Chapter 15 –
Classifying Living Things
High School Biology Class
What is Classification?
The branch of science that names
and groups living organisms into
categories based on their similar
characteristics and evolutionary
history.
Sometimes referred to as taxonomy.
Why is Classification Important?
Every year, thousands of new species are
discovered.
Scientists have identified more than 2
million species of organisms, but estimate
40 million species inhabit the Earth.
Scientists estimate that there may be
millions of species in the tropical rain forest
and an unspecified number living in the
oceans currently undiscovered.
Why is Classification Important?
A Universal System is necessary to
have clear communication among
scientists worldwide.
The system was designed to
eliminate the use of common names
and confusion in the scientific world.
When Was Classification Started?
Organisms were first classified more than 2,000
years ago by the Greek philosopher Aristotle.
He classified things as either Plant or Animal.
He grouped animals into three basic categories
Land Dwellers, Water Dwellers, and Air Dwellers.
He also grouped plants into three categories,
based on differences in their stems.
When Was Classification Started?
As science developed and more was
learned about living things Aristotle's
system was very INADEQUATE.
In the mid-100’s Carols Linnaeus, a
Swedish biologist established a simple
system for classifying and naming
organisms.
Linnaeus developed a hierarchy (a
ranking system) for classifying organisms
that is the basis for modern taxonomy.
When Was Classification Started?
In his system of classification, he ranked
categories from the broadest and most
general (kingdoms) to the smallest and
most specific (species).
Linnaeus also used Latin for the names of
the categories and species because this
was the language of educated people and
not an everyday language that would be
likely to change.
When Was Classification Started?
Additionally, Linnaeus used an
organisms form and its structures to
categorize it.
Linnaeus is called the Father of
Modern Taxonomy because his
system is still being used today.
How Does Classification Work?
By learning the Hierarchy and the
Naming Process the system becomes
more clearly understood.
A) The Hierarchy System
Linnaeus's classification hierarchy
included FIVE levels and modern
scientists have added TWO more
classifications levels.
A. KINGDOM
B. PHYLUM/DIVISION
C. CLASS
D. ORDER
E. FAMILY
F. GENUS
G. SPECIES
A) The Hierarchy System
How can you remember this?
KING PHILIP CAME OVER
FOR GOOD SPAGHETTI.
This Just In…
Scientists have recently added a new
level of classification above the
kingdoms, called the domain name.
Carl Woese, a modern day scientist,
proposes the use of the following
domain names:
Archaea, Bacteria, and Eucarya.
B) The Naming Process
To ensure accurate communication of
information, Linnaeus proposed a
system of scientific naming using
TWO names for each organism.
This naming system is referred to as
Binomial Nomenclature.
B) The Naming Process
The FIRST word (genus) of a
scientific name is a description of the
group of organisms to which the
individual belongs.
B) The Naming Process
The SECOND word (species) of a
name is a general description of the
organism, usually an important
characteristic it contains, or where it is
located.
B) The Naming Process
When we use the Latin name for an
organism, we always capitalize the Genus
but not the species identifier.
We also print the name in italics or
underline them.
The scientific name can be abbreviated.
For example:
1) Homo sapien = H. sapien
2) Canis familiaris = C. familiaris
How Do We Classify Organisms?
When placing an organism into a group
taxonomists consider its:
• Morphology (appearances & behaviors)
• Chromosomal Characteristics (traits)
• DNA/RNA & Amino Acid Sequences (genes)
• Embryological Development (life-cycles)
• Fossil Records (past histories)
All of the above are used to yield reliable
information about the PHYLOGENY or
evolutionary history of an organism.
How Do We Classify Organisms?
Classification is based on the fact that
different degrees of similarities exist among
organisms.
Organisms are similar because the have
descended from common ancestors.
Thus, the more similar organisms are the
more classification categories they belong
together in.
How Do We Classify Organisms?
TWO Approaches:
1)
SYSTEMATICS
(Family Trees) –
show relationships
thought to exist
among groups of
organisms.
How Do We Classify Organisms?
TWO Approaches:
2)
CLADISTICS (Cladograms) – a new system that
uses certain features of organisms called,
shared derived characteristics, to show
relationships.
The Kingdoms of Life
Linnaeus classified all organisms into
TWO kingdoms, Plants and Animals.
Modern scientists use SIX kingdoms.
Kingdom Monera
Archaebacteria and Eubacteria are
sometimes combined together into
one kingdom called Monera.
Together they include the greatest
number of living things on the Earth.
All members are classified as
prokaryotes and reproduce by binary
fission.
1) Kingdom Archaebacteria
The prefix “archae” means “ancient."
Modern Archaebacteria may be directly
descended from the first organisms on Earth.
They are unicellular prokaryotes with distinctive
cell membranes that lack peptidoglycan.
Some are autotrophic, but most are heterotrophic.
Many Archaebacteria live in harsh environments
such as sulfurous hot springs, very salty lakes,
and in anaerobic environments, such as the
intestines of mammals.
2) Kingdom Eubacteria
The prefix “eu” means “true.“
They are unicellular prokaryotes that have
cell membranes that contain peptidoglycan.
Eubacteria are both autotrophs and
heterotrophs.
Eubacteria are most often the bacteria
(germs) that affect your life such as those
involved in tooth decay or food poisoning.
3) Kingdom Protista
Referred to as “The Ash and Trash Kingdom”
Theses organisms are placed here more because
of what they are not than what they are.
The Kingdom Protista contains all eukaryotes that
are not plants, animals, or fungi.
There are more than 50,000 species in the
kingdom which include unicellular and a few
multicellular eukaryotes like Euglena and
Amoebas.
4) Kingdom Fungi
Fungi are eukaryotes and most are multicellular.
The cells of fungi have cell walls that contain a
material called chitin.
These organisms are heterotrophic and obtain
nutrients by releasing digestive enzymes into a
food source. They then absorb their food after it
has been digested by the enzymes.
Fungi act either as decomposers or as parasites in
nature and include molds, mildews, mushrooms,
and yeast.
5) Kingdom Plantae
Plants are eukaryotic, multicellular and
carry out photosynthesis.
The cells of plants have cell walls, that
contain cellulose.
Plant cells are specialized for different
functions, such as photosynthesis, the
transport f materials, and support.
Plants include mosses, ferns,
gymnosperms (cone-bearing plants) and
angiosperms (flowering plants).
6) Kingdom Animalia
Animals are multicellular, eukaryotic and
heterothophic.
Animal cells have no cell walls.
Most members of the Animal Kingdom can
move from place to place. Although some
are permanently attached to surfaces such
as sponges and barnacles.
Animals include fish, birds, reptiles,
amphibians, and mammals (including
humans).
Kingdom Relationships
The kingdom development is thought
to look something like shown below:
Any Questions?
“If you don’t like the way the world is,
you change it. You have an obligation
to change it. You just do it one step at
a time.”
--Marian Wright
Edelman
“The best way to have a good idea is
to have lots of ideas.”
--Linus Pauling