During the nitrogen cycle, atmospheric nitrogen (N2) is fixed, or converted into a usable nitrogen-containing compounds called nitrates, by certain types of microorganisms. Plants can then absorb the nitrogen compounds from the soil and use it to form chlorophyll and other important biological building blocks. Consumers must obtain nitrogen from the organisms they consume. Herbivores receive their nitrogen from the plants that they eat, and carnivores get their nitrogen from the animals they consume. However, all organisms depend on the ability of nitrogen-fixing microorganisms to convert atmospheric nitrogen into a form of nitrogen that plants can assimilate, or take in and use. Finally, nitrogen is returned to the atmosphere through the combustion of fossil fuels or when decomposers break down the nitrogen found in fertilizers, urine, and dead plants and animals. Carbon-Oxygen Cycle
Carbon and oxygen are necessary for all organisms. These elements move between producers, consumers, and the atmosphere in a continuous biogeochemical cycle.
The carbon and oxygen cycles are sometimes discussed separately. However, these cycles can also be addressed together since they are dependent upon each other for proper operation. This combined, interdependent cycle is known as the carbon-oxygen cycle. There are several processes that either store carbon dioxide or release it into the environment.
Processes that Release Carbon Dioxide into the Atmosphere
Cellular respiration is a natural process in which substances are broken down to create energy.
Decay is a natural process in which organic matter, like dead organisms, decomposes or breaks down.
Volcanic activity is a natural process involving the eruption of hot gases and rock material from within the Earth.
Weathering is the process by which stones at the Earth's surface are broken down, either physically or chemically.
Degasification is the release of carbon dioxide, once dissolved in water, into the air. It is a natural process, but it has increased due to higher global temperatures. Warm water can hold less dissolved gases than cooler water. This is why a can of soda goes flat when it gets warm
Combustion is a reaction in which a substance burns in oxygen.
It can be natural, such as a forest fire started by lightning.
It can be man-made, such as burning wood and fossil fuels.
Processes that Store Carbon Dioxide
Photosynthesis is a natural process in which carbon dioxide and water are converted into sugar.
Sedimentation is a natural process in which pieces of rock and other matter settle out of water and are buried.
Dissolution is a natural process in which carbon dioxide from the atmosphere dissolves into water.
Photosynthesis & Respiration
The two most important natural processes that drive the carbon-oxygen cycle are photosynthesis and cellular respiration. Each of these processes must take place in order for the cycle to function properly. This is because the end products of one process are starting materials for the other. The black arrows represent the flow of oxygen and carbon dioxide due to cellular respiration. The magenta arrows represent the flow of gases due to photosynthesis.
Photosynthesis:
carbon dioxide + water → sugar + oxygen
The end products of photosynthesis are sugar and oxygen. These substances are the starting materials of cellular respiration.
Cellular Respiration:
sugar + oxygen → carbon dioxide + water
The end products of cellular respiration are carbon dioxide and water. These substances are the starting materials of photosynthesis.
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