Objectives: S.W.B.A.T Describe the Nitrogen Cycle. Discuss how communities in an ecosystem are

involved in the Nitrogen Cycle. Explain the importance of the Nitrogen Cycle in

the environment.

DO NOW: DO NOW: Think about the following questions:Think about the following questions:1)1)Which macromolecule contains Nitrogen Which macromolecule contains Nitrogen as one of its elements?as one of its elements?2)2)What is the basic unit of proteins?What is the basic unit of proteins?3)3)How does the body get-rid off the excess How does the body get-rid off the excess nitrogenous wastes?nitrogenous wastes?These questions look very difficult and These questions look very difficult and complicated. Lets start at the beginning.complicated. Lets start at the beginning.

Nitrogen gas (N2) makes up 79% of our atmosphere

Nitrogen is needed by plants and animals to make proteins and DNA It ranks fourth behind oxygen, carbon, and hydrogen

as the most common chemical element in living tissues.

Most organisms CAN NOT obtain nitrogen through the atmosphere!

If nitrogen is so important, then how do we get it?

The Nitrogen Cycle

Most organisms can only use nitrogen in the form of nitrate (NO3-).

Most of the conversion of N2 to these compounds takes place under ground through bacteria.

This is called: Nitrogen Fixation.

Nitrogen Fixation:Bacteria convert gaseous nitrogen to ammonia:

(N2) (NH3)Some ammonia enters the ground normally through

waste and decay as well (pee, poop and dead things).Different bacteria convert ammonia to nitrite:

(NH3) (NO2-)

Bacteria use nitrite as an energy source,and give off nitrate (NO3-) as waste:

Nitrate is then taken up by plants orreleased into the atmosphere, where itbecomes gaseous N2 again.

(NO3-)

(N2)

Some plants (legumes) have nodules on their roots where nitrogen-fixing bacteria live.

Credits: • Images:

http://earth.rice.edu/MTPE/bio/biosphere/topics/energy/nitrogen_cycle.gif http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/earth_system/nitrogen_cycle_EPA.jpg http://www.paintthelight.net/BotanyProject/Activities/uses_plants.htm http://runforlife3.wordpress.com/2009/04/15/peanut-peanut-butter-and-jelly/

• Links: http://www.youtube.com/watch#!v=R8-E6cDCr5U