Toby Sandblom, Andrew Ward, and Rachel Clarkson Nitrogen Cycle

About Nitrogen ●Necessary for all living things ●Essential component for DNA, RNA, and proteins (the building blocks of life) ●Takes up 78% of the atmosphere as N 2 ●Major component of chlorophyll and is essential for photosynthesis

● The Nitrogen Cycle is a process by which nitrogen is converted between its various forms. ● Key Processes: o Nitrogen Fixation o Nitrification o Assimilation o Ammonification o Denitrification ● Affects rate of primary production and decomposition ● Nitrogen transformation is controlled by microorganisms, particularly bacteria ● Occurs within atmosphere, lithosphere, hydrosphere, and biosphere The Nitrogen Cycle

Diagram

Nitrogen Fixation ● Occurs in Lithosphere ● Conversion of gaseous nitrogen to ammonia NH 3 ● Combustion, lightning discharges, industrial processes etc.-> supply enough energy to break apart atmospheric nitrogen (fix considerable nitrogen) ● Nitrogen-fixing bacteria (ex: cyanobacteria) carry out biological nitrogen fixation in soil & aquatic environments o makes use of enzyme nitrogenase to split atmospheric nitrogen & combine resulting nitrogen atoms with hydrogen

● Symbiotic Nitrogen Fixation o Many microorganisms fix nitrogen symbiotically by partnering with a host plant. ● Nitrogen Fixation by Heterotrophs o bacteria live in the soil and fix significant levels of nitrogen without the direct interaction with other organisms. Nitrogen Fixation (continued)

● The conversion of ammonia or ammonium to nitrate ● Performed by soil bacteria in a two step process o First, ammonia or ammonium is converted to nitrite o Then, nitrite oxidizes into nitrate ●Bacteria gains energy through nitrification ●Fastest phase of cycle ●Occurs in lithosphere Nitrification

● Plant roots absorb nitrate, ammonia, or ammonium, and incorporate their nitrogen into plant proteins and nucleic acids ● When animals consume plant tissues, they assimilate nitrogen by taking in plant nitrogen compounds (amino acids) and converting them to animal compounds (proteins) ● Slowest phase of the cycle Assimilation

Ammonification ●Conversion of biological nitrogen compounds into ammonia (NH 3 ) and ammonium ions (NH 4 + ) ●Process ○ Organisms produce nitrogen-containing waste products (urea and uric acid) ■ Contained in urine and wastes of birds ○ Those substances are decomposed ■ Nitrogen is released into the abiotic environment in the form of ammonia ●Ammonifying bacteria facilitate this process ●Ammonia → nitrogen cycle → nitrification and assimilation

●Reduction of nitrate (NO 3 -) to gaseous nitrogen (N 2 ) ●Denitrifying bacteria-> reverse action of nitrogen- fixing & nitrifying bacteria by returning N 2 into atmosphere ○ live & grow where there is little to no free oxygen (ex: deep soil near water table) ●Occurs in lithosphere Denitrification

●Burning fossil fuels, the application of nitrogen-based fertilizers, and other activities can dramatically increase the amount of biologically available nitrogen in an ecosystem ●Where in cycle can humans affect it? ○Nitrogen av ailability can limit the primary productivity of many ecosystems. ○Industrial nitrogen fixation has increased exponentially since the 1940s, and human activity has doubled the amount of global nitrogen fixation ●How can humans decrease effect? ○ Decrease burning of fossil fuels Human Effect on the Nitrogen Cycle

Nitrogen Cycle’s Use for Humans ●Amino acids all contain nitrogen ○ make up the proteins in hair, muscles, skin, & other important issues ●Normal growth, cell replacement, & tissue repair all require nitrogen for production of new cells