Learning Objectives for this lab:

Contents of this laboratory:

Introduction:

Today you will be learning about living organisms that exist on our planet. There are so many types of living organisms that it could be baffling to try to understand each and every one on its own. So, scientists have come up with a classification system to group similar organisms together. This system groups organisms by categories, based on their characteristics. The field of classifying organisms is called TAXONOMY.

    In taxonomic classification, all organisms are grouped into major categories, called DOMAINS.  Within the domains, another category called KINGDOMS can be used.  Even within a kingdom there is a lot of variety among the organisms; this requires that within each kingdom, the more similar organisms are grouped into smaller and smaller groupings, starting with PHYLA (or divisions).  As the characteristics for each organism are evaluated, eventually the groupings get so small that they only include quite similar organisms, for which the category is called a GENUS (plural:  genera).  Finally, each type of specific organism is given its own specific name to define it as different from every other organism, and that individual classification is a SPECIES.

    Since every kingdom is made up of many, many organisms, it should now be clear that each kingdom would have numerous phyla.  Likewise, each phylum would have numerous subcategories within it.  This continues so that eventually, the millions of species all fit nicely into the classification system.  For a more complete description of the taxonomic categories, and for some examples of how they are used, please see Appendix A at the back of this lab handout and Figures 8-6 and 8-8 in your book.

Domains and Kingdoms:

    All of life has been classified into three major domains:  Archaea, Bacteria, and Eukarya.  Both Domain Archaea and Domain Bacteria contain organisms composed of prokaryotic cells.  These domains are new classifications and are still being described by scientists.  In Principles of Biology I, we focus primarily on those organisms composed of eukaryotic cells in the Domain Eukarya.  Here is a table to help you understand the relationship between cell type and domain:

    Within domains are kingdoms.  In the prokaryotic domains, the kingdoms are being worked out—currently, your book assigns one kingdom per domain.  However, in the domain Eukarya, 4 kingdoms have been described.  We have added to our table of the domains to show which kingdoms belong in which domain:

    Of course, this classification system is only relevant to us if we have methods for distinguishing each of the kingdoms.  It would be tricky for us to try to distinguish among the prokaryotic domains, but fortunately, we will only be observing organisms that fit into Domain Bacteria today.  Therefore, throughout this lab, it will be your job to classify organisms as belonging to either the Domain Bacteria or one of the 4 eukaryotic kingdoms

Characteristics Useful for Classification:

    Now comes the really crucial part—distinguishing each kingdom from the others or from the Domain Bacteria.  The organisms within one classification group share more in common with each other than they do with other organisms.  Therefore, one can define common characteristics for each group, and use them to describe the organisms that belong within that group.  Below is a chart of some of the characteristics that one can use to understand each eukaryotic kingdom as well as the Domain Bacteria.  You may need to refer to Appendix B to understand the terminology below.

© 2006 STCC Foundation Press, content by Dawn A. Tamarkin, Ph.D.

Last changed: January 21, 2007