Classification of Organisms
Classifying Organisms
 One important branch of biology investigates
biodiversity, the variety of organisms considered
at all levels from populations to ecosystems.
 Since the early 1980’s Terry Erwin & others have
been working to catalog insect species in plots of
tropical rain forest
They fog the treetops with insecticide & catch the
falling insects in a net
Classification
Classification is a way of
 The history of the
grouping objects together
Tomato-1820 Colonel
based on similarities
Robert Gibbon Johnson
announced that at noon
 In the beginning---plants were
on September 26, he
grouped based on people who
would eat a basket of
ate them—
tomatoes in front of the
Edible
Salem NY courthouse—
Non-edible
aka “love apple”

Scientists Who Developed
Classification
Aristotle: Greek Philosopher

Developed 1st method of
classification
Classified into 2 major
groups
1. Plants: herbs, shrubs or
trees
2. Animals: According to
where they lived: land,
water or air

Carolus Linnaeus
Swedish naturalist
 Methods still used today
 Selected physical
characteristics based on close
relationships of organisms
 Each category represents a
level of grouping from larger,
more general to smaller, more
specific categories

Plants: based on
reproductive structures
 Animals: based on
evolutionary traits

Carolus Linnaeus
Invented the 2-word
naming system to
identify species
 called BINOMIAL
NOMENCLATURE:
Bi (2) Nomial (name)

Scientific Name:
1. Genus: 1st word:
consist of closely
related species
2. Species: 2nd word:
consist of description of
the species.

RULES OF BINOMAL
MONEMCLATURE
Genus is ALWAYS
capitalized & is 1st
2. Species is ALWAYS
lowercase & is 2nd
3. BOTH ARE
ITALICIZED OR
UNDERLINED!!!
1.
Examples:
Homo sapiens
Felix tigerus
F. leo
F. domestica
SPECIE
 Species names come from Latin roots and are
needed to be the same for all countries and in
every language
 The name of a species is often descriptive and
very specific
 All newly discovered species are given Latin
names because it is no longer used
Subspecies
 Biologists refer to variations of a species that live
in different geographic areas as subspecies
 A subspecies name follows the species identifier
Subspecies: Alabama Beach Mouse
This mouse is one of several
subspecies of old field mice which
live only in coastal sand dune areas.
Living isolated from other beach mice
for thousands of years has allowed
each subspecies to develop its own
slightly unique characteristics suited
to its particular beach environment.
Peromyscus polionotus ammobates
Other Subspecies: Perdido Key beach mouse, Choctawhatchee beach
mouse, Santa Rosa beach mouse, and St. Andrews beach mouse. They
differ from the ABM and each other in coloration and body size
Subspecies identifier
Common Names
Do not tell you how
organisms are related or
classified
 Can be misleading
 Confusion can occur
when organisms have
more than one name

bearcat
Taxonomy is…
Taxonomy (tak SAH nuh mee) is the branch of biology
that groups and names organisms based on studies of
their different characteristics
 Biologists who study taxonomy are called taxonomists

Taxonomists
 Is a useful tool – if a child has eaten a
mushroom & You do not know whether it is
poisonous…
 Important to the economy- often discover new
sources of lumber, medicines & energy…
Dichotomous Key


Organisms can be identified
easily by using a
dichotomous key
Animals around the world
use the same identification
system

A key is made up of sets of
numbered statements. Each
set deals with a single
characteristic of an organism,
such as leaf shape or
arrangement
Using a dichotomous key to identify
money!
Systematic

More than 200 years ago, Linnaeus grouped organisms
according to similarities that he could readily see.
Modern biologists consider not only visible similarities,
but also similarities in embryos, chromosomes, proteins,
and DNA
 Systematics is the classifying of organisms in terms of
their natural relationships

Cladistics
 In 1966, Willi Hennig developed
cladistics, a system of
phylogenetic analysis that uses
shared or derived characteristics
as the only criteria for grouping
taxa
How are evolutionary
relationships determined?
• Evolutionary relationships are determined on
the basis of
1. structural similarities,
2. breeding behavior
3. geographical distribution
4. chromosomes and biochemistry.
The presence of many shared physical structures implies that
species are closely related and may have evolved from a
common ancestor.
1. Structural similarities
• For example, plant taxonomists use structural
evidence to classify dandelions and sunflowers in
the same family, Asteraceae, because they have
similar flower and fruit structures.
• Taxonomists observe and compare features
among members of different taxa and use this
information to infer their evolutionary history.
2. Breeding Behavior
• Sometimes, breeding behavior provides
important clues to relationships among species.
• For example, two species of frogs, Hyla versicolor and Hyla
chrysoscelis, live in the same area and look similar. During the
breeding season, however, there is an obvious difference in
their mating behavior.
•Scientists concluded that the frogs were two separate
species.
Gray Treefrog
Gray Treefrog
3. Geographical Distribution
Crushing
Bills
Probing
Bills
Grasping
Bills
Parrot
Bills
Ancestral Species
Geographical distribution
• These finches probably spread into different
niches on the volcanic islands and evolved
over time into many distinct species. The fact
that they share a common ancestry is supported
by their geographical distribution in addition to
their genetic similarities.
4. Chromosomal Comparison
• Both the number and structure of chromosomes,
as seen during mitosis and meiosis, provide
evidence about relationships among species.
•For example, cauliflower, cabbage, kale, and broccoli
look different but have chromosomes that
are almost identical in structure.
• Therefore, biologists propose that these plants
are related.
Phylogenetic Classification: Models
• The evolutionary history of a species is
called its phylogeny (a tree of life)
• A classification system that shows the
evolutionary history of species is a
phylogenetic classification and reveals
the evolutionary relationships of species.
Cladistics
• One biological system of classification that is
based on phylogeny is cladistics
•Organisms are classified based on shared
derived characteristics
• Scientists who use cladistics assume that as
groups of organisms diverge and evolve
from a common ancestral group, they retain
some unique inherited characteristics that
taxonomists like derived traits.
EX: Shared characteristics
 Is a feature that all
members of a group
have in common
 Ex: Certain animals
are mammals but
the leopard and
house cat are
related due to the
ability to purr
Cladogram
Derived characteristics
 Is a feature that evolved only within the group
under consideration
 Example: feathers are though to be a derived
characteristic for birds b/c scientists hypothesize
that feathers evolved only within the bird lineage
and were not inherited from the ancestors that
birds share with reptiles
How are living things Classified?
Felix tigerus
Order of Taxa

A group of organisms are
called a taxa
Mountain
lion

The smallest taxa is species.
Organisms that look alike
and successfully interbreed
belong to the same species.

The next largest taxa is a
genus—a group of similar
species that have similar
features and are closely
related
Order of Taxa
 Domain, Kingdom, Phylum, Class, Order,
Family, Genus, & Species
Can you remember it this way?
 Do Kings Play Chess On Fine Glass Surfaces?
Important Facts
 Linnaeus version of hierarchy of organization
was made of only 2 kingdoms-animals & plants
 Modern biologists adopted his system, but
added several other kingdoms, as well as
domains (categories above kingdoms)
3 Domains of Life
The three domain names
 1. Bacteria
 2. Archaea
 3. Eukarya
 All living things seem to
be related by ancestry to
one of these

Woese and the 6 Kingdoms
 Biologists Carl Woese proposed in 1977 a 6-
kingdom system that divided the then 5 kingdom
into two new kingdoms; Archaebactera and
Eubacteria
 In 1990, Woese introduced
the 3 domain system that is
still used today
The three domains in the tree of life:
Bacteria, Archaea, and Eukarya
 Domains are above the kingdom level.
proposed by Carl Woese based on rRNA studies of
prokaryotes
domain model more clearly shows prokaryotic diversity
• Domain Bacteria
– Include prokaryotes in
the Kingdom Bacteria
– one of largest groups
on Earth
– classified by shape,
need for oxygen, and
diseases caused
Domain Bacteria
 Is made of small, single-celled prokaryotic
organisms
 Usually have a cell wall & reproduce by cellular
reproduction
 Each bacteria has a cell wall, plasma
membrane, cytoplasm (that lacks organelles)
 Do not have a true nucleus
 Oldest known fossils appear as bacteria
• Domain Archaea
– Includes prokaryotes in the
Kingdom Archaea
– cell walls chemically
different from bacteria
– differences discovered by
studying RNA
– Known for living in extreme
environments
Domain Archaea
 Have distinctive cell membranes, & genetic
properties
 Some are autotrophs
 Some produce methane (as waste)
 Many inhabit harsh environments (sulfur
springs, deep-sea thermal vents, salty lakes…)
 Thought to be the earliest organisms on Earth
• Domain Eukarya
Includes all Eukaryotes
– Kingdom Animalia
– Kingdom Plantae
– Kingdom Protista
– Kingdom Fungi
Domain Eukarya
 Most familiar group
 Have true nucleus, complex cellular organelles
Taxonomic rankings
 Compare the appearance of a lynx
 Lynx rufus- a bobcat,
 Lynx canadensis- Lynx
 Panthera concolor-Mountain Lion
Mountain
lion
Lynx
Bobcat
Eukarya
Domain
Kingdom
Animalia
Chordata
Mammalia
Carnivora
Phylum
Class
Order
Family
Genus
Species
Felidae
Lynx
Lynx Lynx
rufus canadensis
Bobcat Lynx
Classification is always a work in progress.
 The tree of life shows our most current understanding.
 New discoveries can lead to changes in classification.
Until 1866: only two kingdoms,
Animalia and Plantae
– 1866: all single-celled
organisms moved to
kingdom Protista
Plantae
Animalia
Protista
– 1938: prokaryotes moved
to kingdom Monera
– 1959: fungi moved to
own kingdom
Archea
Fungi
Bacteria
– 1977: kingdom Monera
split into kingdoms Bacteria and Archaea
Introduction to Classification
6 kingdoms of life
6 Kingdoms of Life
Kingdom Eubacteria
 Aligns with the domain Bacteria
 Eubacteria means “true bacteria” because it
distinguishes this group from archaea which are
no longer considered to be bacteria
Blue-Green Bacteria
Kingdom Archaebacteria
 Aligns with the domain Archaea
 Archaebacteria means “ancient
Bacteria”
 Are found in extreme habitats
where there is usually no oxygen
available
Dead
Sea
Thermal Vents
Kingdom Protista
 Eukaryote that
are not
plants, animals or
fungi.
 Unicellular organisms
 Examples are
amoebas,
paramecium,
euglenas, Seaweed,
Diatoms…
Kingdom Fungi
Unicellular or multi-cellular
eukaryote that absorbs
nutrients from organic
materials in the environment
 There are around 70,000
species of fungi
 Include puffballs, mushrooms,
rusts, smuts, mildew, and
molds.

Kingdom Plantae
Consist of eukaryotic,
autotroph, multicellular
plants that contain
chloroplasts, use
photosynthesis and have
cell walls
 There are more than
250,000 known species
of plants

Kingdom Animalia
Animals are eukaryotic,
multicellular heterotrophs that
develop from embryos
 Most have symmetrical body
organization & move around
their environment to find food
 Nearly all are able to move
from place to place.
 Animal cells do not have cell
walls

Future taxonomic systems
 Because taxonomy systems are changing,
modern biologists are suggesting changes for
the now six-kingdom, three-domain system
 Suggestions like subkingdoms…