Ch 18
Classification
Finding Order in Diversity
Why is it important to classify
organisms?
 To study the diversity of life, biologists
use a classification system to name
organisms and group them in a logical
manner.
 Taxonomy- classification of organisms
with a universally accepted name.

Binomial Nomenclature

A two-word naming
system.
 Developed by Swedish
botanist Carolus
Linnaeus.
 In binomial
nomenclature, each
species is assigned a
two-part scientific name.
(Genus species)
Linnaeus’ System of Classification

Taxon- a group or level
of organization is called a
taxonomic category or
taxon.
 Linnaeus’ system of
classification uses seven
taxonomic categories.
 They are- from smallest
to largest- species,
genus, family, order,
class, phylum, and
kingdom.
Classifications
Species- group of similar organisms that can
breed and produces fertile offspring.
Genus- group of closely related species.
Family- group of genera that share many
characteristics.
Order- group of similar families.
Class- group of similar orders.
Phylum- group of closely related classes.
Kingdom- largest taxonomic group, consisting of
closely related phyla.
Evolutionary Classification

Biologists now group
organisms into
categories that
represent lines of
evolutionary descent,
not just physical
similarities.
 Evolutionary
classification- The
strategy of grouping
organisms together
based on their
evolutionary history.
Classification Using Cladograms

Derived
CharacteristicsCharacteristics that
appear in recent
parts of a lineage
but not in its older
members.
 Cladogram- A
diagram that shows
the evolutionary
relationships among
a group of
organisms.
Similarities
The genes of many organisms show
important similarities at the molecular
level.
 These similarities can be used as criteria
to help determine classification.

dichotomous key
~W~O~R~K T~O~G~E~T~H~E~R
Pg 455
 Questions 1-5
 Don’t write the questions

6 Kingdoms

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Eubacteria- Unicellular and prokaryotic bacteria.
Has thick cell walls that contain peptidoglycan.
Archaebacteria- Unicellular and prokaryotic
bacteria. Live in EXTREME environments.
Protista- Protists. Eukaryotes. Cell walls of
cellulose in some. Some have chloroplasts.
Fungi- Mushrooms, yeasts, and molds. Cell walls
contain Chitin.
Plantae- Plants. Cell walls of cellulose;
chloroplasts.
Animalia- Animals. No cell walls or chloroplasts.
Eubacteria

E-coli
Archaebacteria

Morning Glory Pool
Protists
Fungi
Plantae
Animalae