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Name _______________KEY________________ Period _______ Nitrogen Cycle Packet What is Nitrogen? Nitrogen is an element found in the organisms on our planet, the atmosphere, water and soil. Living things cannot exist without nitrogen- it is an essential nutrient that living things use to make proteins and DNA. Atoms of nitrogen move slowly between living things, dead things, the air, soil and water. These movements are called the nitrogen cycle. Reservoirs are the areas where nitrogen is stored, such as the atmosphere, living organisms, soils and bodies of water. Most of the nitrogen on Earth is found in the atmosphere. Almost 80% of the air we breathe is made up of nitrogen. In the air, nitrogen is found as N2, which is two nitrogen atoms bonded together by a very strong triple bond. Because this bond is so strong, it is difficult to break the N2 into forms that plants N2 and animals can use to make proteins and DNA. In order for living things to use atmospheric nitrogen (N2), it must be converted into a different form such as those found in the soil or water [nitrate (NO3-) or ammonium (NH4+)] or into organic nitrogen (found in organisms). Plants take in nitrogen from the water through their roots and animals take in nitrogen by eating other plants/animals which contain proteins made partially of nitrogen. Nitrogen cycles throughout these different forms all the time. 1. What is nitrogen used for in living things? _____PROTEINS AND DNA________ 2. List 4 reservoirs where nitrogen can be found on Earth. ATMOSPHERE, SOIL, GROUND WATER, OCEANS ________________________________________________________________________ 3. Where is the majority of Nitrogen found on Earth? ATMOSPHERE 4. In what form is atmosphere nitrogen? ATMOSPHERE= N2 IN GAS FORM 5. Why is it difficult to convert atmospheric nitrogen into a usable form? IT HAS A TRIPLE BOND BETWEEN NITROGEN ATOMS THAT IS VERY HARD TO BEAK BY PLANTS AND ANIMALS. 6. List 3 other forms that nitrogen is found in other than atmosphere nitrogen. NO2 -, NO3-, NH4+ and N2O 7. Where is organic nitrogen found? IN LIVING THINGS. 8. Write the letter that matches each term for the diagram below. A B O C N P D F L E G M K H J I _O_ Denitrification _E_Nitrogen Fixation _P_ Assimilation _K_Nitrification (2) _C_Organic Nitrogen _G_Mineralization _L_ Nitrates (NO3-) _M_ Leaching _N_Denitrifying bacteria _A_ Atmospheric N2 _F_ Decomposers _D_Nitrifying bacteria _B_ Lightning Fixation _J_ Nitrites (NO2-) _H_ Ammonium (NH4+) 9. Fill in the chart below: Compound Atmospheric N Nitrates Nitrites Formula N2 NO3- Compound Ammonium Formula NH4+ Nitrous Oxides N2O NO2- 10. Fill in the conversions below with the correct formulas (use the chart from #9 to help): Nitrogen fixation (ammonification) turns _____ N2______ into _____ NH4+____. Nitrification turns _____ NH4+______ into _____NO2-______ and finally into ____ NO3-_____. Assimilation turns _____ NO2-_____ or _____ NO3-________ into __ORGANIC NITROGEN_____. Mineralization turns into __ORGANIC NITROGEN____into ______ NH4+_______. Denitrification turns ___NO3-______ into ______N2________ or _______N2O_______. 11. Explain how humans are contributing to the Nitrogen cycle (do not just list them). • Fertilizers add synthetic N into water and soil • • Burning Fossil Fuels • • Can cause eutrophication Releases nitrous oxides into atmosphere, leading to acid rain Sewage & Livestock • Animal and human waste adds nitrogen to soil & water 12. List 4 ways that nitrogen gets into rivers or lakes, causing eutrophication. Runoff – Washes fertilizers/manure/urine into Acid rain: From either denitrifying bacteria or water burning fossil fuels releasing N2O into the air, eventually forming acid rain Animal waste :Urea is found in animal urine, Soil Leaching: Nitrates are leached from the soil which can be found in waterways or leached from into nearby waterways the soil into waterways Use the word bank to fill in the blanks below: Word Bank Denitrifying Assimilation Nitrifying Proteins Roots Mineralization Nitrates Ammonium Decomposes Leached Atmospheric N2 Organic N 13. Bacteria found in ____ Roots ____ of legumes, in the soil, or lightning can fix nitrogen from atmospheric nitrogen into __ Ammonium ___, a form that plants can use. 14. _____ Nitrifying _______ bacteria turn ammonium (NH4+) into _________ Nitrates ___________ (NO3-), which is the form of Nitrogen that plants prefer to absorb. This is also the form that is easily ________ Leached _______ from the soil. 15. During _____ Assimilation ______, plants absorb NO3- or NH4+ and turn the N into ____ Organic Nitrogen ________, eventually making ______ Proteins ______ or DNA. 16. During _____ Mineralization ______, organic N is converted into ammonium (NH4+) when an organism _____ Decomposes ______. 17. _________ Denitrifying __________ bacteria turns nitrates (NO3-) into _ Atmospheric N2 , completing the nitrogen cycle. Challenge Question: 18. How will an excess of nutrients from fertilizers in the rivers and lakes affect the food chain (particularly the animals that eat plants)? Excess nitrogen makes algae bloom killing many of the underwater plants. Algae is not a plant form that many animals eat so this will impact their food source. Furthermore, as eutrophication of the waterway continues the animals will die from a lack of D.O. in the water causing a shortage of food to other species that eat fish, amphibians or crustaceans. Eventually as the waterway dies all species will need to find a new source of food and the waterway will be dead and anoxic.