What Is the Nitrogen Cycle?

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The nitrogen cycle refers to the way that nitrogen moves through the environment, a process that begins in the atmosphere and moves as nitrogen is changed into a usable form. Learn about the process of fixation with help from a science teacher and field biologist in this free video on biology.

Part of the Video Series: Biology & Organic Chemistry
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Video Transcript

Hi, I'm Brian with ericksontutoring.blogspot.com. Today we're going to discuss the nitrogen cycle. Nitrogen is a important and essential nutrient for, for life. But unfortunately, it's most abundant form is inaccessible for the organism, most of the organisms that need it. So this is a cycle, but we're going to start in the sky. Atmospheric nitrogen makes up approximately seventy nine percent of the atmosphere, but nitrogen as a gas is only usable by a few different organisms. So, nitrogen needs to be changed into usable form. This process is called fixation. Basically, bacteria that are associated with legumes, soak peas and other plants of that variety as well as bacteria that are living freely on the soil and are associated with other plants like alders which are type of tree; they fix nitrogen which simply means they change it from, from gas, from a gas into, into ammonium which is NH4 . From this stop, ammonium can be used by plants but it also goes through another process called nitrification which essentially means that ammonium is changed by bacteria again into nitrites and then into nitrates. The reason it can't stop at nitrites is that nitrites when they build up in the soil become toxic for plants. So they have to go all the way into usable form nitrate. So now we're ready for plants to take up these nitrates and ammonium; this process is called assimilation and basically plants assimilate nitrogen into usable form into their roots. They build cell structures; they incorporated in the chlorophyll and also through different things. So, but now your consumers; so all animals and, have to get nitrogen as well; but in order to get it they have to eat the plants. The next step, when the consumers die or when they excrete, decomposers break down the organic molecules and turn them back into ammonium through a process called ammonification, making ammonium. And the last, that essentially serves as the recycling process. The last major step, another type of bacteria turns nitrates and through denitrification which essentially means denitrifying; sorry, that wasn't very, that didn't clarify things much. But they turn nitrogen back into a gas and it reenters the atmosphere and closes the cycle. This has been a brief discussion of the nitrogen cycle and the way that nitrogen moves through the environment.

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