A Familiar
Example:
The US Postal
Service classifies mail in much the same way that scientists classify animals.
If you want to mail a letter to your friend, you use an envelope containing
identifying categories (i.e. the address) to which your friend belongs. These
categories follow a hierarchical system, eventually ending in your friend’s
name. Below the typical address label to reflect the principles used in taxonomic
classification and identification:
KINGDOM
UNITED STATES
PHYLUM
COLORADO
CLASS
DENVER
ORDER
1234 FRIEND
FAMILY
SUITE 123 ABC
GENUS
DOE
SPECIES
JOHN
The scientific
name of this organism would be written as John doe or John doe.
How will you remember these 7 Ranks??
There are many
different pneumonics for remembering the classification
hierarchy, for example, "King Phillip Came Over From Great Spain!!" How well do you know your British history
– what is this pneumonic referring to?
You as an example:
As humans, we
all belong to the following classification scheme:
KINGDOM
ANIMALIA
PHYLUM
CHORDATA
CLASS
MAMMALIA
ORDER
PRIMATE
FAMILY
HOMINIDAE
GENUS
HOMO
SPECIES
SAPIENS**
Our scientific name is Homo sapiens
or Homo sapiens.
The following table shows the classification
of some other organisms:
| Organism
|
Chimpanzee |
Southern
Leopard Frog |
Katydid |
| Kingdom
|
Animalia |
Animalia |
Animalia |
| Phylum
|
Chordata |
Chordata |
Arthropoda |
| Subphylum
|
Vertebrata |
Vertebrata
|
Uniramia
|
| Class
|
Mammalia |
Amphibia |
Insecta |
| Order
|
Primates |
Anura |
Orthoptera |
| Family
|
Hominidae |
Ranidae |
Tettigoniidae |
| Genus
|
Pan |
Rana |
Scudderia |
| Species
|
troglodytes |
pipiens |
furcata |
| Scientific
Name |
Pan
troglodytes |
Rana
pipiens |
Scudderia
furcata |
This table was designed and
created by Dawn M. Kitchen and Tim Susman, University of Minnesota, modified by Cynthia Church
Systematics:
Connecting Classification to Phylogeny
How do we reconstruct evolutionary
history to draw phylogenetic trees (family trees)?
The fossil record helps, of course.
Assessing relationships between living species by comparing their anatomy
also provides data. And we can compare two species at the molecular level
by sequencing their DNA (or protein). But, how do systematists evaluate all
of this info and construct a family tree? Today, most systematists use what
is called cladistic analysis (or simply, cladistics). A phylogenetic tree
based on cladistics is called a cladogram.
Cladogram
While systematics is the reconstruction
and study of evolutionary relationships, classification refers to how we place
species and higher groups in the taxonomic hierarchy. To understand why the
two are not always congruent, we need to consider how species may be grouped
based on their phylogenetic (evolutionary) relationships. A monophyletic
group incudes the most recent common ancestor of the group and all of its
decendants. In the figure below, Taxon 1 (consisting of the seven species
B-H) is a monophyletic group. It is made up of an ancestral species (species
B) and all of its descendant species. A paraphyletic
group includes the most recent common ancestor of the group, but not all its
descendants. Taxon 2 consists of an ancestor (A) and some, but not all, of
that ancestor's descendants (Taxon 2 includes the descendants I and K, but
excludes J and B-H, which are also descended from A). A polyphyletic
group does not include the most recent common ancestor of all members of the
group. Taxon 3 is polyphylectic, which means that it lacks the common ancestor
(B) that would unite the species as monophyletic group. In other words, a
polyphyletic group has members that can be traced to separate ancestors.
Each evolutionary branch in a cladogram
is called a clade (from the Creek clados, branch).
Notice that clades, like taxonomic levels, can be nested within larger clades.
For example, the turtle-leopard clade represents a clade within the salamander-turtle-leopard
clade. But not all groupings of organisms qualify as clades. A clade consists
of an ancestral species and all of its descendants. Such a group of species,
be it a genus, family, or some higher taxa, is said to be monophyletic. Paraphyletic
and polyphyletic taxons are groupings of species that are unacceptable in
the practice of cladistics.
The
Compleat Cladist is a phylogenetic workbook that will give you more practice
with cladistics.
Definitions
Classification – Organization
of organisms into groups or taxa (singular – taxon)
Nomenclature – Assignment of a distinctive name to each species
Taxonomy – General art, craft, and science of classification
Systematics – Modern taxonomy based on evolutionary history
Cladistics – A method of analyzing the evolutionary relationships between
groups to construct their phylogenetic tree (family tree).
Clade – An evolutionary branch in a cladogram; a clade refers to all
the descendants of a particular common ancestor. By definition, a clade is
a monophyletic group.
Humor in Taxonomy
Some whimsical
taxonomic names exist….. Agra vation is a tropical beetle that
was apparently very difficult to collect.
Another insect, a true bug, is named Heerz
lukenatcha.
Organisms are sometimes named after people. A louse that lives on owls has been named
Strigiphilus garylarsoni;
a bacterium bears the name Salmonella mjordan,
named by a microbiologist who is a basketball fan. My advisor named a parasite after his ex-wife.
The names of some amphipod crustaceans exceed 40 letters in length,
such as Polichinellobizrrocomic burlescomagicaraneus.
Return to the Invertebrate Zoology
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