Biogeochemical Cycles

Introduction Put biology, geology, and chemistry together, and you get biogeochemical. Organisms that live and then die are the bio part The earth that they decompose into comprises the geo part And the process by which organic matter returns to the elements is explained by the chemical part.

The Hydrologic (Water) Cycle Plants absorb water from soil, and animals drink water or eat animals, which are made mostly of water. When plants go through the process of transpiration (that’s when water evaporates from a leaf and more water is pulled up from the roots of the plant and out through the cells on the surface of the leaf), they give off water.

When animals create perspiration, they release water, which is evaporated into the atmosphere. Water is also released from plants and animals as they decompose. Decomposing tissue becomes dehydrated, which is what causes the dried-out tissues to break down and fall into the soil.

As water evaporates into the air, it cools and condenses, forming clouds. In addition, wind moves air over bodies of water. Clouds get heavy and precipitation (rain, snow, sleet, hail) eventually releases water into larger bodies of water such as lakes, rivers, oceans. A great deal of water is locked up in glaciers. Water from precipitation and decomposing tissue also gets into groundwater, which ultimately supplies larger bodies of water.

The Carbon Cycle Plants take in carbon dioxide for photosynthesis. Animals consume plants or other animals, and all living things contain carbon. Carbon is what makes these molecules organic (living). Carbon is necessary for cells to build molecules such as carbohydrates/carbs, fats/lipids, proteins. Animals release carbon dioxide when the respire (breath)

Plants and animals both release carbon dioxide when they decompose Plants and animals both release carbon dioxide when they decompose. Decomposing animals and plants leach carbon into the ground, forming fossil fuels such as coal or oil. Carbon dioxide is also released when organic matter such as wood, leaves, coal, or oil are burned. The carbon dioxide returns to the atmosphere. Some carbon is stored in the form of cellulose in trees and bushes.

The Phosphorus Cycle ATP, that critical energy molecule created by every living thing, needs phosphorus. You can tell by it’s name (Adenosine triphosphate) indicates that it contains three molecules of phosphate, which requires phosphorus. DNA and RNA, the genetic molecules present in every living things, have phosphate bonds holding them together, so they require phosphorus too, as does bone tissue.

Plants absorb inorganic phosphate from the soil. When animals consume plants or other animals, they acquire the phosphorus that was present in their meal. Phosphorus is excreted through the waste products created by animals, and it is released by decomposing plants and animals. When phosphorus gets returned to the soil, it can be absorbed again by plants, or it becomes part of the sediment layers that eventually form rocks. As rocks erode, phosphorus is returned to water and soil.

The Nitrogen Cycle Because amino acids build proteins, nitrogen is critically important. Nitrogen is present in the nucleic acids DNA and RNA. Life could not go on without nitrogen. The nitrogen cycle is the most complex biogeochemical cycle because nitrogen can exist in several different forms. Nitrogen fixation, nitrification, ammonification, and denitrification are all parts of the nitrogen cycle. Add nitrogen - nitrogen fixation and nitrification Remove nitrogen - ammonification and denitrification