Nitrogen Cycle and Its Importance

The video explains the nitrogen cycle, highlighting the 78% nitrogen composition in the atmosphere and its importance for living organisms. It describes nitrogen fixation by bacteria and lightning, how plants absorb fixed nitrogen for protein synthesis, and the role of decomposition in recycling nitrogen back into the atmosphere, maintaining a constant nitrogen level.

What percentage of the Earth's atmosphere is composed of nitrogen?

• 50%

• 78%

• 33%

• 21%

Why is nitrogen essential for living organisms?

• It is a part of proteins, chlorophyll, nucleic acids, and vitamins

• It helps in respiration

• It is used in photosynthesis

• It is a source of energy

Which organisms are capable of converting atmospheric nitrogen into usable compounds?

• Viruses

• Fungi

• Rhizobium and blue-green algae

• Insects

Where does Rhizobium bacteria live?

• In the leaves of plants

• In the root nodules of legume plants

• In the flowers of plants

• In the stems of plants

How can nitrogen be fixed apart from bacterial action?

• Through evaporation

• Through lightning

• Through respiration

• Through photosynthesis

How do plants absorb nitrogen from the soil?

• Through their stems

• Through their flowers

• Through their roots

• Through their leaves

What happens to nitrogenous compounds when plants and animals die?

• They evaporate

• They are absorbed by other plants

• They are converted and decomposed by bacteria and fungi

• They remain unchanged in the soil

How does the percentage of nitrogen in the atmosphere remain constant?

• Through the action of fungi

• Through the action of animals

• Through the action of plants

• Through the recycling of nitrogen by bacteria