The myriad variety of life is classified in a number of ways, dependent on scientific questions and need. Scientists utilize taxonomy to name and classify organisms, and they use systematics to create phylogenies—the evolutionary history of a species or group of species. Perhaps the most commonly known classification scheme utilizes evolutionary relatedness and a hierarchy of increasingly exclusive categories: domain, kingdom, phylum, class, order, family, genus, and species.
The following hyperlink provides a nice classroom Powerpoint slide show: Naming and Classifying Organisms [6].
Links
[1] https://www.tuhsd.org/
[2] http://en.wikibooks.org/wiki/General_Biology/Classification_of_Living_Things/Classification_and_Domains_of_Life
[3] http://www.diffen.com/difference/Autotroph_vs_Heterotroph
[4] http://en.wikipedia.org/wiki/Trophic_level
[5] http://soilweb200.landfood.ubc.ca/soil-biology/soil-organisms/
[6] http://krupp.wcc.hawaii.edu/BIOL200/powerpnt/pdffiles/classification.pdf