Earth Science: Ecology – Cycle of Matter
Material cycling, as recurring processes, enable a return of matter into food chains.
Thus, an ecosystem in terms of its turn over can be independent of an external supply of matter, except for the (required) energy supply, e.g., through solar radiation.
Important material cycles include the carbon, nitrogen, phosphorous, and hydrogen cycles.
Earth Science: Biology – Ecology – Carbon Cycle and Nitrogen Cycle
Carbon plays a particularly important role in ecosystems, as it participates in fundamental biological processes. Nitrogen is also an essential sub- stance as it is required for the synthesis of proteins and nucleic acids.
All organic compounds contain carbon. The carbon cycle is a complex series of processes through which all of the carbon atoms in existence rotate. The very same carbons in our bodies today have been used in countless other molecules since the beginning of time. The carbon cycle starts out when autotrophs (organisms that can use inorganic material for nutrients, such as green plants) pick up carbon from the air in the form of carbon dioxide.
During photosynthesis, this is reduced to carbohydrates (sugars), which can serve as food for plant eaters. Subsequently, carbon is oxidized back to CO2, through respiration and fermentation. It is then returned to the air, so that the cycle is closed and balanced out again normally.
In recent decades, however, the carbon dioxide content in the atmosphere has steadily risen, especially due to the increased use of fossil fuels and other anthropogenic (or human-made) interventions into the global ecosystem. This has raised concerns about excessive carbon dioxide levels.
The nitrogen cycle
Nitrogen is an essential substance for all organisms because it is required for the synthesis of proteins and nucleic acids. So that nitrogen is available in sufficient amounts, individual forms of nitrogen are constantly being provided by a type of cyclic replenishment.
When nitrogen compounds from the excretions of animals, animal cadavers, plant remnants, and so forth reach the soil, they will eventually be broken down (proteolysis). Nitrogen is then released in the form of ammonia (NH3). Subsequently, bacteria oxidize this ammonia (through a process called nitrification) into nitrate (NO3-).
This newly created substance is then absorbed by green plants and built into organic compounds (proteins and nucleic acids) in a process known as nitrogen assimilation. Plant proteins and nucleic acids are then utilized by plant-eating animals for the development of their own proteins, because they cannot absorb inorganic nitrogen.
When plants and animals die, these nitrogen compounds are returned to the soil and the nitrogen cycle begins all over again.
BASICS
DENITRIFICATION The opposite process of nitrogen fixation is demtrification. where bacteria take in nitrate (nitrate respiration).
This releases elementary nitrogen