Classification

1
Classification
2
Why Classify?
Humans attempt to organize things for easy
identification and reference. . . Biologists
classify to name all organisms and group them in
a logical manner Taxonomy is the science by which
biologists classify organisms and assign each
organism a universally-adopted name -- taxonomy
happens on many levels -- from the
less-specific mammal -- to more specific
dog -- to even more specific golden
retriever
3
Early Taxonomy
Scientists wanted to use a common language, since
every species had a different name in every
language and a different meaning in every
country At first, scientists tried to be as
specific as possible, often giving 20-word long
names to organisms -- this got confusing because
names often included characteristics which some
found relevant and others did not This all
changed with the development of binomial
nomenclature
4
Binomial Nomenclature
In the 18th century, Swedish botanist Carolus
Linnaeus developed a system called binomial
nomenclature In binomial nomenclature each
species is assigned a two-part (binomial)
scientific name (nomenclature) -- the name is
always italicized -- the first word is
capitalized, the second is lowercase ex. Homo
sapiens (human) Ursus arctos (grizzly
bear) The first name is the genus of the
organism The second name is the species of the
organism -- usually the species name is a
Latinized version of some trait
5
Linnaeuss Taxonomic System
In taxonomy, each level of organization is
called a taxon Linnaeus divided the species of
the world into seven taxa, from largest
(most-encompassing) to smallest (one
organism) Kingdom Phylum Class Order Family
Genus Species
6
Kingdom
A kingdom is the most broad level of
classification Species within a kingdom share a
few broad characteristics The most inclusive
level (most species) are classified in a
kingdom When Linnaeus first classified, he named
only two kingdoms, animalia and plantae. Today,
there are 5 kingdoms -- Animalia (animals) --
Plantae (plants) -- Fungi -- Protista
(protists) -- Monera (monerans)
7
Phylum
Phylum is the second-most inclusive taxon Species
within a phylum are all in the SAME KINGDOM but
are linked by a common trait Phyla are still very
broad for example -- mammals, fish, reptiles,
amphibians, and birds are placed in the same
phylum, chordata, simply by the fact that both
have a vertebrate backbone
8
Class, Order, and Family
Class is a smaller subgroup of a phylum, based on
a similar group of characteristics -- for
example, of the phylum chordata, classes include
things like mammals and birds based on physical
appearances and how young are raised Order is a
smaller subgroup of a class, based on an even
more specific characteristic -- for example,
carnivora is a subgroup of the class mammalia,
based on how organisms feed Family is an even
smaller subgroup, based on similar
characteristics -- as you go from class to order
to family, the shared characteristics increase,
and the number of included species decrease
9
Genus
Organisms within a genus share many
characteristics, and may only differ in a few
small features -- for example, all bears are
grouped in the genus Ursus because of the many
characteristics they share The genus is the
first, capitalized word in the binomial
nomenclature of any species Organisms within the
same genus share a recent common ancestor
10
Species
At the species level of taxonomy, there is only
ONE specific type of organism -- each species
has its own species name -- therefore, you have
to go to the genus level of taxonomy to see how
closely species are related -- this is why we
use two words in binomial nomenclature Species
are groups of organisms that have the ability to
interbreed and produce fertile offspring
11
Problems with Linnaeus
Back in Linnaeus time, we classified species on
how they looked and behaved -- this is not
always the best, for example, dolphins and
whales would be classified with fish instead of
mammals Structural comparisons based on
convergent evolution provided quite a problem
with classification Nowadays, we changed our
classification to evolutionary classification
12
Evolutionary Classification
Evolutionary Classification groups organisms
together based on their evolutionary history --
this ensures species of the same genus are more
closely-related than two species with a
different genus We can use certain tools to help
us with evolutionary classification --
similarities in RNA and DNA -- molecular clocks
13
Similarities in RNA and DNA
We look at the sequences of DNA that code for
certain genes to figure out how species are
related -- the more similar the DNA, the more
closely species are related! Similarities in DNA
have led us to solve complicated questions about
evolutionary patterns
14
Molecular Clocks
Because mutations happen at a constant rate, the
amount of differences in DNA between two related
species can tell us how closely two species
shared a common ancestor -- different genes,
however, have different rates of mutations This
allows for construction of a cladogram, which is
read like a phylogenic tree to follow the path of
speciation of an organism
15
Cladogram
Cladograms are charts that show the relationship
between derived characters of different
species -- Derived characters are
characteristics that appear in recent parts of a
species lineage, but not in the past Sample
cladogram
16
Drawing a Cladogram
Draw a cladogram based on the following data