18.1 Finding Order in Diversity
 To study the
diversity of life,
biologists use a
classification system
to name organisms
and group them in a
logical manner.
 Taxonomy
 Common names can be
confusing and vary
between regions.
 Scientists agreed to use
Latin and Greek when
assigning scientific
names to organisms.
 This practice is still
followed today as new
organisms are
discovered.
 Two-word naming
system used in
differentiating a
species
 Genus species
 A genus is a group
of related species.
 Ursus arctos
 Ursus maritimus
 Includes seven levels- from smallest to largest
 Species, Genus, Family, Order, Class, Phylum, Kingdom
 Each level is called a taxon.
 Family
 Genera that share
many characteristics
 Ursidae
 Ursidae Ursus arctos
 Ursidae Ursus
maritimus
 Ursidae Ailuropoda
melanoleuca
 Order
 Broad taxanomic
category composed of
similar families
 Carnivora
 Examples:
 Canidae
 Felidae
 Ursidae
 Class
 Composed of
similar orders
 Mammalia
 Includes
animals that
are warm
blooded, have
body hair,
and produce
milk for their
young.
 Phylum
 Includes many different
organisms that share
important
characteristics
 Chordata
 Mammalia
 Aves
 Reptilia
 Amphibia
 Several classes of fish
 Kingdom
 Largest and most
inclusive level
 Linnaeus started with
only 2- Animals &
Plants
 Now, we recognize 6!
 Plants, Animals,
Protists, Fungi,
Archaebacteria,
Eubacteria.
18.2 Modern Evolutionary Classification
 Organisms determine
who belongs in their
species by choosing
whom they mate with!
 Scientists have
“invented” larger taxa
according to an
organisms
characteristics.
 Strategy of grouping
organisms together
based on their
evolutionary history
 Phylogenyevolutionary
relationships among
organisms
 See Figure 18-7
 Organisms that
appear very similar
may NOT, in fact,
share a common
ancestor.
 Because… natural
selection operating
on species in similar
ecological
environments has
often caused
convergent evolution.
 Only identifies and
considers characteristics
of organisms that are
evolutionary innovations
 New characteristics that
arise as lineages evolve
over time
 Derived Characters-
appear in recent parts of
a lineage but not in its
older members.
 Can be used to
construct a cladogram
 Diagram that shows
the evolutionary
relationships among
a group of organisms
 Useful for helping
scientists
understand how one
lineage branched
from another in the
course of evolution
 Like a “Family Tree”
 All organisms have
DNA to pass on to
future generations.
 The genes of many
organisms show
important similarities
at the molecular level.
 Similarities in DNA
can be used to help
determine
classification.
 Comparison of DNA can be used to mark the passage the
time that two species have been separated on the “family
tree”
 The degree to which genes are dissimilar indicates how far
in the past the two species shared a common ancestor.
18.3 Kingdoms & Domains
 All science adapts to new discoveries.
 In the early days of classification Linnaeus proposed
a 2-kingdom system.
 Today, because of new discoveries, we recognize a sixkingdom system of classification.
Changing Number of Kingdoms
Timeline
Names of Kingdoms
1700s
Plantae
Late 1800s
1950s
1990s
Protista
Monera
Eubacteria
Archeabacteria
Animalia
Plantae
Animalia
Protista Fungi Plantae
Animalia
Protista Fungi Plantae
Animalia
 Molecular clock model analysis has given rise to a new
taxonomic category larger than the kingdoms.
 Domains
Classification of Living Things
DOMAIN
Bacteria
Archaea
KINGDOM
Eubacteria
Archaebacteria
Protista
Fungi
Plantae
Animalia
CELL TYPE
Prokaryote
Prokaryote
Eukaryote
Eukaryote
Eukaryote
Eukaryote
CELL
STRUCTURES
Cell walls with
peptidoglycan
Cell walls
without
peptidoglycan
Cell walls
some with
cellulose
Cell walls of
chitin
Cell walls of
cellulose;
chloroplasts
No cell walls
or
chloroplasts
NUMBER OF
CELLS
Unicellular
Unicellular
Most
Unicellular
Most
Multicellular
Multicellular
Multicellular
MODE OF
NUTRITION
Autotroph or
Heterotroph
Autotroph or
Heterotroph
Autotroph or
Heterotroph
Heterotroph
Autotroph
Heterotroph
Eukarya
 Unicellular
 Prokaryotic
 Thick, rigid cell walls
 Have peptidoglycan
 Corresponds with the
kingdom Eubacteria
 Ecologically diverse
 Some need oxygen
 Some photosynthesize
 Some are free-living
 Some are parasites
 Unicellular
 Prokaryotic
 Cell walls
 No peptidoglycan
 Unique lipids
 Extremophiles
 Hot springs
 Brine pools
 Anaerobic mud
 Kingdom Protista
 Cannot be classified as
animals, plants or fungi
 Most diverse kingdom
 Most unicellular
 Except multicellular algae
 Autotrophs or
Heterotrophs
 Some share
characteristics with
plants, some with fungi
and some with animals.
 Kingdom Fungi
 Heterotrophs
 Feed on decaying
organic matter
 Secrete a digestive
enzyme and absorb
their food
 Multicellular
 Mushrooms
 Unicellular
 Yeast
 Kingdom Plantae
 Multicellular
 Photosynthetic
autotrophs
 Nonmotile
 Cell walls with
cellulose
 Includes mosses, ferns,
cone-bearing and
flowering plants
 Kingdom Animalia
 Multicellular
 Heterotrophic
 No cell walls
 Very diverse
group