Chapter 15
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15.1 The Invention of the
Linnaean System
• To talk about and to study organisms it is
necessary to give them names
– biologists use a kind of multilevel grouping of individuals
called classification
– the earliest classification scheme categorized living
things as either animals or plants
– the Greeks and Romans grouped similar plants and
animals into basic units called genera (singular, genus)
• early biologists added a series of nonstandardized
descriptions to the genus name to refer to a species
• this created a string of subjective names called a
polynomial
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• A much simpler system than the
polynomial for the naming of organisms
was developed by Carolus Linnaeus
– Linnaeus assigned organisms a two-part
name called a binomial
– he also grouped similar organisms into
higher-level categories based on similar
characteristics
• this would have important, though
unintended, applications to
evolutionary connections
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Figure 15.1 How Linnaeus named two
species of oaks
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(a) Quercus phellos
(Willow oak)
(b) Quercus rubra
(Red oak)
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15.2 Species Names
• Taxon (plural, taxa) is a group of
organisms at a particular level in a
classification system
– the branch of biology that identifies and
names such groups is called taxonomy
– no two kinds of organisms can have the
same name and all names are given in
Latin
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Figure 15.2 Common names make poor labels
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15.2 Species Names
• The scientific name for an organism is
comprised of the two-part binomial
– the first part is the genus, which is
always capitalized
– the second part is the specific epithet
and is not capitalized
– the two words together are written in
italics
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15.3 Higher Categories
• the binomial has been expanded into a Linnaean
system of classification
– genera with similar properties are grouped together into
a family
– families that share similar characteristics are put into
the same order
– orders with common properties are placed into the
same class
– classes with similar characteristics are placed into the
same phylum
– phyla are assigned to one of several gigantic groups
called kingdoms
– kingdoms are sometimes assigned to an additional
level of classification, called domains
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Figure 15.3 The hierarchical system used to
classify an organism
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Domain
Eukarya
Kingdom
Animalia
Phylum
Chordata
Subphylum
Vertebrata
Class
Mammalia
Order
Rodentia
Family
Sciuridae
Genus
Sciurus
Species
Sciurus
carolinensis
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Sciurus
carolinensis
15.4 What Is a Species?
• Since the time of Linnaeus, about 1.5 million
species have been named
– the actual number of species is much greater
– the biological species concept is widely
applied to animals but not as frequently to
plants
• it does not apply to some kingdoms at all
– molecular data are causing a reevaluation of
traditional classification systems
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Figure 15.4 Ray’s definition of species
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Horse
Donkey
Mule
(top left): © Juniors Bildarchiv/Alamy; (top right): © Photodisc/Getty RF; (bottom): © Alamy RF
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15.5 How to Build a Family Tree
• Phylogeny is the evolutionary history of
an organism and its relationship to other
species
• Systematics is the study of and
reconstruction of phylogenetic trees
– it also includes the naming and
classifying of organisms
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• Cladistics is the systematic approach that
infers phylogeny according to similarities
derived from a common ancestor
– derived characters are characters that are
present in a group of organisms that arose
from a common ancestor that lacked the
character
• a clade is a group of organisms, related by
descent, that share a derived character
– by examining the distribution of derived traits
among related organisms, it is possible to
construct a cladogram, a branching diagram
that represents the phylogeny
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Figure 15.5 A cladogram of vertebrate animals
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Lamprey
Shark
Salamander
Lizard
Tiger
Gorilla
Human
Bipedal
No tail
Hair
Amniotic
membrane
Lungs
Jaws
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15.5 How to Build a Family Tree
• Cladograms convey comparative information
about relative relationships
– organisms that are closer together on a
cladogram simply share a more recent
common ancestor than those that are farther
apart
– each cladogram must have an outgroup, a
rather different organism to serve as a basis
for comparisons among the other organisms
being evaluated, called the ingroup
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15.5 How to Build a Family Tree
• Cladistics is a relatively new but popular
approach to studying evolution because it
is objective and portrays the order in which
a series of evolutionary events have
occurred
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15.5 How to Build a Family Tree
• An alternative approach to constructing
phylogenies is traditional taxonomy
– both ancestral and derived characters
are used to build trees
• the wealth of additional information
allows the weighting of biologically
significant characters, but this is a
more subjective process than
cladistics
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Figure 15.6 Two ways to classify terrestrial
vertebrates
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Class Reptilia
Class
Mammalia
Mammals Turtles
Mammalia
Archosaurs
Class Aves
Crocodilians
Reptilia
Lizards and
snakes
Birds
Mammals
Turtles Crocodilians
Birds
Dinosaurs
Lizards and
snakes
Dinosaurs
Early reptiles
Traditional phylogeny and taxonomic classification
Cladogram and cladistic classification
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Figure 15.7 The cat family tree
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Domestic cat, African
wildcat, black-footed
cat, Chinese mountain
cat, European wild cat,
jungle cat, sand cat
Domestic cat
Leopard cat, flat-headed cat, fishing cat
Mountain lion (also Cheetah
called cougar or puma)
Bobcat, Canadalynx,
Eurasian lynx, Spanish lynx
Bobcat
Canada lynx
Ocelot, Andean mountain
cat, Geoffroy's cat,
kodkod, margay, oncilla,
pampas cat
Ocelot
Caracal, African golden cat
Caracal
Bay cat, Asiatic golden cat
Snow leopard and
clouded leopard
Snow leopard
Tiger
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Lion
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Leopard
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Jaguar
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Millions of years ago
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(cat, cheetah, lynx, tiger, lion, leopard): © Corbis RF; (puma, bobcat, ocelot, caracal, snow leopard, jaguar): © Getty RF
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15.6 The Kingdoms of Life
• Classification systems have gone through
their own evolution of sorts
• Most biologists now use a six-kingdom
system of classification first proposed by
Carl Woese
– four kingdoms consist of eukaryotes
• Animalia, Plantae, Fungi, and Protista
– two kingdoms consist of prokaryotes
• Archaea and Bacteria
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• Recognizing that there are further
differences among the prokaryotes, the
domain level above kingdom was created
– Domain Archaea contains only one kingdom
– Domain Bacteria contains only one kingdom
– Domain Eukarya contains the four eukaryotic
kingdoms
• Because of this, the kingdom level of
classification for Bacteria and Archaea is
now often omitted
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Figure 15.9 Different approaches to
classifying living organisms
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Plantae
Animalia
(a) A two-kingdom system—Linnaeus
Monera
Protista
Fungi
Plantae
Animalia
Protista
Fungi
Plantae
Animalia
(b) A five-kingdom system—Whittaker
Bacteria
Archaea
(c) A six-kingdom system—Woese
Bacteria
Archaea
Eukarya
(d) A three-domain system—Woese
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Table 15.1
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TABLE 15.1
CHARACTERISTICS OF THE SIX KINGDOMS
Domain
Bacteria
Archaea
Kingdom
Bacteria
Archaea
Cell type
Prokaryotic
Prokaryotic
Eukaryotic
Eukaryotic
Eukaryotic
Eukaryotic
Nuclear
envelope
Absent
Absent
Present
Present
Present
Present
Mitochondria
Absent
Absent
Present or absent
Present
Present or absent Present
Chloroplasts
None
None
Present in
(photosynthetic
(bacteriorhodopsin some forms
membranes in some in one species)
types)
Present
Absent
Cell wall
Present in most;
peptidoglycan
Eukarya
Protista
Plantae
Fungi
Animalia
Absent
Present in most;
polysaccharide,
glycoprotein, or
protein
Present in some
forms; various
types
Cellulose and other Chitin and other
polysaccharides
non cellulose
polysaccharides
Absent
Means of
Conjugation,
genetic
transduction,
recombination, transformation
if present
Conjugation,
transduction,
transformation
Fertilization
and meiosis
Fertilization
and meiosis
Fertilization
and meiosis
Mode of
nutrition
Autotrophic
(chemosynthetic,
photosynthetic) or
heterotrophic
Autotrophic
(photosynthesis
in one species) or
heterotrophic
Photosynthetic or
heterotrophic or
combination of
both
Photosynthetic,
Absorption
chlorophylls a and b
Motility
Bacteria flagella,
gliding, or
nonmotile
Unique flagella in
some
9+2 cilia and
None in most forms, Nonmotile
flagella; amoeboid, 9 + 2 cilia and
contractile fibrils
flagella in gametes
of some forms
9 + 2 cilia and
flagella, contractile
fibrils
Absent
Absent in
most forms
Present in all forms
Multicellularity Absent
Fertilization
and meiosis
Present in all forms Present in most
forms
Digestion
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15.7 Domain Bacteria
• The bacteria are the most abundant
organisms on earth-More bacteria living in
your mouth then mammals living on earth
– there are many different types of bacteria and
the evolutionary links between them are not
well understood
• most taxonomists recognize 12 to 15 major
groups of bacteria
• although archaea are also prokaryotic like
bacteria, the archaea are more closely
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related to eukaryotes
15.8 Domain Archaea (ancient)
• The Archaea branched off from a line of prokaryotic
ancestors that lead to the evolution of eukaryotes
– modern Archaea live in some of the most
extreme environments on earth and, although a
diverse group, share some of the same key
characteristics
• their cell walls lack the peptidoglycan that is
characteristic of bacterial cell walls
• they possess unique lipids and rRNA
sequences
• some genes in the archaea have introns
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15.8 Domain Archaea
An intron is a nucleotide sequence within a
gene that is removed by RNA splicing while
the final RNA product of a gene is made.
Exons in DNA become mRNA in
transcription then is translated with tRNA
into a protein.
So exons are used in final product and
introns are not.
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Figure 15.10 A tree of life
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BACTERIA
Purple bacteria
Cyanobacteria
Flavobacteria
ARCHAEA
EUKARYA
Halobacterium Entamoebae
Gram-positive
Methanobacterium
bacteria
Slime molds
Thermoproteus Methanococcus
Pyrodictium
Thermococcus
Animals
Fungi
Thermoplasma
Plants
Ciliates
Methanopyrus
Thermotoga
Flagellates
Microsporidia
Aquifex
Diplomonads
Common ancestor
Base was made by examining genes duplicated in all three domains
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That duplication happened in the common ancestor (presumably)
15.8 Domain Archaea
• Archaea are grouped into 3 general categories
• methanogens obtain their energy by using
hydrogen gas (H2) to reduce CO2 to
methane gas (CH4) 4 H + CO → CH + 2 H O
2
2
4
2
– extremophiles are able to grow under extreme
conditions, such as extreme heat, salt
(Halophites), pH, or pressure
– nonextreme archaea grow in the same
environments that bacteria do (differing in DNA
sequence)
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15.9 Domain Eukarya
• Eukaryotes have a complex cellular
organization but are fairly uniform in
metabolism, when compared to
prokaryotes
– there are three largely multicellular
kingdoms (fungi, plants, and animals)
– the remaining eukaryotic kingdom,
Protista, is a diverse array of mostly
unicellular forms that basically don’t fit
into the other kingdoms
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15.9 Domain Eukarya
• Endosymbiosis may explain the origin of
some eukaryotic organelles
Figure 15.11 Endosymbiosis
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Early eukaryotic cell
Bacterium
Endosymbiosis
(a)
(b)
b: © OSF/Animals Animals-Earth Scenes
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• https://www.youtube.com/watch?v=Q9Ks474dxA
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