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This study seeks to identify the various animals that are found in the soil; they vary in size and numbers. An electron microscope that gives a clear analysis of the soil components is used to view the samples of the soil. The study helps the reader to understand the millions of microorganisms living in the soil; some of the microorganisms living in the soil are too small they can only be viewed under the microscope. Johnson 1979 states that these animals eat organic matters such as grass clippings, fallen plants, and algae. They reduce dead organic matter on earth’s surface and release nutrients from the decomposing organic matter for living plants to use.
The soil animals form the most crucial composition of the soil; they add organic matter into the soil and add the soil fertility of the soil. Various methods will be used to collect the samples of the soil that will be analyzed from different environmental conditions. A discussion of the results from the various methods used is done; a conclusion is the drawn from the results.
Soil animals are the micro organisms that are found in the soil; they form a highly crucial composition of the soil. They are responsible for the soil aeration as well as its fertility; they also influence soil color and its nutrient levels. They increase the organic content of the soil and control population of pathogens; they improve and maintain soil structure, and mix the organic matter with the soil. The soil animals aids in formation of a good soil structure by formation of pores and channels that holding fine soil particles together; and mix the organic matter through the soil. This leads to formation of a well balanced soil in terms of nutrients, moisture and aeration; which are vital for plants and other purposes that soil serves. Killham, 1994 states that soil has a large composition of soil microbes that are responsible for soil matter formation and decomposition; the ecology of the soil is manipulated by small microbes that can only be viewed under a microscope.
To examine the soil animals and analyze them; a microscope is used because of the small size of the animals that are in the soil. An electron microscope is used to examine the soil in this case. Macmullan, 1993 explains that Electron Microscopes function exactly like other microscope but the microscope uses a focused beam of electrons instead of light to image; and gain information as to its structure and composition. A stream of electrons is formed and accelerated towards the specimen using a positive electrical potential. The stream is confined and focused using metal apertures and magnetic lenses into a thin, focused, monochromatic beam. The beam focuses on the sample using magnetic lens; then interactions occur inside the irradiated sample, affecting the electron beam.
Soil animals are classified into 3 groups; this depends on their size.
They are the smallest soil animals and they range from 20-200 um; an example of a soil animal in this group is the protozoa.
This is the second largest group of soil animals and it ranges from 200um to 10mm; it is made up of collembolan, mites, and nematodes.
This is the largest group of soil animals that is in existence today; it is made up of beetles, termites and earthworms. The wonder science magazine states that earthworms are like earth tillers, they decompose the dead matter and excrete nutrient rich casts into the soil; they also help in water infiltration, and aeration.
Scientists and other people studying soil and its composition have the option of using the light microscope or the electronic microscope; but in this case the student will use the electron microscope.
Methods used to study soil animals using the Electron microscope
Just like the light microscope, an electron microscope too can be used to examine the soil animals as well as analyze other microorganisms that are present in the soil. However, the electron microscope gives a more detailed view of the soil components; this enables the researcher to get clear results that are easy to analyze.
Direct culture methods
The soil should be taken intact and placed on a nutrient medium then it is incubated; this results into small colonies that can be examined under the electron microscope. The different types of microorganisms present are cultured and identified. Another method used is the scotch tape that can be used to take samples of exposed soil samples; the samples are then incubated under the agar medium. The position that the colonies are in on the plates, reveals the distribution and location of the different microorganisms in the soil. The soil is then examined under the electron microscope.
Fluorescent antibody and related methods
This method is used to locate the small microorganisms that are present and intact in the soil; the microbial cells that are being studied are ejected into a suitable animal. After incubation the animals produce anti bodies into the injected microbial cells that can be isolated from the serum samples of the animals. After the excess FTIC-antibody has been removed by cleaning up the cells with fluoresce; the cells can now be examined under an electron microscope so as to identify them. This technique is mostly used to identify the nitrogen fixing Rhizobium spp, various fungal genera, Baccilus spp, and a few actinomycetes.
Enzyme-linked immunosorbant assays
This technique is mostly used in the Rhizobia in soils and roots of legumes; the method is used to find the specific microorganisms by identifying nucleic acids in the microorganisms under study.
These methods use various techniques to investigate and determine the distribution of microbial distribution in the soil; the Rossi- Choldny slides are simple to examine because the microscope slides are buried in the soil and left there fo some time before examination by use of an electron microscope. The examiners use strips of transparent chitin and cellulose materials; they also used small bore glass capillary tubes called pedoscopes.
Elective culture methods
Some chemical compounds are added into the soil in the field or in a laboratory; they are then incubated under specific conditions. The microorganisms are then left to grow under suitable conditions that enable them to multiply in numbers. This concept is the basis for the large number of industrial uses for soil microbiology, such as, fungi and bacteria to produce new antibiotics; the criteria can also be used when a person wants to separate specific microorganisms from others. Under such methods, we discover that soil from oil refineries contains more hydrocarbon degrading bacteria than the soil found in the farm fields. This method also shows the large soil organisms that are related to a certain physical or chemical environment; this is a reflection of the large degree of diversity in the soil that leads to many microbial niches.
Selective culture and media
All the media used in the laboratories to examine soil animals are selective in some way; therefore, there is no non selective media. The media and incubation conditions can be made by use of physical and chemical modifications; this leads to successful separation and counting of the various organisms in the soil under an electron microscope. This is done to remove a small sample of each colony and putting it in another fresh plate. The colony is then studies under a microscope to identify the various organisms that are in the soil
Discussion of results and observations
When an electron microscope is used to analyze soil; clear and concise results are observed. When the above methods are used to select the samples for analysis; the following observations are made when using the electron microscope.
According to Johnson 1979, the main composition of soil is organic matter that is from the soil animals and their various activities in the soil; soil is the main habitat of many soil animals.
Without the soil animals, there would be no decomposition in the soil; this is because they are responsible for the decomposition of the soil matter. The study shows that:
Fungi grow better on a medium with high Carbon: Nitrogen ratio
Bacteria grow better on a low C: N ratio media
Bacteria from soil grow better on weaker strength media; high nutrient levels can inhibit some soil isolates.
Many bacteria and fungi produce some antibiotic compounds that inhibit growth of other microorganisms in the soil.
Spores from common fungi such as Penicillium, Mucor, and Aspergillus in the soil grow rapidly on many fungal media and they prevent the development of other microorganisms that grow slowly.
There are different animals and plants living in or on the soil (including micro-organisms and humans); the amounts of nutrients, water, plants need affects the way the soil forms. Animals living in the soil affect the rate of decomposition of materials, and how soil materials are moved around in the soil profile. Although some of the soil animals are visible, it is however, very hard to see some soil animals with bare eyes because of their size; therefore, microscopes and other types of magnifying lenses are used to see these small animals.
Macmullan,1993 states that when using the Electron microscope, one gets elaborate results from the study; this because of the high levels of the magnifying capabilities of the lenses. In most cases, the most common soil animals that are found anywhere are the beetles, collembolan, earthworms, nematodes, and the mites. Some animals can be found in almost every environment on the surface of the earth; different species can grow and survive in majority of the conditions. The soil animals require sufficient nutrients, carbon, moisture, an optimum PH, oxygen, and temperature for them to survive. The optimum PH and temperatures requirements vary between species; some of the microorganisms do not survive in cold conditions while others cannot survive on hot conditions. When the soil animals are in unfavorable conditions, they leave eggs in the soil that hatch when the climatic conditions become favorable. Other soil animals remain inactive and become active again when the conditions become favorable.
Animals like earthworms live deep in the soil when there are unfavorable conditions near the soil surface. Killham, 1994 explains that a change in soil temperature can have a considerable change in the microorganism activities in the soil; a different weather condition limits the activities of the soil animals.