Biogeochemical Cycles

A) Carbon is how biologists determine if something is organic or not, as all organic organisms contain carbon. It is one of the few universally common things about life. Carbon helps and hurts with many things. It reacts with almost every other element. This is because it only has 4 valence electrons, which means it covalently bonds with other elements very easily(1).

http://www.ccs.k12.in.us/chsBS/kons/kons/images/carbon.gif

Carbon can take on many forms due to this as well. It can be the three forms of elements (solid, liquid, gas) all at the same temperature. As a solid, we carbon in places such as limestone, graphite, lead, and even diamonds. As a liquid, carbon can be in our drinks, in the form of carbonic acid. As a gas, carbon can be in many forms, such as carbon dioxide and carbon monoxide. Carbon can move through all these stages fairly quickly. A fairly good example of a carbon cycle would be a limestone rock being eroded by water, where carbon is released into the atmosphere as CO2. This CO2, if in high enough concentrations, can join into clouds and rain down as a form of acid rain. A fair amount of times, this rain lands in a body of water, which is then consumed by organisms. These organisms eventually die and their carcass slowly forms into a carbon deposit in the earth. Over hundreds of years, this turns into stone, bringing the cycle back to its origin. Society is benefited by carbon in many ways. Many structures would not have been build without carbon, as most compounds include carbon. Diamonds, lead vests, pencils, and many other items we know today would not exist if not for carbon. However, carbon also is a large contributer to global warming, as it creates holes in the ozone layer and also holds onto heat in the atmosphere.

http://www.met.utah.edu/jhorel/companion/gifs/carbon_cycle.gif

B) The nitrogen cycle is a very large part of Earth's life systems. Nitrogen is included in the four most common elements on Earth, along with oxygen, carbon, and hydrogen(2). The cycle moves much-needed nitrogen into different parts of ecosystems in different forms. Many organisms use nitrogen to sustain themselves. Nitrogen is cycled through by all kinds of plants, animals, and fungi. Each one doing something such as nitrifying bacteria or other matter in each step of the cycle.

http://fig.cox.miami.edu/faculty/dana/nitrogencycle.gif

C) All elements in nature can be dangerous to living organisms. This works great with the idea of having things in moderation. Even water, something that we are always told we never get enough of, is dangerous in large quantities. A lot of this has to do with the pH of substances. Small amounts of an acid aren't too harmful, such as tomato juice. However, if you were to eat enough tomatoes, you would probably start to get acid reflux, which is your body telling you when you've had enough. Many different elements can be used as an example. Medicines are a prime example. We take things such as aspirin to help ourselves, but having too much aspirin has been linked to deterioration of the intestinal lining.

Bibliography

(1,2)Campbell, N. A. (Ed.). (2008). Biology eighth edition. San Francisco, CA: Pearson Benjamin Cummings.