Download Classification and Taxonomy Chapter 18

Classification and
Taxonomy
Chapter 18
Ms. Martinez
LSHS
Why Classify?
To
study the diversity of life,
biologists use a classification
system to name organisms and
group them in a logical manner.
Taxonomy is the branch of biology
concerned with identifying and
naming organisms.
By
the eighteenth century, European
scientists recognized that referring to
organisms by common names was
confusing.
Common names vary among
languages and even among regions
within a single country.
For example, a cougar can also be
called a puma, a panther, or a
mountain lion.
Binomial Nomenclature
A
major step to name organisms was
taken by Carolus Linnaeus, a Swedish
botanist who lived during the
eighteenth century.
He developed a two-word naming
system called binomial
nomenclature (by(by-NOHNOH-meemee-ul NOHNOH-munmun-klayklay-chur).
chur).
This system is still in use today.
In
binomial nomenclature, each
species is assigned a two-part
scientific name.
RULES for writing scientific names:
– it is always written in italics
– the first word, the genus, is CAPITALIZED
– and the second word is lowercased
– If handwritten, each term is underlined
For
example:
Ursus arctos (Grizzly bear)
Genus
species
For
example:
Ursus maritimus (Polar bear)
Genus
species
For
example:
Pantera leo (Lion)
The
genus can be
abbreviated!
Ex. U. arctos or U. maritimus
Natural History Museum, Los Angeles 2009
Black rhinoceros
Natural History Museum, Los Angeles 2009
Greater Kudu
Linnaeus's Hierarchical System of
Classification
Linnaeus's
classification system is
hierarchical; that is, it consists of
levels.
Linnaeus's hierarchical system of
classification includes several levels.
They are—from LARGEST to
SMALLEST— Kingdom, Phylum,
Class, Order, Family, Genus, and
Species.
Here
is an easy way to remember
the MODERN levels:
Do Kings Play Chess On Funny Green
Squares?
Do
= domain
Kings = kingdom
Play = phylum
Chess = class
On = order
Funny = family
Green = genus
Squares? = species
In
taxonomic nomenclature, or
naming system, each of those levels
is called a taxon (plural: taxa), or
taxonomic category.
The higher the category, the more
inclusive it is.
Members of taxon share general
characters
Phylogeny
Linnaeus
and other taxonomists have
always tried to group organisms
according to biologically important
characteristics.
Biologists now group organisms into
categories that represent lines of
evolutionary descent, or phylogeny,
not just physical similarities.
Phylogeny is the evolutionary history
of a group of organisms.
A
phylogenetic tree indicates
common ancestors and lines of
descent.
Derived characters can
be used to construct a
cladogram, a diagram
that shows the
evolutionary
relationships among a
group of organisms.
Cladograms are useful
tools that help scientists
understand how one
lineage branched from
another in the course of
evolution.
All of the classification methods discussed
so far are based primarily on physical
similarities and differences.
The genes of many organisms show
important similarities at the molecular
level.
Similarities in DNA can be used to help
determine classification and evolutionary
relationships.
Molecular Clocks:
Biologists compare DNA
sequences to determine
evolutionary
relationships.
The more similar the
DNA sequences of two
species are, the more
recently the two species
shared a common
ancestor.
Each picture in the
diagram represents a
gene.
Each shaded portion of
a gene represents a
mutation.
Classification Systems
Early biologists recognized two kingdoms:
animals (kingdom Animalia) and plants
(kingdom Plantae).
In 1969, R. H. Whittaker suggested a five
kingdom system based on cell type,
organization, and nutrition
In recent years, biologists came to
recognize that the Monera were composed
of two distinct groups and they have been
separated into two kingdoms, Eubacteria
and Archaebacteria, bringing the total
number of kingdoms to six.
Members of Monera (Archaebacteria and
Eubacteria) are prokaryotic bacteria that
obtain organic molecules by absorption or
photosynthesis.
Members of Protista are mainly unicellular
eukaryotes that obtain organic molecules by
absorption, ingestion, or photosynthesis.
The Plantae are multicellular eukaryotes,
autotrophic by photosynthesis.
Members of Animalia are multicellular
eukaryotes, heterotrophic by ingestion, are
generally mobile.
Members of the Fungi are multicellular
eukaryotes, heterotrophic saprotrophs that
form spores, lack flagella and have cell walls
containing chitin.
Domains
Molecular analyses (ex Molecular Clocks)
have given rise to a new taxonomic
category that is now recognized by many
scientists.
The domain is a more inclusive category
than any other—larger than a kingdom.
The three domains are the domain
Bacteria, Archaea, and Eukarya.
The domain
Bacteria
corresponds to
the kingdom
Eubacteria
The domain
Archaea
corresponds to
the kingdom
Archaebacteria.
The domain
Eukarya
corresponds with
kingdoms:
Animalia, Plantae,
Fungi, and
Protista