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Chapter 17 Classification
• Are you an organized person?
– Consider – do you organize your room?
CDs?
Your clothes? Your school work?
• What would happen if nothing
was organized?
– Would you be able to find anything?
• Why is it necessary to classify?
*Scientists have identified more than
2 MILLION SPECIES OF ORGANISMSBut estimate 40 MILLION SPECIES
inhabit the Earth.
*There may be millions of undiscovered
species, especially microbes, plants &
insects , In the Tropical Rain Forest &
Oceans
*Every year, thousands of new species
are discovered.
I. Biodiversity
• Biodiversity is the variety of
organisms on the earth.
• Considered at all levels from
populations to ecosystems.
• Naturalists have invented several
systems for categorizing
A. Taxonomy
• Taxonomy is the science of describing, naming,
and classifying organisms.
• The branch of biology that names & groups
organisms -according to their characteristics
& evolutionary history.
• A Universal System was designed to Eliminate
the use of Common Names and Confusion in the
Scientific World.
History of Taxonomy
a. Aristotle –Early Classification system
• Greek philosopher more than 2,000
years ago
• Classified things- Plant or Animal
– Grouped Animals into Land Dwellers, Water
Dwellers, and Air Dwellers.
– Also grouped Plants into 3 categories, based
on differences in their Stems.
Naturalists replaced Aristotle’s
classification system
• As modern science developed in the
fifteenth and sixteenth centuries,
Aristotle's system was found to be
INADEQUATE.
• Aristotle's categories
did not work for
all organisms.
• his use of common names
was problematic.
Use of Common Names
•
COMMON NAMES, such as “robin” or “fir
tree”, for organisms created some problems
•
common names varied from one locale to
next & did not describe species accurately.
• Use of long Latin names
•
Used by scientists before 1700’s,- did not
show relationships between species & were
inconvenient, hard to understand.
Describe a problem with each
of these common names
-Starfish -Seahorse -Jelly fish
-Peanut -Catfish
-Tiger shark
How are their names misleading?
Discuss problems when 1
organism has 2 common names
Example- firefly & lightening bug
b. Carl Linnaeus (1707-1778)
“Father of Modern
Taxonomy”
Swedish Naturalist
• Used morphology
(structure & form)
• Grouped organisms
into hierarchical categories
Linnaeus
• Formed “Taxa” (groups of organisms)
• (Used Latin for the Names because it was
the language of educated people)
• System was based on Morphology
which are the STRUCTURAL
SIMILARITIES BETWEEN ORGANISMS
• Series of hierarchical categories
used to show relationships
• Linneaus divided organisms into 2 KINGDOMS:
• PLANTAE & ANIMALIA.
• Then divided each Kingdom into smaller groups.
(Linnaeus's classification hierarchy had 5 levels)
KINGDOM, CLASS, ORDER, GENUS, SPECIES
• EACH LEVEL GROUPS TOGETHER ORGANISMS
THAT SHARE MORE CHARACTERISTICS WITH
EACH OTHER. (general to more specific)
Modern scientists add 2 more classifications levels to
original 5: PHYLUM & FAMILY.
7 Modern Levels of Classification
(From the most general to the most specific)
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species
Species is the smallest, most specific.
Categories get larger, more general.
Kingdom is the largest, least specific
Pneumonic Devices
• Keep Penguins Cool Or Find
Good Shelter
or
• Kennywood Park Can Open For
Good Summers.
or
• King Phillip Comes Over For Good
Spaghetti
Classification Hierarchy of Organisms
3 Domains:
• Most modern system by Carl Woese
• These are Broad groups above the
kingdom level.
Archaea
Bacteria
Eukarya
2. Binomial Nomenclature
“Two
name naming”
• Uses the last 2 categories (the most specific)
to name things.
• Developed by Carl Linnaeus using the
hierarchical system- uses the Genus &
Species for the 2 parts of the name
• Always Capitalize the Genus but Not the
Species Identifier. Both are either
underlined or italicized.
Using Binomial Nomenclature
• Acer rubrum - RED MAPLE TREE
• Acer is the Latin name for Maple (genus)
• rubrum is the Latin word for Red(species)
• Can be Abreviated: A.rubrum.
• HUMANS ARE NAMED: Homo sapiens
• Homo -large brain & upright posture.
sapiens for our intelligence & ability
to speak.
Abbreviated H. sapiens
Additional Categories
• Zoologists-use term “SUBSPECIES”
for variations that may occur in species from
different geographical locations- ie, timber wolf
and the northern timber wolfCanis Lupus ssp occidentalis
• Botanists
– May use the term “division” instead of phylum
– sometimes split species into Subsets known as
VARIETIES. Example: peaches &
nectarines are varieties of Prunus persica var.
• Microbiologists- Bacteria are also
broken into subsets called STRAINS.
Example: Escherichia Coli – some strains are
harmless, even helpful;- live in our intestines,
but strain E. coli 157 is responsible for food
poisoning deaths.
According to the CDC there are an
estimated 73,000 cases of E. Coli
infection every year in the United States.
The typical symptoms are bloody diarrhea
and (if severe) kidney failure. These
symptoms most commonly appear when a
person has eaten undercooked or
contaminated ground beef.
II. Systematics
*The way we group organisms
continues to change, and today these
methods reflect the evolutionary
history of organisms (What’s in their
genes).
This is called Phylogeny.
Systematics
* organizes the diversity of living
organisms in the context of
evolution.
Scientists construct Phylogenic Trees
based on several types of evidence:
1. Fossil Record
2. Morphology
3. Embryology
4. Chromosomes & Macromolecules
1. Phylogenic Trees
• A family tree that shows
evolutionary relationships thought
to exist among organisms.
• Is a hypothesis about the
relationships.
• Is subject to change - as more
evidence is learned.
II. Shared ancestry: Evidences for Evolutionary Relationships
1. Fossil Record
• Fossil Record a useful tool for ancient
organisms.
• Record is incomplete
– Some organisms overrepresented
– Some organisms may be missing
• Need other evidences to verify
phylogenic relationships
Fossils Types:
actual preservation, petrification,
imprints, molds, casts, footprints
• Dated by radioactive
isotopes in fossil or
geological formation in
which fossils are found
• Requires long periods
of time and unusual
conditions for fossil
preservation
II. Shared ancestry: Evidences for Evolutionary Relationships
2. Morphology
• Examine structure & function
• Homologous structures- similar
features that originated from similar ancestors.
(forelimbs on bat, human, penguin)
• Analogous structures- features that
serve similar functions & look alike but
originated from different embryonic tissues.
(wings- on butterfly, bat, hummingbird)
Homologous structures
Comparing the structural features found in different
organisms reveals a basic similarity.
example is the forelimb of mammals - Although function
is quite different, they are similar structurally.
Analogous structures
• We must look at
structures that look &
function the same but
are not derived from
the same embryonic
tissue.
• These features do not
show recent, related
ancestory.
Vestigial structures
• Features which serve no useful function any
longer in the organism.
• Examples: the pelvis bone in the whale,
tailbone & appendix in humans, pelvis & leg
bones in some snakes, etc
II. Shared ancestry: Evidences for Evolutionary Relationships
3. Embryology
• SIMILARITIES IN EARLY
EMBRYOLOGICAL
DEVELOPEMNT OF
VERTEBRATES CAN BE
TAKEN AS ANOTHER
INDICATION THAT
VERTEBRATES MAY
SHARE A COMMON
ANCESTRY.
At the blastula stage, scientists
begin to look for differences in the
ways organisms develop.
Blastula - An early embryonic form produced by
cleavage of a fertilized ovum - a spherical layer of cells
surrounding a fluid-filled cavity.(think of a basketball)
Gastrula -
double-walled stage of the embryo
succeeding the blastula; the outer layer of cells is the
ectoderm and the inner layer differentiates into the
mesoderm and endoderm
Embryology exampleAt the blastula stage- what happens if a scientist
separates a cell from the ball?
• In Vertebrates (animals with a backbone) &
Echinoderms animals like starfish & sand
dollars)- any cell separated can produce a “twin”.
• But blastula cells in a fruit fly cannot- the separated
cells are already specialized to form a part & will die.
• Conclusion- we are more closely
related to starfish than insects
II. Shared ancestry: Evidences for Evolutionary Relationships
4. Chromosomes &
Macromolecules
• Taxonomists compare Macromolecules like DNA,
RNA & Proteins.
• Example- the number of differences in amino acids
is a clue to how long ago 2 species “Diverged”
• In Divergent Evolution- 2 species
become more and more dissimilar.
• Convergent Evolution- Species which
have different ancestors, but have become more
similar
Proteins indicate degree of relatedness.
Differences - Amino Acids in Protein Cytochrome C
Number of different amino acids found in human cytochrome C as opposed to selected organisms
Organism
# of amino acids different
compared to humans
Human
0
Self (Family Hominidae, Order Primates)
Monkey
1
Different family (Pongidae), same order (Primates)
Pig, bovine, sheep
10
Horse
12
Dog
11
Rabbit
9
Chicken, Turkey
13
Duck
11
Rattlesnake
14
Turtle
15
Tuna
21
Different class (Ostheichthys), same phylum (Chordata) poikilothermic
Moth
31
Different phylum (Arthropoda), same Kingdom (Animalia)
Candida fungus
51
Different Kingdom (Fungi)
•
Different order (Carnivora), same class (Mammalia)
Different class (Aves), same phylum (Chordata) homeothermic
Different class (Reptilia), same phylum (Chordata) poikilothermic
(From Atlas of Protein Sequence and Structure, 1967-68 by Margaret O. Dayhoff
Martin (1993).
B. Cladistics
• uses shared, derived characters as
the only criterion for grouping taxa.
• is a newer way to display
relationships which highlights other
differences (shared or derived
chracters)
• Shared characters-
• Derived Characters- are
special features that apparently have only
developed in that group
– like feathers in birds
Cladogram
• Shared derived characters are strong
indicators of common ancestry.
• Diagrams which show derived characters
are called cladograms.
• Cladograms can show non-traditional
conclusions about
which organisms
are “close cousins”.
From this cladogram, we can figure out that
brown bears have more derived characters in
common with sun bears than with dogs &
lesser pandas are more closely related to
racoons than giant pandas.
Cladogram
Dichotomous Key
• A dichotomous key graphically organizes
data. You start with a main idea, split that
into two major pieces. Those pieces are
then split again into two major pieces. You
can continue splitting each piece until you
reach only one possible answer.
• Each set of questions is called a couplet,
& contains instructions for which couplet to
go to next.
Example of Dichotomous Key
Dichotomous Key Use
• Can be used by any one to classify anything.
• Are used by taxonomists to classify organisms.
III. TWO MODERN SYSTEMS OF
CLASSIFICATION
Aristotle classified organisms as either plant or
animal, but today we recognize that many
forms of life are neither
2 Ways to organize (things continue to change)
A. Three Domain System
B. Six Kingdom System
Modern TAXONOMY recognizes
that many organisms are Neither
Plant or Animal.
• Study cellular structure
• Look at ways organisms obtain food:
–Autotroph- Makes own food
(photosysthesis or chemosynthesis)
–Heterotroph- Eats something
3 Domain System
• Compares Ribosomal RNA of different
organisms.
• Most modern system by Carl Woese
• Broad groups
Archaea
Bacteria
Eukarya
3 Domains
1. Archaea = Prokaryotic cells
2. Bactaeria = Prokaryotic cells
3. Eukarya = Eukaryotic cells
There are four kingdoms in Eukarya
* Protista
* Fungi
* Plantae
* Animalia
•
SIX KINGDOMS GROUP ORGANISMS TOGETHER THAT
HAVE SIMILARITIES SUCH AS MAJOR CELLULAR
STRUCTURE, METHODS OF OBTAINING NUTRIENTS,
AND METABOLISM.
The 3 Domains in detail:
• Domain Archaea
– aligns with Kingdom Archaebacteria, are
single-celled prokaryotes that have distinctive
cell membranes and cell walls.
• Domain Bacteria
– aligns with Kingdom Eubacteria, are singlecelled prokaryotes that are true bacteria.
• Domain Eukarya
– Domain Eukarya includes the kingdoms
Protista, Fungi, Plantae, and Animalia.
– All members of this domain have eukaryotic cells.
Domain: Archaea & Bacteria
What are Bacteria?
• Until recently, the term bacteria was used for
all microscopic prokaryotes. But, it turns
out that there are two groups of prokaryotes
that differ from each other in just about every
way except size and lack of a nucleus.
• These are now divided into 2 kingdoms:
– Archaea -(also known as Archaebacteria)
anicient, extreme environments.
– Bacteria- the "true" bacteria (also known as
Eubacteria)
Domain: Archaea & Bacteria
Bacteria• Organisms in the Kingdoms Eubacteria &
Archae are very different from each other.
• Archaebacteria have been found in
temperatures above the boiling point and
in cold that would freeze your blood.
Eubacteria are the “regular” bacteria.
Domain: Archaea, Kingdom Archeabacteria
1. Archeabacteria
• The prefix archae - comes from the Greek Word
"ANCIENT". MAY BE Directly descended from and
very similar to the First Organisms on Earth.
• They Are UNICELLULAR PROKARYOTES with
distinctive Cell Membranes as well as Biochemical
and Genetic Properties that Differ from ALL Other
Kinds of Life.
• Some are AUTOTROPHIC, producing food by
CHEMOSYNTHESIS. Most are HETEROTROPHIC.
Domain: Archaea, Kingdom Archaeabacteria
Archaea:
• Some types are
• A. Methanogens
• B. Themoacidophiles
• C. Extreme Halophiles
Domain: Archaea, Kingdom Archaeabacteria
• Called Extremophiles
• Many Archaebacteria LIVE in HARSH
ENVIRONMENTS such as Sulfurous Hot
Springs, Very Salty Lakes, and in ANAEROBIC
Environments, such as the Intestines of Mammals.
Includes Chemosynthetic Bacteria.
Domain: Bacteria, Kingdom Bacteria
The “true” bacteria
• The first thing you probably think of
when you say this word is “disease”something like strep. throat or maybe
an infection in a cut.
• Most of the bacteria that are disease
causing are Eubacteria.
• NOTE: Only about 1% of bacteria are
disease causing.
Domain: Bacteria, Kingdom Bacteria
• Many bacteria are very helpful organisms.
• Actinomycetes, produce antibiotics such as
streptomycin and nocardicin;
• others live symbiotically in the guts of animals
(including humans) or elsewhere in their bodies,
or on the roots of certain plants, converting
nitrogen into a usable form.
• Bacteria put the tang in yogurt and the sour in
sourdough bread;
• help to break down dead organic matter; & make
up the base of the food web in many
environments.
Domain: Bacteria, Kingdom Bacteria
The true or “Eubacteria”
•
•
•
•
UNICELLULAR PROKARYOTES (No true nucleus)
Are the greatest number of living things on earth.
No membrane bound organelles
Circular double strand of DNA
• “Eu” means true. Eubacteria are the common,
true bacteria- causing strep throat, food
poisioning, tooth decay, fermenting milk into
yogurt, etc.
Domain: Bacteria, Kingdom Bacteria
Classifying bacteria:
• Bacteria occur in 3 basic shapes: cocci,
bacilli & spiral. Many are named by
their shape.
Domain: Eukarya, Kingdom Protista
3. Protists
• Made of a variety of organisms that don’t
“fit” anywhere else. Some are not very
much like the others in this group.
• EUKARYOTIC (has a true, membrane
bound nucleus)
• 50,000 species- many unicellular, some
are like fungi, some like plants or animals.
• Includes protozoans, unicellular algae,
slime molds & water molds
Protists includes slime molds &
protozoans like Euglena,
Paramecium, Ameoba
Domain: Eukarya, Kingdom Fungi
4. Fungi
• Unicellular & multicellular
• HETEROTROPHIC (eats something
else)
–NOT like plants (photosyntheic)
100,000 species include mushrooms,
puffballs, rusts, mildew & molds
Domain: Eukarya, Kingdom Plantae
5. Plantae
• Multicellular & Photosynthetic
Autotrophs (food by photosynthesis)
They are the chief producers of the world.
• Found in all the types of environments:
aquatic algae, amphibian mosses, and
terrestrial ferns and seed-bearing plants.
• 350,000 species identified.
Domain: Eukarya, Kingdom Animalia
6. Animalia
• Eukaryotic, Multicellular
Heterotrophic organisms.
• Most animals are symmetrical
• Movement at some time in
their life cycle.