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Principles of Taxonomy
(chapter 18, page 446)
Taxonomy is the science of classifying organisms
based on their characteristics.
Why is a system of classification needed?
a.
Organize species into groups and
discuss them.
b.
Identify new organisms.
c.
Show relationships between
organisms.
We use a system of classification developed by
Carolus Linnaeus (1707-1778) called the
Linnaeus system.
Classification
Linnaeus’s System of Classification now includes
eight levels:
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Dazzling Kinky People Can Only Fake Good Sex
Classification
The system is
hierarchal.
This example is for
the species
panthera pardus,
Taxonomy
When scientists are referring to organisms they
do not have to use all seven levels, just the last
two. This is the way organisms are named in
science.
The system of naming organisms using 2 names,
the genus and the species, is called the binomial
system (also called binomial nomenclature) and
was also developed by Linnaeus.
Using the binomial system avoids the confusion
caused by organisms with different common
names in different areas.
Binomial nomenclature
• Use the genus (or the first letter of the genus),
capitalized, and the species.
ex. Castor canadensis or C. canadensis
• The species name is not capitalized and
cannot be used alone. e.g., C. canadensis.
• If you are handwriting the name, underline it.
• If typing the name, put it in italics.
The 2 part name gives clues about
relationships between organisms. (For
instance, Ursus americanus, U. horribilis, U.
arctos, and U. maritimus are all related.)
Classification based on modern
technology
• Classification used to be based largely on
physical appearances but modern taxonomists
use genetic information, molecular biology,
and phylogeny (evolutionary relationships) as
criteria for classifying.
• The work of Charles Darwin introduced the
idea of considering evolutionary history.
So, what is a species?
• Capable of reproducing fertile offspring with
one another. (Individuals from different
species do not generally reproduce with one
another)
Horse + Donkey = mule or hinnie
Mule + Mule = 0
• Individuals within a species may look quite
different (Think about the many Canus
familiaris)
How many species are there?
• Estimates on the number of eukaryotic species
range from 2 million to 10 million species on
the planet although about 1.4 million species
(eukaryotic) are currently named and
described.
• It is much more difficult to estimate the
number of prokaryotic species, although it is
believed that there are many millions (more
than eukaryotic).
Kingdoms/domains system
pages 457 to 461
Originally there were only two kingdoms
recognized by Linnaeus: animals and
plants.
• Later, these two were divided into five:
animals, plants, fungi, protista, and monera
(bacteria).
• Now, most people, including Bio 112 students,
recognize 6 kingdoms and 3 domains.
Now there are 6.
Recent research using DNA analysis has shown
how groups of organisms are more similar
than can be observed by the “naked eye”.
Evolution of organisms has been traced,
relationships among organisms found.
This has been used to place organisms into
“domains” (right above Kingdoms).
Cladogram
Biologists now group organisms into
categories based on lines of evolutionary
descent, called phylogeny, not just on physical
characteristics.
These evolutionary relationships are shown in
cladograms. Page 452.
• https://www.youtube.com/watch?v=H6IrUUD
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3 Domains: bacteria, archaea and eukarya.
• 6 kingdoms:
eubacteria, archaebacteria, protista, fungi, plantae,
animalia
• Look at the chart on page 459 and read pages
458 to 461.
• You are required to know which Domain each
Kingdom is in and the general characteristics
of members of each Kingdom. (See the chart)