CHAPTER 10
Taxonomy and
Phylogeny of
Animals
10-1
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10-2
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Linnaeus and Taxonomy
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More than 1.5 million species of animals are
named
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Estimated that these account for
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Taxonomy (aka - Systematics)
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Less than 20% of all animals currently alive
Less than 1% of extinct animals
Formal system for naming and classifying species
Science of classifying organisms based on
similarity, biogeography, etc.
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Systematics
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3 types of Systematics/Taxonomy
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Evolutionary Systematics
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Numerical Taxonomy
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Grouping organisms that resemble ancestors
Used mathematical models to group organisms
according to overall similarities
Phylogenetic Systematics (cladistics)
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Use “outgroups”, differences between taxa to make a
subset called a clade (Greek - branch)
Most commonly used, measures variety of
characteristics. *Discussed later*
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Linnaeus and Taxonomy
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Greek philosopher Aristotle first classified
organisms (350 BC)
Carolus Linnaeus designed the current
system of classification (1750)
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Swedish botanist with extensive experience
classifying objects, especially flowers
Used morphology (study of form and structure) to
develop a classification system of animals and
plants
Divided animal kingdom into species and gave
each a distinctive name
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10-5
Grouped species into genera, genera into orders, and
orders into classes
His classification scheme has been drastically
altered, but the basic principle is still followed
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Carolus
Linnaeus
10-6
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Linnaeus and Taxonomy
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Hierarchy of taxonomic ranks now includes 7 major
groups
 Kingdom, phylum, class, order, family, genus, and
species
Now, the new level of Domain is also used.
All animals are placed in Kingdom Animalia, or
Domain Eukarya
Taxa (Taxon) - Groups of animals that share a
particular set of characteristics.
 Example: True Flies “Diptera” - single pair of
wings
 Each rank can be subdivided into additional levels
of taxa
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Superclass, suborder, etc.
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10-8
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Division of Life - Milestones
Linnaeus
1735
2 ki ngdoms
(not treated)
Haeckel
1866 [5]
3 ki ngdoms
Protista
Chatton
1937 [6]
2 em pires
Copela nd
1956 [7]
4 ki ngdoms
Whittaker
1969 [2]
5 ki ngdoms
Proka ryota
Mone ra
Mone ra
Animalia
Plantae
Animalia
Euka ryota
Woese e t al.
1990 [8]
3 domai ns
Eubacte ria
Bacte ria
Archaea
Protista
Archaebacte ria
Protista
Fung i
Fung i
Plantae
Plantae
Plantae
Animalia
Animalia
Animalia
Protista
Vegetab ilia
Woese et al.
1977 [3]
6 ki ngdoms
Euka rya
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3 Domains - current proposal
Based on ribosomal RNA sequences
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Taxonomy
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Nomenclature: assignment of a distinctive
name to each species
A scientific name of an animal consists of two
words (binomial nomenclature)
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First word is the genus and is capitalized
Second is the species written in lower case
Scientific name should be printed in italics or
underlined if handwritten
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10-11
Homo sapiens
Homo sapiens
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Taxonomy
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Some animals are subspecies, usually
caused by Geographic locations. They are
referred to as trinomials (3 names)
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All three terms are in italics
Subspecies is also in lower case
Ex. Ensantina eschscholtzii (salamander) has
many subspecies.
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E.e. plantens, E.e. picta, E.e.croceater
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Species
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Biological Species Concept
Been refined and reworded several times
 A species is a reproductive community of
populations (reproductively isolated from
others) that occupies a specific niche in
nature.
 Ability to successfully interbreed is central
to the concept
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10-14
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Species
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Biologists use certain criteria for identifying
species
 Common
Descent
 Reproductive Community
 Member of a species must form a
reproductive community that
excludes members of other species
10-15
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Taxonomic Characters and Phylogenetic Reconstruction
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Cladogram
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Diagram illustrating hierarchy of clades (groups
of animals with common ancestry)
To construct a Phylogenetic tree
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Additional information concerning ancestors,
duration of lineages, and amount of evolutionary
change must be included (compared to
cladogram)
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A cladogram
Amphioxus is the “outgroup” because it doesn’t share any of the defining
characteristic with the other taxa. What characteristic separates Bass from
Horses?
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Taxonomic Characters and Phylogenetic Reconstruction
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Sources of Phylogenetic Information
(What do we use to identify animals??)
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Comparative Morphology
Examines shapes, sizes and development of
organisms
 Skull bones, limb bones, scales, hair and
feathers
 Living specimens and fossils are used
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10-18
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Taxonomic Characters and Phylogenetic Reconstruction
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Comparative Biochemistry
Analyzes sequences of amino acids in proteins
and nucleotides sequences in nucleic acids
 Recent studies show comparative biochemistry
can be applied to fossils
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Comparative Cytology
Examines variation in number, shape and size
of chromosomes
 Used almost exclusively on living specimens
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10-19
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Phylogenetic Tree based
On Cytology:
Comparing base
substitutions on
Cyctochrome C
(a respiratory protein).
#’ s represent number of
Mutations that occurred.
10-20
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Animal Kingdom Patterns of Organization
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Symmetry
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Asymmetrical (no central
body point/axis) ex.
sponge
Bilateral (if divided
right/left sides are mirror
image) ex. vertebrates
Radial (any plane cut
through organism makes
mirror image) ex. Sea
anemone
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Embryonic Tissue
Layers:
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Diploblastic - 2 tissues
(ectoderm and
endoderm)
Triploblastic - 3 tissue
layers (also mesoderm)
Zygote Cleavage
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Protostome - blastopore
becomes mouth
Deuterostome blastopore becomes
anus
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Major Subdivisions of the Animal Kingdom
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Traditional groupings based on embryological
and anatomical characters
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Branch (Parazoa):
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phylum Porifera,
the sponges and
phylum Placozoa
Branch (Eumetazoa): all other phyla
10-23
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Major Subdivisions of the Animal Kingdom
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Branch Eumetazoa
Grade I (Radiata): phyla Cnidaria
 Grade II (Bilateria): all other phyla
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Division A (Protostomia):
(subdivisions made by
presence of coelom in embryo)
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Division B (Deuterostomia):
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Acoelomates: phyla Platyhelminthes,
Pseudocoelomates: phyla Rotifera, Nematoda,
Eucoelomates: phyla Mollusca, Annelida,
Arthropoda, Tardigrada,
phyla Echinodermata, Chordata
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Major Subdivisions of the Animal Kingdom
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Recent molecular Phylogenetic studies have
challenged traditional classification of Bilateria
 Grade II: Bilateria
 Division A: (Protostomia):(subdivisions made by
molting/shedding)
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Division B (Deuterostomia):
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Lophotrochozoa (non-molting): phyla
platyhelminthes, Rotifera, Mollusca, Annelida,
Ecdysozoa (outer covering sheds or molts): phyla
Nematoda, Arthropoda, Tardigrada,
phyla Chordata, Echinodermata