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 is…
A way of grouping objects
 The history of the
together based on similarities
Tomato-1820 Colonel
Robert Gibbon Johnson
 In the beginning---plants were
announced that at noon
grouped based on people who
on September 26, he
ate them—
would eat a basket of
Edible
tomatoes in front of the
Non-edible
Salem NY courthouse—
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.
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
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
Scientific & Common Names
Many organisms have common
names that can be misleading.
Example: a sea horse is a fish,
not a horse.
Also, it is confusing when a
species has more than one
common name.
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


All newly discovered
species are given Latin
names because it is no
longer used
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 similarities in structure, breeding
behavior, geographical distribution,
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 (fy LAH juh nee).
• 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
(kla DIHS tiks).
• 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 call derived traits.
Shared characteristics
 Is a feature that all members of a group have in
common
 Example: hair in mammals or feathers in birds
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
Cladistics
Allosaurus
Velociraptor
Robin
Archaeopteryx
Sinornis
Theropods
Light bones
3-toed foot;
wishbone
Feathers with
Down
shaft, veins,
feathers
and barbs
Flight feathers;
arms as long
as legs
How are living things Classified?
Felix tigerus
Order of Taxa

A group of organisms is
called a taxon (plural, taxa
Mountain
lion

The smallest taxon is
species. Organisms that look
alike and successfully
interbreed belong to the
same species.

The next largest taxon is a
genus—a group of similar
species that have similar
features and are closely
related
Order of Taxa
 Kingdom, Phylum, Class, Order, Family, Genus,
& Species
Can you remember it this way?
 King Phillip Came Over For Graduation
Saturday.
 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)
 **there are 3 domains of life
Eukarya
Domain
Kingdom
Phylum
Class
Animalia
Chordata
Mammalia
Carnivora
Order
Family
Genus
Species
Felidae
Lynx
Lynx Lynx
rufus canadensis
Bobcat
Lynx
Introduction to Classification
3 Domains of Life
The three domain names
are Bacteria, Archaea,
and Eukarya
 All living things seem to
be related by ancestry to
one of these

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
 Consist of prokaryotes named 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
 Most familiar group
 Consist of eukaryotic organisms
 Have true nucleus, complex cellular organelles
 Include Plants, Animals, Fungi, and a variety of
single-celled organisms
6 kingdoms of life
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
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…