Nitrogen Cycle. You know that carbon, hydrogen, oxygen and nitrogen are important nutritive elements of food substances

Carbon Cycle

You know that carbon, hydrogen, oxygen and nitrogen are important nutritive elements of food substances. Organic substances are formed by the combination of these elements in different proportions. In the cyclic movements of materials in nature, these elements which are the building units of the organic substances have an important role. Carbon is the basic element of the organic compounds. Let us notice the cyclic flow of the carbon in nature.

After observing the table given below, explain how the flow of carbon completes through the plants and animals.

Carbon Compounds and its Decomposition Process
Source		Utilization		Consumer		Decomposition process
CO2 in the atmosphere		Plants – Photosynthesis		Animals		decomposition, respiration, burning fuels

You have thus understood the role of carbon cycle in maintaining the constancy in the measure of carbon contents to an extent.

Which gas is present in abundance in the atmosphere? No doubt it is Nitrogen, which is one of the most important elements used for the synthesis of proteins required for body building and also one of the most important constituents of nucleic acids.

It is not possible to absorb free N2 directly from the atmosphere by the plants unlike the direct absorption of CO2 and O2. The atmospheric nitrogen is converted into its absorbable form as nitrates. This process is called nitrogen fixation.

Go through Illustration IV and study different ways through which N2 is converted in to nitrates. In addition to this, use of chemical fertilizers also increases the nitrate content in the soil.

Plants absorb the soil nitrates and use it for the biosynthesis of protein. This protein is transferred through the food chains. Observe the diagrammatic representation V and study the N2 cycle.

· Prepare a table showing the types of bacteria involved in the N2-cycle and their various roles.

· Prepare a brief note after detailed discussion of the question how nitrate absorbed by the plants returns to the atmosphere.

You have realized the role of N2-cycle in maintaining the constancy of atmospheric nitrogen content.

Дата добавления: 2014-12-29