Classifying
Organisms
Essential Questions
• What methods are used to classify living things into
groups.
• Why does every species have a scientific name?
Classification
• is the process of grouping things based on their
similarities.
• Biologists use classification to organize living
things into groups so that the organisms are easier
to study.
• There are many different ideas about how to
classify living things.
Early Classification Systems
• The first scientist to develop a
classification system was Aristotle.
Animals
Plants
Presence of “red
blood”?
Environment?
Structure?
Shape and size?
Tree, shrub or
herb?
Size?
384-322 B.C.
Determining Kingdoms
• Carolus Linnaeus classified organisms based
on similar structures into two main groups
called kingdoms.
• After discovering and learning about new
organisms, an American biologist proposed a
five kingdom system for classifying
organisms.
–Monera, Protista, Plantae, Fungi, and
Animalia
Determining Domains
• Classification system of living things is
constantly changing.
• The current method used for classifying
organisms is called systematics. It uses
all the evidence known about the
organism to classify them.
–Cell type, habitat, how it obtains food and
energy, structure and function of features,
common ancestry, and DNA.
Using Systematics
• Organisms are now split into three domains –
Bacteria, Archaea, and Eukarya.
• They are then placed into one of the six kingdoms.
Scientific Names
Binomial Nomenclature is the naming system
for organisms in which each organism is given a
2 part name (Ex. Ursus arctos)
- The first part of the name is the genus.
-group of similar species
- The second part of the name is the species group of organisms that have similar traits and
produce fertile offspring.
- usually describes the organisms behavior
or appearance.
Levels of Organization
Similar species are grouped into one
genus.
Similar genera are grouped into one
family.
Families into orders, then classes, phyla,
kingdoms, then finally domains.
From broadest to most specific:
Domain, Kingdom, Phylum, Class, Order,
Family, Genus, Species
Classification Tools
• A dichotomous key is a series of descriptions
arranged in pairs that lead the user to the
identification of an unknown organism.
Classification Tools
• A cladogram is a branched diagram that shows
the relationships among organisms, including
common ancestors.
Recap:
3 Domains –
Domain Archaea, Domain
Bacteria, Domain Eukarya
These Domains can be
further broken down into 6
Kingdoms
Six Kingdoms
Archaebacteria
• Single-Celled Organisms (Microscopic)
• Lacks organized nucleus and other organelles.
– Prokaryotic
• Autotrophs and
Heterotrophs
• “Archaea” – ancient
– lives in extreme conditions
Eubacteria
• Single-Celled Organisms (Microscopic)
• Lacks organized nucleus and other organelles.
– Prokaryotic
• Autotrophs and
Heterotrophs
• “Eu” – new
– Different chemical makeup
Protist
• Mostly Single-Celled Organisms
– Some are Multicellular
• Organized Nucleus and Organelles (Eukaryotic)
• Autotrophs and Heterotrophs
Fungi
• Mostly Multi-celled Organisms (Eukaryotic)
– Some are One-Celled
• Heterotrophs
Yeast
Mold Spore
Mushroom
Plant
• Multi-celled Organisms
• Autotrophs
– Photosynthesis
• Eukaryotic
– Cell Wall
and Cellulose
Animal
• Multi-celled Organisms
• Heterotrophs
• Eukaryotic