Introduction

Life is anywhere on earth, you can find living organisms from the poles to the equator, from the bottom of the sea to several miles in the air, from freezing environments to dry valleys. Over around 3.7 billion years or so, living organism on Earth have diversified and adapted to almost every possible environment. All living organism do hare certain similarities, which they probably inherited from a common ancestor. All living organism can replicate, and the replicator molecule is DNA. All living organisms have the ability to convert the information stored in DNA into products used to build things like fats, proteins and carbohydrates.

In the early 1970’s a professor in the Department of Microbiology named Dr. Carl Woese and other scientists began to find evidence for a previously unknown group of prokaryotic organism. These organisms lived in extreme environments - deep sea hydrothermal vents, "Black smokers", hot springs, the Dead Sea, acid lakes, salt evaporation ponds - environments that scientists had never suspected would contain a profusion of life!

Because they appeared prokaryotic, they were considered bacteria and named “Archaebacteria” (ancient bacteria). However, became obvious from biochemical characteristics and DNA sequence analysis that there were numerous differences between these archaebacteria and other bacteria. It was realized that these archaebacteria were more closely related to the eukaryotes than to bacteria. From this work, Dr. Woese proposed that there should be a new caterogy of classification of life - the Domain, a classification category above Kingdom.