In the 18th century, Carl Linnaeus published a system for classifying living things, which has been developed into the modern
classification system. Recently the classification system of life was changed to include not five but six kingdoms, as well as
three domains. Earlier classification attempts were based mostly on structural features. Classification of many species, old and
new, continues to be hotly disputed as scientists find new information or interpret facts in new ways. Now, DNA technology
has allowed scientists to re-examine the relationships between organisms to refine the classification system.
The graphic shows a a six-kingdom model published by Thomas Cavalier-Smith in 1998, which has since been revised to a seven
kingdom system. Some of the changes made by Cavalier-Smith were due to advances in the electron microscope that allowed for
the discovery that some chloroplasts were found in the endoplasmic reticulum rather than the cytoplasm. Each statement suggests
a way the 6-kingdom system by Cavalier-Smith differs from the kingdom system, except:
Cavalier-Smith's model adds the Kingdom Chromista
Cavalier-Smith's model no longer separates prokaryotes and eukaryotes.
Cavalier-Smith's model combines Archaebacteria and Eubacteria into one
kingdom, Bacteria
Cavalier-Smith's model reorganizes eukaryotes into five kingdoms instead
of the 4 commonly accepted.