Nitrogen Cycle | Natural Resources | Assessment | English | Grade 9

The biochemical cycle through which nitrogen is circulated in various forms in our environment is called ______

• Nitrate cycle

• Nitrite cycle

• Nitrogen cycle

• None of these

Answer explanation

The biochemical cycle through which nitrogen is circulated in various forms in our environment is called nitrogen cycle.

What is true about Rhizobium?

• It is a free-living bacteria.

• It lives in root nodules of leguminous plants.

• It converts nitrate into nitrogen gas.

• All of the above

Answer explanation

Rhizobium live in root nodules of leguminous plants and maintain symbiotic relationship with the plants.

Which of the following stage is not involved in nitrogen cycle?

• Nitrogen fixation

• Respiration

• Denitrification

• Ammonification

Answer explanation

Various stages of nitrogen cycle are Nitrogen Fixation, Assimilation, Ammonification, Nitrification, and Denitrification. Respiration is not involved in nitrogen cycle.

What is the percentage of nitrogen in the atmosphere?

• 100%

• 2%

• 78%

• 21%

Answer explanation

Our atmosphere contains 78% of nitrogen.

Process by which ammonia is converted into nitrite followed by nitrate in the soil with the help of bacteria is called

• Nitrification

• Assimilation

• Nitrogen fixation

• Ammonification

Answer explanation

Process by which ammonia is converted into nitrite followed by nitrate in the soil with the help of bacteria is called nitrification.

Which of the following bacteria oxidises ammonia into nitrite?

• Nitrobacter

• Pseudomonas

• Thiobacillus

• Nitrosomonas

Answer explanation

Nitrosomonas bacteria oxidize ammonia into nitrite. Nitrobacter converts nitrite into nitrate. Pseudomonas and Thiobacillus are denitrifying bacteria that converts nitrates back into nitrogen gas.

Choose the correct option with respect to Denitrification.

• The process by which ammonia is converted into nitrite followed by nitrate in the soil with the help of bacteria.

• The process of conversion of nitrate into nitrogen gas with the help of bacteria.

• The process of decomposition of compounds of nitrogen such as proteins, urea, etc present in the dead remains of the plants and animals into ammonia.

• The usable form of nitrogen is absorbed by the plants and used for the formation of proteins and other essential compounds.

Answer explanation

Nitrification - The process by which ammonia is converted into nitrite followed by nitrate in the soil with the help of bacteria. Denitrification - The process of conversion of nitrate into nitrogen gas with the help of bacteria. Ammonification - The process of decomposition of compounds of nitrogen such as proteins, urea, etc present in the dead remains of the plants and animals into ammonia. Assimilation - The usable form of nitrogen is absorbed by the plants and used for the formation of proteins and other essential compounds.