because the Earth is finite matter has to be reused and recycled over and over again so the atoms that are in you or once in the air in soil in water and in rocks these atoms have also been used by countless other living things from dinosaurs to broccoli plants to Abraham Lincoln and after they leave you they will become part of other living things or of the environment this recycling of matter is known as a nutrient cycle and there are several different nutrient cycles for different elements today we will focus on the nitrogen cycle the
process by which the element nitrogen moves around in ecosystems the nitrogen cycle is crucial for all life on Earth because nitrogen is needed to make some of the most important molecules for life including DNA RNA and proteins that are needed by all living things without nitrogen there would be literally no Life as We Know It so it's important to understand at least a little bit about how the nitrogen cycle works right so let's get into it nitrogen gas N2 makes it about 78 percent of our atmosphere you breathe it in and out all the time
in fact you're doing it right now the problem with N2 is that you can't use it to make any of the cool molecules we just discussed the three bonds between the nitrogen atoms and N2 make it very hard to break apart so you can't do any reactions to make DNA or RNA or proteins or anything else the nitrogen atoms are essentially super glued together luckily there are certain bacteria that can break the triple bond of nitrogen gas to make something that organisms can use these bacteria are called nitrogen fixing bacteria and they are found in
the soil and in root nodules of certain plants known as legumes as well as a few other places these nitrogen fixing bacteria break nitrogen gas apart and add hydrogen atoms to it to form ammonia NH3 or ammonium nh4 plus we can fix it yes we can you put another h on there it's ammonia it's basically the same it's just ionized this process moves nitrogen from the air to the soil and is called nitrogen fixation because the nitrogen in the air is getting fixed so other living things can use it ammonia can be taken up by
plants and used to make important biological molecules like DNA and proteins Etc this process of uptake and production of biological molecules is called assimilation but not all of the ammonia produced by nitrogen fixation gets assimilated into plants too much ammonia can be toxic and sometimes plants prefer to assimilate other nitrogen compounds called nitrates our next step is the conversion of ammonia into nitrates a process called nitrification hey we already fixed it concerning plants prefer nitrates nitrification is done by nitrifying bacteria these bacteria oxidize or add oxygen to ammonia in chemical reactions that first convert the
ammonia to nitrite NO2 minus and then to nitrate NO3 minus because oxygen is needed for these reactions nitrification happens best in soils that are well aerated like ammonia nitrate is a plant fertilizer because it can be assimilated and used to make key biomolecules DNA RNA proteins Etc once nitrogen is inside of plants and used to build our sweet biomolecules it can pass to other living things through food webs when an animal eats the plant the nitrogen containing compounds in the plants move to the animal when that animal gets eaten nitrogen moves to its predator and
so on eventually all living things die and decompose this Returns the nitrogen back to the soil as ammonia in a process called ammonification this ammonia can now be used Again by plants or converted to nitrates by nitrification and so nitrogen gets cycled around and around over and over again but we are still missing one key part of our cycle in order to have a complete cycle nitrogen gas needs to get back into the air this is done by denitrifying bacteria and is called denitrification during denitrification bacteria convert nitrates NO3 minus into nitrogen gas N2 denitrification
happens best in low oxygen environments like waterlogged soils and it reduces the fertility of the soil this is one reason why it's harmful to over water plants so now we've completed the entire nitrogen cycle since we're back at our starting point of nitrogen gas in the atmosphere let's do a quick review first nitrogen fixation fixes nitrogen gas to make ammonia this ammonia can be assimilated into plants or go through nitrification to make nitrates nitrates can also be assimilated by plants or undergo denitrification and be converted back into nitrogen gas also nitrogen moves through food webs
and is transferred whenever one organism eats another when these organisms die they get decomposed and their nitrogen becomes ammonia again via a monification and there you have it the nitrogen cycle now to review and practice the nitrogen cycle play the interactive game for free on the bioman biology website biomanbio.com if you enjoyed this video feel free to like And subscribe thanks
