Nitrogen Cycle

An element needed for all life on Earth is nitrogen. In fact, about 78% of the atmosphere is made up of nitrogen, and it makes up about 3% of your body weight. However, most nitrogen in the air is not usable by plants and animals, so it must be changed into different states. The conversion of the nitrogen into something useful for animals and plants is the foundation of the nitrogen cycle.

Just like water moves between the Earth and its atmosphere, nitrogen moves between plants, animals, bacteria, the air, and soil in the ground. It is the basis of the nitrogen cycle. Nitrogen is used in plants help them to grow faster, but too much of it can cause acid rain.

The nitrogen in the air cannot be used directly by plants or animals. Animals need nitrogen to make proteins, and plants need it to make chlorophyll, which is necessary for photosynthesis (the process plants use to make their own food). Animals receive the nitrogen by eating plants or when they eat other animals. Nitrogen in plants and animals is needed to grow and to create DNA.

The nitrogen cycle is a continuous process and includes several steps. The process begins as nitrogen in the atmosphere is introduced into the soil by precipitation. During the first step, fixation, the nitrogen bond is broken. Bacteria in the soil changes nitrogen into ammonium, a chemical derived from ammonia. It can also be broken by lightning. It is still unsafe for plants, so it must be converted. During fixation, the nitrogen is combined with oxygen or hydrogen.

Next, during nitrification, the ammonium gets changed or converted first into nitrites and then into nitrates by a different bacterium. The nitrates can then be absorbed by the plants. The plants build up proteins. Third, during assimilation, the plants absorb the nitrates from the soil into their roots, and the nitrogen gets used in amino acids, nucleic acids, and chlorophyll.

The fourth step, ammonification, begins when animals eat the plants, they use it to build protein too. As the animals either poop, pee, or die, waste is broken down by decomposers. The nitrogen is re-introduced into the soil in the form of ammonia.

Finally, during denitrification, the extra nitrogen in the soil can be put back into the air as a gas. Special bacteria help with this process as well. The cycle repeats itself once the nitrogen returns to the atmosphere. Without bacteria in the cycle, the nitrogen could not be converted for use by plants or animals.

All organisms rely on the nitrogen cycle to live and survive. However, if an organism receives too much or too little nitrogen, it will be negatively affected. As with each of the cycles of the Earth, they can be affected by human behavior. The nitrogen cycle problems can be affected in three ways:

Nitrogen fertilizer: human-made fertilizer is used on plants throughout the world causing additional nitrogen to be added to ecosystems everywhere.

Deforestation: The trees and other plants in forest help retain the nitrogen in the atmosphere. When the forests are cleared, the amounts of nitrogen in the air and wetlands increase.

Fossil fuel burning: Burning fuels such as coal, gas, etc., increase the amount of nitrogen in the atmosphere.

Since human behavior can cause problems with the nitrogen cycle, the problems can be diminished by changing behavior. People can try to use natural fertilizer, such as available through composting; support environmental organizations, and walk or bike instead of using a car. The nitrogen cycle is vital for all living organisms today and in the future.




A: 87%
B: 3%
C: 78%
D: 50%

A: Fixation
B: Nitrification
C: Assimilation
D: Denitrification

A: Ammonia
B: Decomposers
C: Nitrites
D: Nitrates

A: Bacteria
B: Nitrates
C: Ammonia
D: Nitrites

A: Fertilizer
B: Deforestation
C: Precipitation
D: Fossil fuel burning

A: DNA
B: Genes
C: Oxygen
D: All the above








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