Re: how do domains and kingdoms differ?

Jessica,

Taxonomy is a dynamic science, with the boundaries between groups 
constantly changing to integrate new discoveries.  The rate of change has 
accelerated as advanced DNA and biochemical techniques begin to produce 
results.  Occasionally, it becomes necessary to revise not just the 
boundaries between species, but whole taxonomic groupings, even at the 
kingdom level.

The three domain system of biological classification was introduced by 
Carl Woese to reflect his discovery that the prokaryotes comprise two very 
different groups of organisms. In it, all living things are initially 
grouped into three domains. Two of these, the Bacteria and Archaea 
(originally Eubacteria and Archaebacteria), are derived from the kingdom 
Prokaryotes. The third, the Eukarya or Eukaryota, encompasses all 
eukaryotes, including the older kingdoms Animalia, Plantae, Fungi, and 
Protista.

To answer your question, the old kingdoms have been subsumed into a new 
top-level classification system.  Three domains have been placed above the 
kindoms.  

A comprehensive outline of the divisions, with biochemical details for the 
classification of bacteria between the two new domains, can be found at  http://www.cat.cc.md.us/courses/bio141/lecguide/unit1/3domain/3domain.html