Nutrient Cycles: Recycling in Ecosystems, The Carbon and Nitrogen Cycles

Edited by Jamie (ScienceAid Editor), Taylor (ScienceAid Editor), Sim, Jen Moreau and 3 others

Nutrients are chemicals necessary in any ecosystems for organisms to effectively grow, survive and decompose. A nutrient cycle is the perpetual movement of nutrients from the physical environment into a living organism and then recycled back into the physical environment. The health and stability of any ecosystems and the organisms that exist within it is highly dependent on a balanced and table nutrient cycle. Nutrient cycles involve both living and non-living contributors and include biological, environmental and chemical processes and interactions. The nutrients most utilized in ecosystems are non-mineral nutrients such as carbon, hydrogen, and oxygen. Macronutrients are also vital to ecosystems and include Nitrogen, Phosphorus, Potassium, Calcium, and Magnesium. The role of each nutrient in the cycle is dependent on the geology, the biological capabilities of the organisms, the chemical processes and reactions.

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Recycling in Ecosystem

Like energy, nutrients involved in nutrient cycles are never lost or wasted from the cycle. Excess nutrients are stored in different forms such as fossil fuels, living organisms or CO 2. A very important role played by microorganisms is that they feed on dead material by saprotrophic nutrition, converting complex organic molecules to simple ones. This conversion is a critical part of recycling, enabling ongoing movement and dispersing of nutrients across the ecosystem.

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The Carbon Cycle

All life is based on carbon; it is contained in proteins, carbohydrates; indeed all organic molecules contain carbon. So it is the most important nutrient in an ecosystem. The carbon cycle involves several stages of carbon being fixed (incorporated as part of) by plants from the atmosphere. This carbon is transferred to consumers by eating, or it becomes fossil fuel in fossilisation.

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Below is an example of a carbon cycle. They cycles can be represented a number of ways, and this is just one example.

Although much is said about rising carbon dioxide in the atmosphere, only 0.04% of air is CO2, indeed most is in the ocean as hydrogen carbonate (HCO3-), and this is where most photosynthesis occurs. That isn't to say carbon dioxide rising in the atmosphere isn't a very important global problem, just that it only comprises a small aspect of our atmosphere.

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There are two steps which are mentioned more than once; these are:

  1. 1
    All organisms do this and it converts carbohydrate to carbon dioxide.
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  2. 2
    Death and Decay
    When organisms die, their nutrients are recycled by decomposers.
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Nitrogen Cycles

Nitrogen is also a very important compound for an ecosystem. Despite its abundance in the atmosphere (79% of air is nitrogen), it is often in very limited supply. This is because it is required by plants as ammonium (NH4+ or nitrate (NO3-). After carbon, nitrogen is the most important atom in organic compounds. It is particularly important in DNA, and amino acids, which make up proteins.

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Below is an example of the nitrogen cycle, which is more complicated than the carbon cycle.

There are some key processes that are primarily performed by bacteria.

Process Bacteria Explanation
Deamination Saprophytic fungi and bacteria This is the removal of an amine group and hydrogen to make ammonia. This is similar to the process where urea is made.
Nitrification Nitrifying bacteria Two processes where NH4+ is first converted to nitrite (NO2-) then nitrate (NO3-).
Nitrogen Fixation Nitrogen-fixing bacteria Here, nitrogen from the atmosphere is taken and incorporated as NH3. Legumes (bean family) have a mutalistic relationship with nitrogen-fixing bacteria which provides them with nitrate whilst the bacteria get sugar and protection. Nitrogen fixation can also occur as a result of lightening - the electricity breaks N≡N bonds from nitrogen in the air and nitrate dissolves in the rain.
Dentrification Dentrifying bacteria. This is the loss of nitrogen into the atmosphere: NO3- N2. Denitrifying bacteria are anaerobes so tend to live in oxygen starved areas, such as waterlogged soil and stagnant water.

Questions and Answers

List and explain two different methods of sustainable agriculture?

List and explain two different methods of sustainable agriculture. How does each method work why is each method beneficial for both agriculture and the environment?

Sustainable agriculture is a method that uses unwanted organic products such as small wood pieces or chips, manure of animals (animal wastes), fruit and vegetable peels, that are usually thrown away, and incorporate them and turn them into fertilizers for crops, or pest repellents or for enriching the soil. It is a very useful method in saving money and at the same time producing a better quality of crops and higher quantity.

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  • One method of sustainable agriculture can be the enrichment of soil. For example, when you bury manure of cows under piles of wood chips and leave them for a while, after some time, decomposers and worms decompose the wood chips along with the manure and turn them into a compost that is full of microorganisms. This compost can be used as fertilizer for crops. It is organic, cheap and at the same time it can improve the quality of soil and environment by producing more crops and at the same time not polluting the environment with pesticides and chemicals.
  • Another method can be pest management and control. For example, once you reintroduce the microbe that fights the diseases into the plant or the soil, then this plant or soil will be immune against the certain types of pests and microorganisms and as a result will not be affected by them. This method is very efficient because first, it eliminates the use of chemical fertilizers which are unhealthy for the consumers of these crops, and also very efficient in yielding higher quantity and better quality.
  • A third method can be rotation of crop. For example, planting different crops and rotating each year from one type of plant to the other, such as when you plant legumes the first year, these legumes enrich the soil with nutrients that can be used the following year to yield better crops of another type that consume these nutrients.
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Yes how does the nitrogen cycle help recycle nutrients?

Nitrogen cycle recycling nutrients in the environment

  • Once inorganic nitrogen penetrates the soil (from the atmosphere), it is absorbed by a certain type of bacteria that are found in the nodules of leguminous plants.
  • These bacteria convert the inorganic nitrogen to an organic compound (such as protein, DNA, etc.)
  • The organic molecules are then released into the soil to be used by other plants, animals, and humans for survival and build up of other proteins.
  • When these organisms die, they will be degraded (with the help of the decomposers) and ammonia will be produced.
  • This ammonia will then be absorbed once again by the leguminous plants and the process will continue.
  • This is how nitrogen cycle will recycle nutrients.
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Four factors which assist in the recycling of nitrogen?

What are four named processes which assist in recycling nitrogen in the ecosystem

This question is answered in this article. See the chart under the heading "NItrogen Cycle" for an explanation on the four processes involved in nitrogen recycling.

Referencing this Article

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Categories : Ecology

Recent edits by: vcdanht, SarMal, Jen Moreau

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