Download Chapter 18

Chapter 18
Classification
Finding Order in Diversity
There are 1.5 million
known species that
have been identified
and classified


Why classify?
How could a scientist
classify living things?
Taxonomy


NO, it is not stuffing a dead animal
It is the logical classification of organisms
based on similarities
Assigning Scientific Names
Name two ways we
can name this large
rodent that burrows
holes in the ground
In America we have
opossums that are
considered ugly and
of no use to humans
In New Zealand,
opossums are highly
regarded for their
beautiful fur and are
often used as a food
source
Binomial Nomenclature
Bi = two
Nomial = name
Designed by Carolus Linnaeus
Each species is given its own two word
name
How to use the bionomial system
The first name is the Genus of the
organism


It is capitalized and italicized
Ex. Ursus
The second name is the Species


It is written in lower case and also italicized
Ex. arctos
Finished Product
Ursus arctos
Linnaeus’s System of
Classification
Hierarchical

Consists of levels
Seven levels

Kingdom, Phylum, Class, Order, Family,
Genus, Species
Kingdom
Most diverse
Largest category
Species
Most specific
Smallest Category
Modern Evolutionary Classification
Which similarities are most important?

In Linnaeus’ time, organisms were grouped
according to physical characteristics
Using the example of a dolphin, how might this be
a problem?
Evolutionary Classification
Phylogeny – evolutionary relationships


Grouping into categories based on
evolutionary descent
Some organisms may look closely related, but
do not share a common ancestor
Group these three
organisms
Although Limpets and Barnacles look very
Similar they have important differences.



Their larvae are unlike each other
Barnacles are segmented, more like a crab
Barnacles, like crabs molt (shed outer layer)
This places barnacles in the category of crustaceans like
crabs and limpets in the category mollusk like clams
Classification Using Cladograms
Derived Characters

Characteristics that appear through evolution
and are not present in older ancestors
Cladogram

Diagram used to show evolutionary
relationships between organisms
Branches show where new characteristics appear
Similarities in DNA and RNA
By comparing genes in different species,
scientists can determine how closely they are
related
Probably the most powerful tool for classification

Ex. P. 454 Vultures and Storks
African vultures and American vultures were once classified
in the same family (falcon)
Recent DNA comparisons show, American vultures are more
closely related to storks
Molecular Clocks
By comparing the number of mutations in
gene sequences of two or more species,
scientists can determine how long ago
they separated
The degree of dissimilarity is an indication
of how long ago two species shared a
common ancestor
There are Three Domains


Domains categorize organisms based on how
long they have been evolving independently
They are larger than kingdoms
Archaea- contains kingdom archaebacteria
Bacteria – contains kingdom eubacteria
Eukarya – contains animals, plants, fungi and
protists
Kingdoms and Domains
There are six Kingdoms






Animal
Plant
Fungi
Protist
Archaebacteria
Eubacteria
Dichotomous Key
Tool used to identify
organisms