Nutrient Cycles, Biology tutorial


The main source of energy to the ecosystem is from the sun. The energy of sun is coupled by other natural accessible elements like oxygen, nitrogen, carbon to form a variety of materials. Such materials are constantly recycled among the living and non-living components. Some of the most significant elements in the metabolism of living organisms are nitrogen, oxygen, carbon, hydrogen, phosphorous and sulphur. Though, over one hundred elements exist however oxygen, hydrogen and nitrogen are around 99 percent of the biosphere. The major nutrients for maintenance of life are oxygen, carbon, nitrogen and water; and the cycling of such nutrients is initiated through physical, biological and chemical methods. Thus, there is need to comprehend such cycles and how subtle balance is maintained.

Nutrient cycling in nature:

Around one hundred nutrients have been recognized in nature. However the most significant one to life are oxygen, carbon, nitrogen and water. Such nutrients will form the main contents of the topic.

The Carbon Cycle:

The various sources of carbon in the abiotic environment comprise:

a) Water bodies (that is, seas, oceans and rivers).

b) Fuels (that is, petroleum), gas, coal and coke.

c) Marble, limestone and corals.

d) In dead organisms.

e) Gas, discharged from decomposers or burning of fuels.

The carbon cycle is an easy process that brings about the circulation of carbon compounds in the biosphere. The procedure of carbon cycling comprises the given:

1) Plants take out carbon from atmospheric carbon-dioxide in the presence of sunlight and water, and utilize it to form carbohydrate and sugar found in plants, all through the procedure termed as photosynthesis.

2) Carbohydrate in plants is eaten by man and animals and becomes integrated into their tissues. Whenever they pass faces, a few carbon compounds are discharged into the atmosphere.

3) When animals and plants respire, carbon-dioxide is generated from the breakdown of glucose and discharged into atmosphere.

4) When animals and plants die, fungi and bacteria initiates decay and in the procedure, locked up carbon are discharged as carbon-dioxide into the atmosphere.

5) Throughout the burning of natural gas, petroleum, coal, wood, carbon in such materials are oxidized to provide carbon-dioxide which is released into the atmosphere.

6) Calcium carbonate is employed by marine organisms to form shells; overtime, when they die, the carbon is discharged into water and ultimately into the atmosphere.

The Oxygen Cycle:

Oxygen is the other nutrient that is significant to all living things. Note that the oxygen and carbon cycles are independent but much closely associated. Oxygen is present in our atmosphere in the form of pure oxygen, water-vapor, ozone and carbon-dioxide. Plants and algae carry out photosynthesis that eliminates carbon-dioxide and adds oxygen to the atmosphere. Animals carry out cellular respiration which eliminates oxygen from the atmosphere and adds up carbon-dioxide.

Whenever animals and plants die, decomposers employ oxygen to break down the organic material and discharge carbon dioxide. As well, water dissolves oxygen and the aquatic life makes use of this oxygen for the photosynthesis and cellular respiration.

Carbon-oxygen balance:

As we all are familiar that there are two natural processes continuously occurring in the nature:

a) One is Respiration that consumes oxygen and generates carbon dioxide

b) Second is the Photosynthesis that consumes carbon-dioxide and generates oxygen.

There is generally a balance among Respiration and Photosynthesis in nature that makes amount of oxygen and carbon-dioxide almost constant in nature. The human activities usually disturb this balance that causes most of the ecological and health problems.

Nitrogen Cycle:

Nitrogen is the other significant nutrient which all organisms require. All living things require nitrogen to make proteins. Let us observe how this nutrient is recycled in the ecosystems.

Around 78 percent of the atmosphere is nitrogen. Though, neither animals nor plants can employ this form of nitrogen directly. Generally, the nitrogen should be in the form of chemicals termed as nitrate. Then the plant roots can absorb it. Lightning forms some nitrate through causing oxygen and nitrogen in the atmosphere to unite. Rhizobium bacteria can do the similar thing. These bacteria live on the roots of plants termed as legumes like peas, beans and alfalfa. Most of the bacteria and blue-green algae as well form nitrates. The modification of nitrogen to nitrates is termed as nitrogen fixation. Plants make use of the nitrates which they absorb to make plant proteins. Animals acquire the nitrogen that they require to make proteins by eating other animals or plants.

When animals and plants die, bacteria transform their nitrogen content to ammonia. The nitrogen in the urine and fecal matter of animals is as well modified to ammonia by bacteria. The pungent odor of chicken pens, outhouses, hog yards, cat litter boxes and wet baby dippers is plentiful proof of this fact. Ammonia, in turn, is transformed to nitrites and then to nitrates through bacteria. This procedure is termed as nitrification and completes the major part of the cycle.

Most of the plants are capable to employ ammonia directly. Thus all of it doesn't encompass to be transformed to nitrate before plants absorb it. If people make use of synthetic fertilizers they add nitrite or nitrate to the soil. This skips most of the nitrogen cycle and therefore the bacteria and microorganisms lose their food source. Algae and plants in the water require nitrogen to grow. A few species of fish based on these plants for food.

Water Cycle:

Water molecules modify into water-vapor and move into the atmosphere through the procedure of evaporation. The surplus water absorbed by plant roots is discharged through the pores on the surface of leaves by the procedure of transpiration.

The method by which water-vapor rises up, cools down in the high atmosphere and forms clouds is termed as condensation.

As condensation carries on, water-vapor changes into the water droplets. If adequate water droplets build up, they fall down as rain. This procedure is termed as precipitation. The rain refills the water in the ponds, lakes, oceans and other water bodies. The method of rain water therefore entering the soil is termed as infiltration. If rain water flows over the surface of land prior to entering the water bodies, it is termed as surface runoff.

At extremely low temperatures, water freezes and falls down as snow, hail and sleet.

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