2 Background on Nitrogen All life requires nitrogen compounds (e.g. DNA, proteins, etc.).Air, which is 79% nitrogen gas (N2), is the major reservoir of nitrogen.But most organisms can’t use nitrogen in this form.Plants get nitrogen by fixing it into a compound such as ammonia (NH3), urea (NH2)2CO, and nitrate ions (NO3−)Animals get nitrogen (compounds) by eating plants, or by eating animals that have fed on plants.
4 The Nitrogen Cycle There are 3 main ways that nitrogen gets recycled: Nitrogen FixationDenitrificationDecomposers
5 1. Nitrogen FixationNitrogen Fixation means taking atmospheric nitrogen (N2) and making it into a compound (e.g. NH3), which makes it useable for living organisms.Two ways:Energy from lightning:Lightning breaks N2, allowing N atoms to combine with oxygen forming nitrogen oxidesNitrogen oxides dissolve in the rain forming nitrates which are carried to the earth
6 1. Nitrogen Fixation (Cont’d) (B) Nitrogen Fixing Bacteria:Usually found in soil on plant rootsThese special bacteria can convert N2 into compoundsThey give the plant nitrogen compounds, and in turn, the plant gives the bacteria sugarBoth the plant and the bacteria benefit in this symbiotic relationship
7 2. DenitrificationDefinition: making nitrates into nitrogen gas, thus replenishing the nitrogen gas in the atmosphereThis once again done by bacteria
8 3. DecomposersWhen living material dies, it gets decomposed (broken down) by bacteria (decomposers).The decomposers convert nitrogen compounds to simple chemicals like ammonia or nitrates.These nitrates can recycle again by acting as a nutrient for plants.
9 How Does This Affect US?We might not hear a lot about nitrogen, but it plays a big role in our lives.Example: the use of agricultural fertilizers to increase plant growth.Is fertilizer use good or bad?
10 How Does This Affect US? Good: we can grow more food. Bad: ecosystems are becoming nitrogen rich. This often decreases the quality of an ecosystem by draining the oxygen.Example: In an aquatic ecosystem that is very nitrogen rich (eutrophic), the water quality drops, and usually fish and plant life decrease.
11 HomeworkDraw a simple DIAGRAM of the Nitrogen Cycle, showing Nitrogen Fixation, Denitrification, and Decomposers.
14 HomeworkUsing your textbook to help you, draw me a SIMPLE figure of the water cycle (p 523)Include the following terms in your diagram: evaporation, precipitation, condensation, and surface runoff (be able to define)Although I won`t be specifically teaching the water cycle, it is testable material.