02.04 Biogeochemical cycles

Join NURSING.com to watch the full lesson now.

Included In This Lesson



  1. Biogeochemical Cycles- How matter that is necessary for living organisms cycles from life to the lithosphere, atmosphere and hydrosphere.
    1. Role of Microbes- Microbes assist in the breakdown of many macromolecules into their monomers to allow for recombination and recycling.
    2. Carbon Cycle- involves CO2 released in atmosphere through combustion of fossil fuels, microbes release CO2 through decomposition r both in atmosphere and in soil, respiration by living things releases CO2 into oceans, atmosphere and soil, ocean uptake of CO2 through wind and rain, deforestation and land use increase CO2 in atmosphere. Photosynthetic organisms like plants and certain microbes remove CO2 from atmosphere and fix it.
    3. Nitrogen Cycle-Lighning and nitrogen fixing bacteria in soil convert atmospheric nitrogen (N2) into ammonia (NH3) and Ammonium (NH4) which can naturally go through nitrification and convert into nitrites (NO2) which can be assimilated by plants. Decomposers break down organic matter (dead plants, animals and urine) and make NH3 and NH4 through ammonification.Emissions from burning fossil fuels can put N2 back into the atmosphere.
    4. Oxygen Cycle- oxygen cycling from life to the land, water and atmosphere. Oxygen is produced from life through photosynthesis and given off into the atmosphere and hydrosphere.Oxygen is consumed primarily through cellular respiration and decompostion (thanks to bacteria).


Today we’re going to be talking about biogeochemical cycles.

The term biogeochemical can be chunked and analyzed to understand and remember what it means. Bio means life, geo means Earth and the chemicals involved that cycle between the two main reservoirs. More specifically we can consider how these chemicals from life to the Earth’s land (lithosphere, air (atmosphere) and oceans (hydrosphere).

One foundational chemical of life is carbon which is a major player in this cycle. This process involves carbon dioxide being free into the air, soil, and water through combustion, respiration, and decomposition. Photosynthesis is the process that then can fix carbon dioxide from the atmosphere and lithosphere allowing it to be then converted in forms that eventually take part in respiration, decomposition, and combustion that once again frees carbon dioxide as the cycle continues.

Another key chemical used in the production of protein and nucleic acids in living things is nitrogen. Of course, this fixation of nitrogen could never occur if not for bacteria and lightning freeing diatomic nitrogen allowing for it to recombine with hydrogen and turn into ammonia, ammonium and then nitrification to eventually be assimilated by plants only to be broken down and released back into the soil and atmosphere through decomposition and ammonification.

And the last cycle we are going to look at is the oxygen cycle. Oxygen is freed through photosynthesis decomposition and then fixed through cellular respiration. Additionally, sunlight and weathering can also free oxygen and allow it to escape into the atmosphere or become dissolved in the water or soil through wind, waves, erosion and rain.

So to summarize, biogeochemical cycles allow for chemicals to cycle through life,  land, sea and air. Specifically, these chemicals important to life are carbon, nitrogen and oxygen which share similar processes that either fix or free them as they cycle.

We love you guys! Go out and be your best self today! And as always, Happy Nursing!