Classification I: Intro
IB Biology
Classifying Organisms
The science of
classifying organisms is
called taxonomy
The “father of modern
taxonomy” was Carolus
Linnaeus (Carl von
Linné)
Organisms are grouped
into “taxa” based on their
similarities to each other
The Old System
5 Kingdom Classification System:
– Monera: all prokaryotes
– Protista: single-celled eukaryotes (protists)
– Fungi: multi-cellular heterotrophic sessile
eukaryotes
– Plantae: multi-cellular autotrophic sessile
eukaryotes
– Animalia: multi-cellular heterotrophic motile
eukaryotes
The New System
3 Domain System:
– Archaea: prokaryotes; extremophiles
– Eubacteria: prokaryotes; true bacteria
– Eukarya: eukaryotes
Protista
Fungi
Plantae
Animalia
Under Domain and Kingdom
Organisms are grouped into smaller and
smaller groups all the way down to their
species
A species is the most specific grouping
and includes only organisms that can
interbreed with each other and produce
fertile offspring
To remember the grouping order – just
remember:
Classification Taxa
Kingdom
Phylum
Class
Order
Family
Genus
Species
Note: Scientific names are
always written with the first letter
of the genus capitalized, the first
letter of the species lower-case,
and the whole thing underlined in
italics.
Together, these make up a species’
scientific name
Example: Ursus americanus
Common Name: American Brown Bear
Domain Archaea
Formerly part of the kingdom monera
Microbiologists who study bacteria
determined that the DNA of these are
much different from other, true bacteria
Most Archaea live in extreme conditions
(very hot, acidic/basic, sulfurous, etc)
Domain Eubacteria
Formerly a part of the kingdom monera
Name means “true bacteria”
These are the kind of bacteria likely to
make us sick, live in our gut to help us
digest food, or be used in the making of
cheese
Domain Eukarya
Contains all of the eukaryotes (organisms
with a nucleus in their cells)
– Protista
– Fungi
– Plantae
– Animalia
Kingdom Protista
Includes All Protists:
– Eukaryotic
– Unicellular
Animal-Like Protists (protozoans)
– Pseudopods, Ciliates, Flagellates
– Examples: Amoeba, Paramecia, Giardia
Plant-Like Protists (autotrophic)
– Euglenoids, Dinoflagellates, Diatoms,
Green/Red/Brown Algae
Fungus-Like Protists
– Examples: Water molds, slime molds
Kingdom Protista
Amoeba
Paramecium
Water Mold
Euglena
Giardia
Slime Mold
Dinoflagellates Green Algae
Brown Algae
Diatom
Kingdom Fungi
All eukaryotic, multicellular, heterotrophic,
sessile organisms
Includes: molds, mushrooms, rusts,
lichens
Mycorrhizal associations allow plants to
absorb more water and nutrients from the
soil
Kingdom Plantae
All eukaryotic, multicellular, autotrophic,
sessile organisms
Produce their own food from sunlight and
carbon dioxide
Common Phyla:
– Bryophyta (mosses)
– Pteridophyta (ferns)
– Coniferophyta (conifers, like pine trees)
– Angiospermophyta (angiosperms, like
flowering plants
Kingdom Plantae
Bryophyte
(Moss)
Pteridophyte
(Fern)
Pteridophyte
(Fern)
Coniferophytes
(Pine Trees)
Angiosperm;
Dicot
Angiosperm;
Monocot
Kingdom Animalia
All eukaryotic, multicellular, heterotrophic,
motile (most) organisms
Common Phyla:
– Chordata (those with spinal chords)
– Annelida (worms)
– Mollusca (inc. clams, oysters, etc..)
– Arthropoda (crustaceans, insects, spiders)
– Porifera (sponges)
– There are about 40 such Phyla
Human Classification
Domain Eukarya
– Kingdom Animalia
Phylum Chordata
– Class Mammalia
Order Primate
Family Hominidae
Genus Homo
Species Sapien
Dichotomous Keys
Used to help identify unknown specimen
Work by asking yes or no questions whose
answers lead the reader to the correct taxa for
the organism
Simple Example:
1a. Organism has 4 legs
Go to # 2
1b. Organism has more than 4 legs
Go to # 20
2a. Organism has a tail
Go to # 3
2b. Organism has no tail
Go to # 35
3a. Organism has stripes
Bengal Tiger
3b. Organism has no stripes
African Lion
Dichotomous Key
Try this one:
1a. Organism walks on all 4 legs (quadruped)
2
1b. Organism walks on 2 legs (biped)
8
2a. Organism has visible fur
3
2b. Organism has no visible fur
20
3a. Organism lives in warm climates
7
3b. Organism lives in cold climates
4
4a. Organism has brown or black fur
Ursus Americanus
4b. Organism has white fur
Ursus Maritimus