The two biological processes that are key to carbon cycling are photosynthesis and respiration.
Photosynthesis is carried out mainly by green plants, algae, and certain bacteria. These organisms take in carbon dioxide from the atmosphere and, using sunlight as energy, convert it into glucose and oxygen. This process is fundamental because it is the primary way that carbon is removed from the atmosphere and incorporated into living organisms.
On the other hand, respiration is a process performed by almost all living organisms, including plants, animals, and microorganisms. During respiration, these organisms break down glucose and other organic materials to release energy, resulting in the production of carbon dioxide as a byproduct. This carbon dioxide is then released back into the atmosphere, completing the carbon cycle.
In summary, while photosynthesis sequesters carbon from the atmosphere, respiration returns it, and together these processes maintain the balance of carbon in our ecosystem.