO2 quickly, disrupting the cycle.

The trap is thinking of reservoirs as equal in stability or size.

They are not.

Oceans and forests are massive but slow to change; atmospheric carbon is small but volatile.

Misjudging this scale leads to errors in predicting climate impacts.

Fossil fuel combustion accelerates the cycle, pushing more carbon into the atmosphere than natural processes can handle.

This imbalance drives climate change, illustrating the feedback loop central to AP Environmental Science.

Recognize this cycle's dynamics to understand carbon's role in global systems.

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