Question

Linnaeus published his classification system in the 1700s. Since then, many new species have been
discovered. The biochemistry of many organisms has also become known.
Eventually, scientists realized that Linnaeus’s system of classification needed revision or changing. A major
change to the Linnaean system was the addition of a new taxon called the _______________________ .
A DOMAIN is a taxon that is _______________________ and more inclusive than the kingdom. Most
biologists agree there are three domains of life on Earth: _______________________ ,
_______________________ , and _______________________ . Both Bacteria and Archaea consist of single-
celled _______________________ .
Eukarya consists of all _______________________ , from single-celled protists to humans. This domain
includes the _______________________ (animals), _______________________ (plants),
_______________________ (fungi), and _______________________ (protists) kingdoms.
QUICK CHECK FOR UNDERSTANDING!
1) Why were revisions made to the Linnaean classification system?
2) What revisions did taxonomists make to the Linnaean classification system?
In summary, classification is an important step
in understanding life on Earth. All modern
classification systems have their roots in the
Linnaean classification system. The Linnaean
system is based on
_______________________ in obvious
_______________________ traits.
It consists of a hierarchy of taxa, from the
kingdom to the species. Each species is given
a unique two-word Latin name. The recently
added _______________________ is a larger
and more inclusive taxon than the kingdom.

Answer 1

Filled answers:

- A major change to the Linnaean system was the addition of a new taxon called the domain.
- A DOMAIN is a taxon that is higher-level (more inclusive) than the kingdom.
- The three domains: Bacteria, Archaea, and Eukarya.
- Both Bacteria and Archaea consist of single-celled prokaryotes.
- Eukarya consists of all eukaryotes, from single-celled protists to humans.
- This domain includes the Animalia (animals), Plantae (plants), Fungi (fungi), and Protista (protists) kingdoms.

Quick check for understanding
1) Why were revisions made to the Linnaean classification system?
- Because many new species were discovered and biochemical/molecular (and evolutionary) evidence showed relationships that morphological traits alone did not reveal; the system needed updating to reflect evolutionary relationships and molecular data.

2) What revisions did taxonomists make to the Linnaean classification system?
- They added the domain as a rank above kingdom and reorganized major groups based on molecular and evolutionary evidence (e.g., splitting prokaryotes into Bacteria and Archaea, recognizing Eukarya and revising kingdom boundaries such as separating Fungi from Plantae and defining Protista).

Final summary blanks:
- The Linnaean system is based on similarities in obvious morphological (structural) traits.
- The recently added domain is a larger and more inclusive taxon than the kingdom.