The Carbon Cycle

The carbon cycle describes how nature reuses carbon atoms. It is a complex cycle that involves many living organisms.

Carbon is mostly split between five stores, which include:

  • The air – as carbon dioxide (CO2)
  • Soil – which contains a lot of microorganisms
  • Fossil fuels – Deep underground
  • Animals – Stored in biological molecules
  • Plants – Stored in biological molecules

Now, let’s look at how carbon moves between the different stores.

Let’s look at some of the main processes involved in the carbon cycle.

Processes Involved in the Carbon Cycle

Removing carbon dioxide from the atmosphere

During photosynthesis, plants and algae absorb carbon from the air in the form of carbon dioxide and convert it into glucose, which can be turned into carbohydrates, proteins and fats.

Carbon moves up the food chain

The carbon locked inside plants can be passed back into the atmosphere through respiration. This is the process of breaking down organic matter to produce energy. The equation for respiration is:

Glucose + Oxygen Water + Carbon dioxide

The carbon can also be passed on to animals and microorganisms when they eat plants and algae. The carbon from the plants or algae will be stored in the animals as biological molecules, such as carbohydrates, proteins and fats. If an animal eats another animal, they get the carbon from its food too.

Animals eat the plants, algae or other animals and then they respire, which releases carbon dioxide.

Decomposition in the carbon cycle

When plants and animals die, two things can happen:

1. Animals eat the dead organism and carbon dioxide is released when the animals respire. However, the dead organisms can be eaten by decomposing organisms (that live in regions of the soil that are warm, moist and have a large amount of oxygen).

This process breaks the organisms down into smaller pieces. Eventually, all of the trapped carbon will be released as carbon dioxide, during microbial respiration.

2. Sometimes, the dead organisms are decayed in conditions where there is a shortage of oxygen. Over millions of years and significant pressure, their bodies can be converted into fossil fuels, such as:

  • Oil
  • Natural
  • coal

Humans burn fossil fuels and release carbon dioxide in the process.