DAUR NITROGEN (N)

Summary

The video explains the nitrogen cycle, highlighting how nitrogen, the most abundant element in the atmosphere, is essential for life but can't be directly used by organisms. It covers the processes of nitrogen fixation by lightning and microorganisms like *Rhizobium*, decomposition of dead organisms releasing nitrogen, and nitrification, where ammonium is converted into nitrates. The video also explains denitrification, where nitrogen is released back into the atmosphere when oxygen is scarce. This cycle is crucial for plants to access nitrogen, enabling them to produce food and maintain ecosystems.

Takeaways

• 😀 Nitrogen is the most abundant element in Earth's atmosphere, making up 80% of it.
• 😀 Organisms cannot directly take nitrogen from the air due to the high energy required to break nitrogen molecules apart.
• 😀 Lightning provides the necessary energy to break nitrogen and oxygen molecules, forming compounds like NO2 and NH2.
• 😀 Nitrogen compounds from lightning react with rainwater, which helps fertilize the soil.
• 😀 Certain microorganisms, such as Rhizobium, can bind nitrogen from the air and form symbiotic relationships with leguminous plants, enriching the soil.
• 😀 Other soil bacteria, such as proteobacteria, can also fix nitrogen from the atmosphere.
• 😀 The process of nitrogen fixation by bacteria is crucial in supplying nitrogen to the soil, either directly or through ammonification.
• 😀 Decomposing plant and animal matter releases nitrogen in the form of amino acids and proteins, which are broken down by decomposers into ammonium.
• 😀 Ammonium can be absorbed by plants, but most of it is utilized by aerobic bacteria as an energy source.
• 😀 Ammonium undergoes nitrification by bacteria, first converted into nitrite by Nitrosomonas and then into nitrate by Nitrobacter, which plants can use.
• 😀 Nitrification only occurs in the presence of sufficient oxygen, as it involves aerobic bacteria.
• 😀 When oxygen is limited, denitrification occurs, releasing nitrogen back into the atmosphere as soil bacteria use nitrate as an oxygen source.

Q & A

What is the most abundant element in the atmosphere?

Nitrogen is the most abundant element in the atmosphere, making up 80% of its composition.

Why can't living organisms directly use nitrogen from the air?

Living organisms cannot directly use nitrogen from the air because it requires a large amount of energy to break the nitrogen bonds in its molecular form.

How is nitrogen broken down in nature?

Nitrogen is broken down through the energy provided by lightning. The high energy from lightning triggers a reaction between nitrogen and oxygen to form compounds such as NO2 and NH2, which then fall to the earth with rain.

What is the role of Rhizobium in nitrogen fixation?

Rhizobium is a microorganism that forms a symbiotic relationship with the roots of leguminous plants, helping fix nitrogen from the air into a form that plants can use, enriching the soil.

What other bacteria can fix nitrogen, besides Rhizobium?

Other bacteria groups, such as soil bacteria from the Proteobacteria family, can also fix nitrogen from the air.

What is ammonification and how does it work?

Ammonification is the process of converting organic nitrogen from dead organisms into ammonium (NH4+). Decomposers like detritivores break down dead organisms into detritus, which is then processed into ammonium.

Can plants directly absorb ammonium?

Plants can absorb ammonium, but only a small portion of it is taken up, as most ammonium is used by aerobic bacteria as an energy source.

What is nitrification, and how does it occur?

Nitrification is the process in which ammonium is converted into nitrite (NO2-) by Nitrosomonas bacteria, and then nitrite is further converted into nitrate (NO3-) by Nitrobacter bacteria. Nitrate is then available for plants to absorb.

Why is oxygen necessary for nitrification?

Oxygen is required for nitrification because the bacteria involved in this process are aerobic, meaning they rely on oxygen to convert ammonium to nitrite and nitrite to nitrate.

What happens during denitrification, and why does it occur?

Denitrification occurs when soil lacks sufficient oxygen. In this process, denitrifying bacteria convert nitrate back into nitrogen gas (N2), which is then released into the atmosphere, completing the nitrogen cycle.