Nitrogen is important to life because it is used to build the proteins and DNA that are found in every living thing. This means that without nitrogen, you would not be alive! As you can imagine, an important process in ecosystems is the recycling of nitrogen through its biotic (living) and abiotic (nonliving) parts.
If you look closely at the diagram provided above, you will notice that there are many ways in which nitrogen cycles through nature.
Atmosphereic Nitrogen: The nitrogen cycle starts where the biggest supply of nitrogen is found, in the atmosphere. Approximately 78% of the air you breathe is made of nitrogen gas. Unfortunately, like almost every other organism, we cannot actually use nitrogen gas directly – that’s where bacteria come into play.
Ammonification: Nitrogen gas from the atmosphere is fixed into organic nitrogen by nitrogen-fixing bacteria. This organic nitrogen enters terrestrial food webs. It leaves the food webs as nitrogenous wastes in the soil. Neither plants nor animals can get nitrogen directly from the atmosphere. Ammonification occurs when bacteria found in the roots of plants change nitrogen gas into a form that plants can use called ammonia. Ammonia can then be taken in by plants, so they get the nitrogen they need to survive. Ammonification of this nitrogenous waste by bacteria and fungi in the soil converts the organic nitrogen to ammonium ion—NH4+
In order to get the nitrogen they need to survive, animals must eat plants (we call these animals herbivores). Animals that do not eat plants, must eat the herbivores to get the nitrogen they need. The process of plants and animals taking in nitrogen is called assimilation. Think of assimilation as plants and animals "eating" nitrogen.
Once a plant or animal dies, it decomposes. As the decomposition occurs, the nitrogen found in the dead organism is returned to the soil. Then, a different type of bacteria, changes the useable nitrogen in the soil, back to nitrogen gas through a process of called denitrification. And the cycle starts all over again.
Nitrogen enters the living world by way of bacteria and other single-celled prokaryotes, which convert atmospheric nitrogen — N2—into biologically usable forms in a process called nitrogen fixation. Some species of nitrogen-fixing bacteria are free-living in soil or water, while others are beneficial symbionts that live inside of plants.
Prokaryotes play several roles in the nitrogen cycle. Nitrogen-fixing bacteria in the soil and within the root nodules of some plants convert nitrogen gas in the atmosphere to ammonia. Nitrifying bacteriaconvert ammonia to nitrites or nitrates. Ammonia, nitrites, and nitrates are all fixed nitrogen and can be absorbed by plants.
What percent of the air is nitrogen?
60%
70%
78%
90%
What happens to the nitrogen found in the remains of dead organisms?
It is returned to the soil
It turns into an animal
It flies away
What is assimilation?
The process of plants and animals taken in nitrogen
The loss or removal of nitrogen or nitrogen compounds specifically
Living things
Special bacteria found in the roots of plants to change nitrogen gas into a useable form
What is the major reservior of nitrogen?
Plants and animals
Soil
Oceans
Atmosphere
How does nitrogen get to the soil?
Snow
Rocks
Bacteria
Process by which ammonium is changed into nitrates by bacteria.
Assimilation
Nitrification
Fixation
Denitrification
Process when the plants absorb nitrates from the soil into their roots.
Denitrification
Nitrification
Assimilation
Fixation
Process when extra nitrogen in the soil is put back out into the air.
Fixation
Nitrification
Denitrification
Assimilation
Ammonification is part of the decaying process. When a plant or animal dies, decomposers like fungi and ________turn the nitrogen back in ammonium so it can reenter the nitrogen cycle.
Animal
Oxygen
Bacteria
Rock
Denitrification is performed by
Oxygen
Rock
Animal
Bacteria
How do herbivoresobtain (get) the nitrogen they need?
They release nitrogen through decomposition when they die.
They absorb it directly from the air.
They consume animals that produce nitrogen compounds.
They consume plants that produce nitrogen compounds.
Match the steps of the nitrogen cycle to their definition
Nitrogen gas
The process of plants and animals taken in nitrogen
Nitrification
The process of converting nitrogen gas into a usable form, by either bacteria or lightning
Ammonification
Process where a type of bacteria, changes the useable nitrogen in the soil, back to nitrogen gas
Nitrogen fixation
Bacteria converting nitrogen compounds into NH3 (ammonia) or NH4+ (ammonium)
Denitrification
makes up about 78% of Earth's atmosphere by volume
Assimilation
Bacteria converting ammonia (NH3) to nitrates (NO3) and nitrites (NO2)
