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The importance of nitrogen cycle
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The Significance of the Nitrogen Cycle in Ecosystems
Nitrogen makes up about 80 per cent of the Earth's atmosphere as a
gas. However the gaseous molecule is very stable and has to be
transformed before it can be used by most organisms as it is only
available to them when it is ammonium or nitrate. It can only be
removed from the atmosphere in two ways: by lightning and by nitrogen
fixation. Only a few species can convert nitrogen by nitrogen fixation
to biologically useful forms. Due to this, biologically useful
nitrogen is often in short supply and can be the limiting factor in an
ecosystem.
There are five main steps in the Nitrogen cycle:
Biological Nitrogen Fixation
This is the conversion of gaseous nitrogen to ammonia using an enzyme
called nitrogenase that only works in the absence of oxygen and
requires large amounts of energy. The equation for nitrogen fixation
is:
N + 8e + 8H + 16ATP ® 2NH + H 16ADP + 16Pi
Often the nitrogen fixers live in close association with a specific
eukaryotic organism. Although their biomass is small their role in the
biosphere is just as important as that of the photosynthetic
autotrophs fixing ninety million tons of gaseous nitrogen per year
(Jones, 1997). Various photosynthetic bacteria, including
Cyanobacteria are the main nitrogen fixers. On land most nitrogen
fixation comes from the bacteria associated with the formation of root
nodules in certain plants with free-living soil bacteria making only a
small contribution.
Some bacteria belonging to the genus Rhizobium live in close
association with the roots of leguminous seed plants such as peas,
soybeans and alfalfa. The...
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8th Septmber 2003
http://scholar.hw.ac.uk/heriotwatt/scholar2003/courses/advanced/Biology/unit2/activity18.asp?outline=no
Jones, A (1997) "Environmental Biology", Routledge, USA and Canada
p81- 84
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Nebel, Bernard J., and Richard T. Wright. Environmental Science. 6th ed. Upper Saddle River, NJ: Prentice Hall, 1998.
Tibbetts, John. "Environmental Health Perspectives." January 2006. Louisiana-A lesson in Nature Appreciation Vol. 114, Number 1. 4 December 2010 .
One of the main questions addressed is; why do plants choose rhizobia with nitrogen fixing strains (as nitrogen is metabolically costly) over plants with non-fixing strains that can also lead to nodulated plant (Gubry-Rangin et al, 2010). It should be noted that strains with different fixing levels have been reported in populations of rhizobia and when picking a rhizobium a plant must take into consideration its symbiotic efficacy, as rhizobia cannot be vertically transmitted.
The leguminosae family, more commonly known as the legume, pea, or bean family; contain most of the plant species that form a symbiotic relationship with nitrogen fixing bacteria. About 20,000 species of legumes form their symbiosis with rhizobia; a nodule-inducing bacteria. Legumes have emerged as a very valuable resource for many countries for various reasons. The seeds of legumes are very high in protein, and some can also be rich in oil. Some countries donate up to 60% of their arable land in order to plant various types of this plant family. This family of plants is also used to enhance soil fertility and is a valuable source of wood. In various agricultural systems, the need for chemical fertilizer is greatly reduced due to the nitrogen fixation of the symbiotic bacteria that is hosted by the legumes. In some areas, almost 50% of the nitrogen added to the soil is due to this symbiotic relationship (3). Although an exact estimate of this symbiosis is hard to determine, legume-rhizobia relationships remain important to the function and composition of many natural ecosystems throughout the world (2).
Audesirk, Teresa, Gerald Audesirk, and Bruce E. Byers. Biology: Life on Earth with Physiology. Upper Saddle River, NJ: Pearson Education, 2011. 268-69. Print.
The ecosystem I have chosen is tropical rainforest. In the following paragraphs, I am going to firstly introduced the structure of tropical rainforest in brief, with the second part of the plant ecology and last the diversity within this ecosystem.
middle of paper ... ... World Book Inc, 2000. Davis, Lloyd S. and John T Darby. Penguin Biology. San Diego: Academic Press, Inc., 1990.
Raven, Peter H., Linda R. Berg, and David M. Hassenzahl. "Wiley: Environment, 6th Edition." Wiley: Home. Web. 05 Feb. 2012. .
I believe that Lions are very important for its ecosystem. Lions account for around 85 percent of the predation on the Serengeti’s. Lions have special importance as the only predators on the savanna capable of killing Africa’s largest herbivores, such as elephants and giraffes. Lions prey primarily on herd animals, the attack the weakest animal, since most animals protect their young so they are mostly either old or sick. Since they mostly kill the ones that are either old or sick they lower the other animals of getting diseases so they keep the population balance between the animals.
Gazzale, L (2007), retrieved January 22, 2007 from University of Phoenix, Main MBA501 week five environmental scanning thread
Microbial decomposition releases nutrients into the environment that are needed by other organisms. Microbes are also involved in the cycling of many other important compounds in — and between — ecosystems, including oxygen, carbon and nitrogen. Many microbes use the energy of sunlight to convert carbon dioxide to oxygen, which we need to breathe. As they do this, they create new organic material — themselves — which are then eaten by other organisms. In this way, the cycling of nutrients and energy
The discovery of widespread trophic cascades has been one of the most exciting scientific findings for the past half century. A trophic cascade is an ecological process which starts at the top of the food chain and tumbles all the way down to the bottom. An example of this is the Yellowstone national park in the United States when wolves were reintroduced in 1995.
People have been relying for their daily needs and well-being on nature. The natural ecosystem provides varieties of goods and services to us, for instance, fresh water, fisheries, timber, water purification etc. The benefits that people directly get from the natural systems are called ecosystem services (ES).
Studies have shown that there are bacteria and fungi with certain strains that live in soil. When they are applied to the seeds, they can aid crops by invigorating plant growth or by decreasing the damage created from plant pathogens bred from the soil. Another example is the bacterial species, Mycorrhiza. It is a fungus, which is able to form a union with a majority of land plants. When this action occurs, that symbiotic relationship assists to increase uptake by the root system to about 90 percent. This in turn helps the plant take in water and nutrients from deep inside the soil. It also allows the activation of genes and physiological changes in the plant which helps them to survive drought circumstances. Other microbes are also able to lift a plant 's resistance to bugs. A larger focus on microorganisms colonizing our plants and sharing a symbiotic relationship with them would greatly improve yields and lessen the need for costly fertilizers and pesticides. Information such as this would be very useful for students in college who are interested in businesses such as