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The Nitrogen cycle (p.52-65) Why nitrogen? All living things need nitrogen to live Nitrogen is an essential component of proteins and DNA Nitrogen Fixation Plants (p.54-55) need nitrogen, phosphorus and potassium that we can find in fertilizers. So it’s convenient that 80% of our atmosphere in nitrogen gas! BUT… plants aren’t capable of absorbing nitrogen directly from the atmosphere. They need some help Solution… In soil and water there are Nitrogen fixing bacteria. Many of these live on the roots of beans, peas, clover and similar plants How? Nitrogen is combined with hydrogen and oxygen to form ammonia or nitrates (NH4+) (NO3-). Before artificial fertilizers, farmers planted peas, beans and clover to make the earth fertile again. The Nitrogen Cycle in a Terrestrial ecosystem 1) Nitrogen is converted to ammonia by Nitrogen fixing bacteria and to nitrates by nitrifying bacteria. 2. a) Plants absorb the nitrate so it can enter the food chain 2. b) OR the nitrate is transformed into nitrogen gas by denitrifying bacteria. This way, the nitrogen gets back into the atmosphere. If there’s too much nirtogen in the soil It degrades tree roots Needles yellow and fall. When they decompose they make the soil more acidic. Acidic soil can dissolve toxic metals like aluminum Aluminum kills fungi that live on roots and help trees absorb minerals. In the atmosphere Burning fossil fuels releases nitrogen compounds into the atmosphere This causes acid rain Eutrophication Nitrogen fertilizer runs off from farms, gardens and lawns into the water Causes Which accelerated plant growth uses all the oxygen and other elements needed by the fish In the oceans: Algal blooms Creates huge mats of (sometimes toxic) algae that can be seen from space. Things you need to remember 1- Plants and animals need nitrogen 2- They can’t use the nitrogen in the atmosphere directly 3- We rely on nitrogen fixing, nitrifying and denitrifying bacteria to convert back and forth between the type we can use (nitrate) and the type we can’t (nitrogen gas) It also helps to know… 4- These bacteria also convert the nitrogen in excrement and decomposing things 5- Too much nitrogen in the wrong place can cause: -soil to become acidic -acid rain -eutrophication (lakes choked by weeds) -algal blooms in the ocean