Nitrogen Cycle

Question 1 Explain nitrogen cycle in atmosphere?

Question 2 Define nitrogen cycle?

• NCERT Solutions Class 8 Science

Nitrogen Cycle

Nitrogen is required by both, plants and animals for their growth and development.

It is an essential component of proteins which make up the bodies of plants and animals.

It is also present in chlorophyll, nucleic acid and vitamins.

The circulation of nitrogen elements through living things and non-living environment is called nitrogen cycle in nature.

1)The atmosphere contains nitrogen gas. The nitrogen fixing bacteria(present in the soil and in the root nodules of leguminous plants),blue green algae and lightning in the sky nitrogen gas from the atmosphere and convert it into compounds of nitrogen which go into soil.

2)The plant take compounds of nitrogen from the soil for their growth. The plants absorb the nitrogen compounds from the soil through their roots. The plants convert the compounds of nitrogen into plant proteins and other organic compounds which make up the body of plants.

3)The plants are eaten up by animal as food. Animals convert plant protein into animal protein and other organic compounds which make up their body. Some animals also eat other animals to obtain nitrogen compounds.

4)When plants and animals die, the complex nitrogen compounds present in their dead bodies are decomposed and converted into simple compounds of nitrogen by certain bacteria and fungi present in the soil. All the simple compounds of nitrogen formed in this way go into the soil. The compounds of nitrogen which were taken by the plants from the soil during their growth are returned to the soil. These nitrogen compounds are again absorbed by the new plants for their growth and this part of nitrogen cycle is repeated endlessly.

5)Some of the compounds of nitrogen are decomposed by denitrifying bacteria present in the soil to form nitrogen gas. The nitrogen gas goes back into the atmosphere.

Other Notes from Chapter 2 Micro Organisms Friend and Foe

• Micro-Organisms
• Groups of Micro Organism
• Where do Micro Organism Live
• Useful Micro organism
• Making of Curd and Bread
• Commercial Use of Micro organism
• Medicinal Use of Micro oragnaism
• Increasing Soil Fertility
• Cleaning the Environment
• Harmful Micro Organism
• Carriers of Disease causing micro organism
• Disease Causing Micro organisms in Animals
• Disease Causing Micro-Organism in Plants
• Food poisoning
• Preservation of Food
• Preservation by sun-drying, Heating, Cooling
• Preservation by Deep Freezing,Common Salt, Sugar
• Preservation of food by mustard oil and Vinegar, Chemicals, Pasteurisation, Air-tight Packets
• Nitrogen Fixation