Carbon Cycle
[All life is based on the element carbon. Carbon is the major component of most organic matter, from fossil fuels to the complex molecules (DNA and RNA).
Organic matter – the matter that contains atoms of Carbon, and that has come from the remains of once-living organisms
Yet by weight, carbon is not one of the most abundant elements in the Earth's crust. In fact, the lithosphere is only 0.032% carbon by weight. In comparison, oxygen and silicon respectively make up 45.2% and 29.4% of the Earth's surface rocks]
Carbon Cycle – exchange of Carbon atoms between living organisms, dead organisms, the atmosphere, oceans (hydrosphere), rocks and soil (lithosphere)
It is called a cycle because Carbon eventually comes back from where it has come.
In the CD, the following abbreviations are used: PS (photosynthesis), R (respiration), C (in black: combustion; in blue: carbon), i (ingestion), d (decomposition), D+W (dead + waste)
Methods of taking Carbon from the atmosphere:
1)Carbon enters the Biosphere duringPhotosynthesis:
Picture 1
Photosynthesis is a process in which green plants (producers) make carbohydrate food (glucose) with the help of chlorophyll pigments by using carbon dioxide, water and sunlight
6CO2+ 6H2O+ sunlight = C6H12O6+6O2
Picture 2
Some carbon dioxide enters water via algae and phytoplankton through the process of photosynthesis
2)Carbon Consumption:
Animals and people are non-photosynthetic creatures. That means, they are not able to create their own food.
Instead, they eat plants (which acquired carbon through photosynthesis), or other animals (which ate plants before).
That is how animals and people (consumers) get carbon into their bodies(Picture 1)
3)Carbon gets into Hydrosphere, too
Picture 2
Carbon dioxide is slightly water-soluble and is absorbed by oceans, seas, and lakes through the water surface (by the process called “diffusion”)
Some carbon dioxide enters water via algae and phytoplankton through the process of photosynthesis
4)Carbon gets into Lithosphere, too
Picture 2
Marine organisms such as corals and those with shells (snails, pearls, etc.) take up carbon dioxide from the water and convert it into calcium carbonate (CaCO3). As the shelled organisms die, bits and pieces of the shells fall to the bottom of the oceans and accumulate as sediments
Picture 1
Non-marine organisms produce waste or eventually die, which introduces carbon into the ground (lithosphere)
Any organic material, which is not broken down by decomposers, turns into fossil fuels
Fossil Fuels were formed very long time ago from plant or animal remains that were buried, compressed, and transformed into oil, coal, or natural gas. The carbon contained in the fossils is said to be "fixed" in place and is essentially locked out of the natural carbon cycle
Methods of releasing Carbon back into the Atmosphere:
1)Respiration/ Metabolism [Pictures 1, but could happen in water]
These processes occur in all living organisms that require energy to grow or move, such as plants, animals, fish, and humans. In the cells, a series of complex reactions occurs with oxygen to convert food (glucose) into carbon dioxide and water and ENERGY
C6H12O6 + O2 → CO2 + H2O + energy
2)Decomposition/Decay [Picture 1 but could happen in water]
Similar reaction is also carried out by decomposing bacteria during the Decomposition (Decay) of waste materials on land and in water
C6H12O6 + O2 → CO2 + H2O + energy + nutrients (Compare the equation with that of respiration)
3)Combustion [Pictures 1 and 2]
This occurs when any organic material reacts (burns) in the presence of oxygen to give off the products of carbon dioxide and water and ENERGY. The organic material can be, for example, any fossil fuel.Arguably, the combustion of fossil fuels is not considered to be a part of the “natural” carbon cycle, since it is done by humans. Burning of biomass (ex: forest fires, wood used for heating, etc.) can also transfer substantial amounts of carbon into the atmosphere. Forest fires happen naturally, so that combustion is part of “natural” carbon cycle
CH4(natural gas) + O2 → CO2 + H2O + energy
4)Raised sediments [Picture 2]
Through tectonic activities, over long periods, the sediments built up at the bottom of oceans may be raised up as dry land or into mountains. This type of sedimentary rock is called limestone (CaCO3 + other minerals). The carbonates from the limestone can redissolve (that is, dissolve again) in air and rainwater, releasing carbon dioxide back into the air (atmosphere) or water bodies (hydrosphere)
5)Volcanic Activities [Picture 2]
Volcanic eruptions release gases into the atmosphere. Volcanic gases are primarily water vapor, carbon dioxide and sulfur dioxide
Carbon Imbalance
The uptake and return of CO2back into atmosphere are currently not in balance (not equal to each other). The carbon dioxide content of the atmosphere is gradually and steadily increasing. Since CO2is a greenhouse gas,the consequence is global warming
Study Guide: P. 9 – 11
Textbook: P. 254 – 257, 280 (# 1 – 3)