Introduction to Taxonomy


Five (More or Less) Kingdoms

NOTE: The monerans are accessed as either eubacteria or archaebacteria. The protists probably represent at least three kingdoms, but cluster under a single click. I didn't know what to do with the ediacarans, but since they don't seem to be direct relatives of the animals, I gave them Kingdom status. NEWS FLASH! Recent research (3 Jan 2008) suggests that the ediacarans may be related to the Cnidaria.

The Mars rock was discovered on the Allan Hills ice field in Antarctica in 1984. The composition of the gas trapped in the rock is a close match to known Martian atmosphere and shows that the rock came from Mars. The rock is approximately 4.5 billion years old and there is evidence that water seeped into the rock ca. 3.6 billion years ago. The rock remained buried on Mars until 16 million years ago when an asteroid striking Mars' surface blaster it into space. It fell to earth 13,000 years ago.

SEM of beasties, carbonate and magnetite crystals normally associated with life on earth. The size of the rod- and spherically-shaped objects are similar in size to archaean bacteria.


Comparison of a Eubacteria cell (E. coli) with Archaebacteria.

 

Black smokers support a variety of archaea. The discovery of the archaea in extreme environments suggests that life evolved under hellish conditions.


Other examples of Archaean habitats.


Vents and relation to 3 domains

Major events that may have occurred at hydrothermal vents. Initially, the first cells are thought to have been a component of the geothermal system (i.e., actually part of the rock without cell membranes). The first pathways developed in these "organisms". As the geothermal-coupled protocells differentiated into free, individual cells the first of the archaea evolved (probably iron sulfide metabolizing thermophiles). This seed later serves as the progenitors of the eubacteria (true bacteria) and eucarya (eucaryotic cells)

Three Domain Theory: Organisms are divided into three groups based on genetic analysis. The Archaea include all the "simple" extremophiles. Some are found in such extreme environments (such as miles below the earths surface) that they are known only by their DNA (pSL 50, etc.). The Bacteria are a separate domain that include typical bacteria (E. coli, etc.). Both the Archaea and Bacteria are classified as prokaryotes because, among other things, they lack membrane-bound organelles. Note that mitochondria and chloroplasts are included within this domain because, while they are organelles within the Bacteria Domain, genetic analysis indicates that they are more related to the Bacteria . The Eukaryota include organisms that have organelles such as mitochondria, chloroplasts, and a nucleus. Click on the "branches" for examples.

Click on Taxonomic levels and/or individual taxa for information. Note that by the time you get down to individual species, a binomial naming system is used. The binomial naming system was proposed by Carl Linnaeus in 1760. Since the species names are based on Latin terminology, they are italisized. If you can't write in italics the names should be underlined.