Classification of Living Things
Classification of Living Things
 Taxonomy: science of classification
 Branch of biology that names organisms according to
their characteristics, and places them into orderly
groups based on similar characteristics.
 Why ?
Biologists classify living organisms to answer
questions such as:
- How many known species are there?
- What are the defining characteristics of each species?
- What are the relationships between these species?
Aristotle
 Aristotle
 Greek philosopher and
teacher more than
2000 years ago
 The first person to
devise a classification
system-according to
natural environment
(350 B.C.)
Aristotle
PLANTS:
Based on
size of stem
ANIMALS:
Based on
where they lived
John Ray
 17th Century
 Classified according
to characteristics
 Why are there
problems with this???
Limitations of Early Classification
1. Not all organisms fit into Aristotle’s
2 groups (plants or animals)
Ex: Bacteria
Fungi
Images from: http://www.leighday.co.uk/upload/public/docImages/6/Listeria%20bacteria.jpg
http://danny.oz.au/travel/iceland/p/3571-fungi.jpg
Limitations of Early Classification
2. Common names can be misleading
Ex:
A jelly fish isn’t a fish,
but a seahorse is!
Sea cucumber
sounds like a plant
but… it’s an animal!
Image from: http://www.alaska.net/~scubaguy/images/seacucumber.jpg
Limitations of Early Classification
3. Common names vary from
place to place
Ex: puma,
catamount,
mountain lion,
cougar
are all names
for same animal
Image from: http://www4.d25.k12.id.us/ihil/images/Cougar.jpg
Limitations of Early Classification
4. Same organisms
have different
names in different
countries.
Chipmunk
Streifenhornchen (German)
Tamia (Italian)
Ardilla listada (Spanish)
Image from: http://www.entm.purdue.edu/wildlife/chipmunk_pictures.htm
Limitations of Early Classification
Early Solution:
Description of
Organism Using
Latin Names
RED OAK
Quercus foliis obtuse-sinuatis setaceo-mucronatis
“oak with leaves with deep blunt lobes bearing hairlike bristles”
Limitations of Early Classification
 Problem with Latin Name descriptions?
- Names too long and difficult to remember
- Names don’t illustrate evolutionary
relationships
Carolus Linneaus
 Devised a new
classification system
based on morphology
(Organism’s form and
structure)
 Formed a species
 Similar species group
together to form a
genus
(1707-1778)
“Father” of taxonomy and binomial nomenclature
 Use of genus and species names to form
scientific name
 This system is called binomial
nomenclature
 Binomial means two parts
 Nomenclature means system of
naming
 Latin is used-dead language
Binomial Nomenclature
 Binomial Nomenclature: Two name
naming system
 Italicized or Underlined
 1st Name = Genus
 Capitalized
 2nd Name = Species Identifier
 Lower case
Binomial Nomenclature
Vampire bat
Desmodus rotundus
Image from: http://212.84.179.117/i/Vampire%20Bat.jpg
Eastern chipmunk
Tamias striatus
Image from: http://www.entm.purdue.edu/wildlife/chipmunk_pictures.htm
Binomial Nomenclature
Humans
Homo sapiens
Homo sapiens
Image from: http://www.earlylearning.ubc.ca/images/photo_baby.jpg
Robert Whittaker-1969
 5 kingdom system of
naming
 Animalia, Plantae,
Protista, Monera, Fungi
 Levels of classification
from broadest to
narrowest
 KPCOFGS
Kingdom
Phylum
Class
Order
Family
Genus
Species
Kings
Play
Cards
On
Fat
Green
Stools
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Carnivora
Family Felidae
Genus Panthera
Species leo
http://www.vetmed.wisc.edu/dms/fapm/personnel/tom_b/2004-lion.jpg
Modern Taxonomy
 Modern taxonomy involves early naming/classification
system, but with additional kingdom.
 Domain is the most general grouping
Modern Taxonomy
Organizes
living things
in the
context of
evolution
Modern Taxonomy
 Scientists use a variety of information in
order to classify organisms:
1. Chromosome Structure
2. Reproductive Potential
3. Biochemical Makeup/Protein
Comparison
4. Morphology- Homologous Structures
1. Chromosomes
Similar karyotypes suggest closer relationships.
Indicates similar DNA/RNA structure by comparing
base sequences
Human: http://www.nationmaster.com/wikimir/images/upload.wikimedia.org/wikipedia/en/thumb/1/18/300px-Human_karyogram.png
Chimpanzee: Middle School Life Science , published by Kendall/Hunt.
Human- 46 chromosomes
Chimpanzee- 48 chromosomes
Even differences show relatedness
Chimpanzees have 2 smaller chromosome pairs we don’t have
Humans have 1 larger chromosome pair (#2) they don’t have.
Human: http://www.nationmaster.com/wikimir/images/upload.wikimedia.org/wikipedia/en/thumb/1/18/300px-Human_karyogram.png
Chimpanzee: Middle School Life Science , published by Kendall/Hunt.
2. Reproductive potential
 If two organisms can interbreed AND
produce fertile offspring they are
considered of the same species
3. Biochemical makeup
Comparison of macromolecules
such as Proteins
Similar amino acid sequences in
proteins indicate similar
organisms
Macromolecules
4. MORPHOLOGY
Shape and Function
Image from:
http://www.angelfire.com/ab7/evolution12/evolutionclues.html
Morphology
 Homologous Structures:
 Embryological source of similar
structures indicate a possible common
ancestor
 Example: Bat Wing and Human Arm
 P. 262
Morphology
Bat wing
and human arm
develop from
same embryonic
structures
HOMOLOGOUS
STRUCTURES
Morphology
 Analogous Characteristics:
 May have similar function, but different
embryological origin
 Example: Bird Wing and Butterfly Wing
Analogous characteristics evolved separately.
Organisms not necessarily closely related.
ANALOGOUS
STRUCTURES
Bird wing and
butterfly wing
have evolved with
similar function
BUT
different structure
inside.
http://uk.dk.com/static/cs/uk/11/clipart/bird/image_bird003.html
Insects and birds
NOT closely related!
http://www.naturenorth.com/butterfly/images/05a%20tiger%20wing.jpg
I don’t get it?!
Think in terms of structure.
 Analogous characters  the same function
but different underlying structure.
 Homologous characters  different functions, but
similar structure inherited from a common
ancestor. **Important for cladograms!**
Cladistics
 Reflect an organism’s evolutionary history
 Shows evolutionary relationships based on
“shared derived characteristics”
 Cladistic relationships illustrated through the use
of a Cladogram
Phylogeny:
Evolutionary History
Cladogram
 The greater the
number of derived
characters shared
by groups, the
more recently the
groups share a
common ancestor.
Dichotomous Key
 A dichotomous key is used to classify an
organism by physical characteristics. Made
of couplets of opposing meaning.
Domain
Bacteria
Archaea
Eukarya
Kingdom
Eubacteria
Archaebac- Protista
teria
Fungi
Plantae
Animalia
Cell type
Prokaryote
Prokaryote Eukaryote
Eukaryote
Eukaryote
Eukaryote
Cell
structure
Cell walls
with
peptidoglycan
Cell walls
w/o
peptidoglycan
Cell walls of
cellulose in
some; some
have
chloroplasts
Cell walls of
chitin
Cell walls of
cellulose;
chloroplast
No cell walls
or
chloroplast
Number
of cells
Unicellular
Unicellular
Most
unicellular;
some colonial;
some multicellular
Most
Multicellular
multicellular;
some
unicellular
Multicellular
Mode of
nutrition
Autoroph or
heterotroph
Autoroph or
heterotroph
Autoroph or
heterotroph
Heterotroph
Autotroph
Heterotroph
Mushroom,
yeast
Mosses,
ferns,
flowering
plants
Sponges,
insects, fish,
mammals
Examples Streptoccous, Methanogen Amoeba,
E. coli
, halophiles
Paramecium,
slime molds,
giant kelp