4.1 The Carbon Cycle
Carbons is present is pretty much everything in the world. It is present in all living thing, it is part of the ocean, it is in air and it makes up rocks. Carbon does not stay in one place and instead it is recycled through various processes, which is known as the carbon cycle. Carbon moves through the carbon cycle in 3 different ways:
- Removing carbon from the atmosphere
- Carbon is present in the atmosphere in the form of carbon dioxide. Carbon dioxide (CO2) is removed from the atmosphere by photosynthesis, which is undertaken by plants. (The equation for photosynthesis is: carbon dioxide + water [+ light energy ] -> glucose + oxygen). After photosynthesis, the carbon that was present in carbon dioxide becomes part of complex molecules in the plants, such as proteins, fats and carbohydrates. - Passing carbon from one organism to the next.
- Animals eat plants in the environment. The carbon that is present in the proteins, fats and carbohydrates in the plants that is being eaten is passed on to the animal that is eating the plant. Also, carbon moves on again when these animals are eaten by animals above them in the food chain. Carbon therefore moves through the food chain - Returning carbon to the atmosphere (carbon is usually returned to the atmosphere in the form of carbon dioxide)
- Carbon is returned to the atmosphere through the respiration from animals, microorganisms and plants (remember that plants respire all of the time). It is released into the atmosphere in the form of carbon dioxide (respiration is: glucose + oxygen -> carbon dioxide + water [+ energy]).
- The combustion of woods and fossil fuels returns carbon to the atmosphere in the form of carbon dioxide. Carbon dioxide levels in the atmosphere have increased significantly because of the world’s addiction to burning fossil fuels.
- The decay and decomposition of dead and waste material (e.g.) leads to carbon being returned into the atmosphere. This happens because the microorganisms and detritus feeders that cause the decay respire. After the microorganisms and detritus feeders have finished breaking down the waste products and dead bodies of organisms in the ecosystem, the nutrients is passed onto plants and algae that grow in the soil.
- Volcanic eruptions result in carbon being returned to the atmosphere.
Fossil Fuels
When an organism has died, their body usually decay. During decay, carbon is returned to the atmosphere in the form of carbon dioxide through the respiration of the decomposers that are decaying the dead material. Over millions of years, some of the dead materials from animals and plants may become fossil fuels (e.g. oil). These fossil fuels store carbon until they are burnt, which results in the carbon dioxide being returned to the atmosphere in the form of carbon dioxide.
When an organism has died, their body usually decay. During decay, carbon is returned to the atmosphere in the form of carbon dioxide through the respiration of the decomposers that are decaying the dead material. Over millions of years, some of the dead materials from animals and plants may become fossil fuels (e.g. oil). These fossil fuels store carbon until they are burnt, which results in the carbon dioxide being returned to the atmosphere in the form of carbon dioxide.
Carbon Cycle and the Sea
Marine animals convert some of the carbon that is in their diet into calcium carbonate (CaCO3), which is then used to make their shells. When the marine animals with shells die, their shells collect at the bottom of the sea where they form limestone.
Marine animals convert some of the carbon that is in their diet into calcium carbonate (CaCO3), which is then used to make their shells. When the marine animals with shells die, their shells collect at the bottom of the sea where they form limestone.