Classification
of Organisms
Taxonomy
• Taxonomy is the science of naming and
classifying organisms
• Our classification system was first developed
by Swedish botanist Carolus Linnaeus
Binomial Nomenclature
• System developed by Linnaeus
• Each species has a two-part Latin name
– Genus species
– Ex: Tyto alba (barn owl)
Seven Levels of Classification
• Kingdom
– Phylum
• Class
– Order
» Family
• Genus
• Species
King Philip Came Over For
Green Salami
• Animalia
– Chordata
• Mammalia
– Primates
» Hominidae
• Homo
• sapiens
• Binomial nomenclature
name = Homo sapiens
Kingdoms
• Monera
– Single-celled prokaryotes
– Bacteria
• Prostista
– Single-celled eukaryotes
– Algae, amoeba
• Fungi
– Mushrooms, molds, yeast
• Plantae
– Photosynthetic organisms
• Animalia
– Animals
Classification
Which two species are most closely
related?
Cladistics
• Cladistics is classification based on common
ancestry
– Cladogram- family tree (phylogenetic tree)
• Classification is based on physical and genetic
evidence
– Physical evidence: bilateral vs. radial symmetry
– Bilateral: mirror images when divided in half (most
mammals)
– Radial: can be divided into identical halves at any
angle (ex: starfish)
Interpreting Cladograms
• Which organisms are most closely related?
Least related?
Interpreting Cladograms
• Which organisms are extinct?
• Which species is most closely related to the
cape fox?
• Which species developed the most recently?
Cladogram
• Tells us which
characteristics
organisms have in
common.
• Which trait developed
first: jaws or hair?
• What is one organism
that has jaws but no
hair?
Dichotomous Key
• Tools to help us identify species
• Similar to a field guide