Carbon cycle

Joanna George-Johnson, Contributor

For most students, this is the second most feared topic in biology, next to the nitrogen cycle (the nitrogen cycle is coming next).

Reading ahead allows students to keep pace with the hectic nature of school. Here, a Penwwod High School student is in deep concentration as she reads from a textbook, recently. -Anthony Minott Freelance photographer

Carbon is an extremely important element to life. All living things are composed of carbon. For this reason, it is necessary to study the cycle of carbon in the environment.

Carbon molecules take many forms. Some are a part of organic molecules and others are a part of inorganic molecules.

Here are some useful terms that are needed for you to understand the carbon cycle.

Terminology

Combustion: Burning of carbon-based materials (e.g., wood, gasoline, coal) to obtain energy to do work, releasing CO2 as a by-product.

Humification: The alteration of organic matter that is too complex to be broken down by bacteria and fungi. This carbon becomes part of the matter in the soil.

Inorganic: Molecules that are not of biological origin (e.g., CO2, bicarbonate).

Organic: Molecules that are of biological origin (e.g., wood, leaves, sugars, starches).

Organic matter: Various molecules and pieces of dead tissue that are of biological origin.

Photosynthesis: The conversion of carbon dioxide into sugars by plants, using the sun as an energy source.

Respiration: The conversion of sugars into carbon dioxide to release energy.

Outline of the carbon cycle

Two main things to consider when looking at the carbon cycle are:

1. How does the carbon get incorporated into the living world?

2. How does the carbon get released into the atmosphere?

Incorporating carbon into the living world

Although carbon is essential for all living things, animals such as us cannot use the carbon directly found in the atmosphere. That is carbon dioxide.

Plants, however, can use the carbon dioxide found in the atmosphere, with the help of other molecules and the sun, to make carbohydrates. So, by the process of photosynthesis, plants incorporate the carbon from carbon dioxide into their structure.

When animals eat the plants, they in turn incorporate the carbon into their structure. So this is how carbon from the atmosphere gets incorporated into the living world.

Some of the carbon dioxide is also dissolved in our waterways.

The amount of carbon in the biosphere is always the same. Therefore, just as it gets incorporated into the living world, there must be a way for it to be released into the atmosphere as carbon dioxide gas.

Releasing carbon into the atmosphere

Carbon is released into the atmosphere through the following ways:

1. When animals respire, they release carbon dioxide. This is exhaled by mammals.

2. Plants also respire and release carbon dioxide into the atmosphere.

3. When plants and animals die, the part of their bodies that were not completely decomposed will, over time, be converted into what is known as fossil fuels. When these fuels are burned to run our cars and stoves and power plants for electricity, carbon will be released as carbon dioxide. This process is called combustion (burning).

4. Volcanoes are also a source of releasing carbon dioxide to the atmosphere. These processes are continuous, so as carbon is taken from the atmosphere, carbon is released through other means. Therefore, the carbon is always cycled through the biosphere.

From the explanation above complete the diagram at the top left. Use the following words: fuels, combustion, animal respiration, photosynthesis, dissolving, plant respiration.

Joanna George-Johnson teaches at Ardenne High School.
Email: Masterbio@gmail.com.