CHAPTER 10
Classification & Phylogeny of
Animals
I.
Order in Diversity
A. History
- classify or group animals by patterns of
similarity
- Systematic Zoologists have three goals:
1. to discover all species of animals
2. to reconstruct their evolutionary history
3. to classify animals according to their
evolutionary relationships
- Taxonomy is the formal system for naming
& classifying species
- Systematics is the broader science of
classifying based on similarity, biogeog, etc
- several methods of classification were
produced from adjusting taxonomy to
accommodate evolution
B. Development of Classification (Linnaeus)
- 1st classification = Aristotle
- updated by English naturalist John Ray (late
1600’s)
- current system developed by Swedish botanist
Carolus Linnaeus (mid 1700’s)
Hierarchy of Taxa
Kingdom
Phylum
Class
Order
Family
Genus
species
(additional levels of taxa:
superclass & suborder)
Binomial Nomenclature
- Binomial name:
Genus
species
(specific epithet)
*always underline or italicize*
subspecies
(trinomials)
II.
Species
Huxley questioned “what is a species?” in 1859
Criteria:
1. common descent
2. smallest distinct grouping sharing patterns of
ancestry & descent
3. reproductive community (sexual reproducing
organisms only)
Different Species Concepts:
1. Typological Species Concept
A “type specimen” is labeled & kept in
museum to represent “standard” to compare
all others
2. Biological Species Concept
Organisms reproductively isolated
- hybridization potential
- sibling species look alike, don’t breed
- asexual organisms?
3. Evolutionary Species Concept
1940’s – single lineage of ancestordescendant populations that maintains its
identity from other lineages
(own evol. tendencies & historical fate)
4. Phylogenetic Species Concept
Monophyletic unit that recognizes the
smallest groupings that undergo evol. change
(centers on ancestry & descent)
III.
Taxonomic Characters &
Phylogenetic Recognition
A. Constructing Phylogenies
- Phylogeny
Evolutionary trees based on study of
characters that vary among species
- Utilize:
Homology - character similarity that
results from common ancestry
Vestigial traits – historical remnants that
had important function in ancestors
- Be aware of:
Convergent Evolution
Different lineages develop similar
features independently
Homoplastic
(nonhomologous)
Characters that are
similar but misrepresent
common descent
B. Reconstructing Phylogeny
- must determine ancestors & descendents
ancestral forms
derived forms (arose later)
group sharing derived – clade
Use outgroups to show relationship
- phylogenetic trees derived from information on
ancestors, duration of lineage, & amount of
change
- sources of information:
1. comparative morphology
(size, shape, development)
(living & fossils)
2. comparative biochemistry
(amino acid seq in proteins)
(nucleotide seq in DNA)
(biochemical studies of fossils)
3. comparative cytology
(variation in #, size, shape of
chromosome)
4. fossils - (duration of lineage, timeline)
5. mutation Rates
(calculate rate of change in proteins
& DNA)
IV.
Theories of Taxonomy
A. Phyletic Relationships
- relationship between taxonomic groups:
1. monophyletic
taxon includes the most recent ancestor
& all descendants
2. paraphyletic
includes most recent ancestor but not all
descendants
3. polyphyletic
taxon doesn’t include most recent
ancestor; represents at least two
separate evolutionary origins
B. Traditional Taxonomy
Recognizing & ranking taxa based on:
1. common descent
2. amount of adaptive evolutionary change
C. Phylogenetic Systematics/Cladistics
Based on:
1. common descent
2. cladograms - nested hierarchy of clades
(share derived characters)
V.
Major Divisions of Life
♦ Aristotle’s two kingdom system:
Animals & Plants
♦ 1969 RH Whittaker proposed 5-kingdoms:
Plant, Animal, Protista, Fungi, Prokaryotes
Woese, Kandler, Wheelis proposed three
monophyletic domains above kingdom level:
Domains Eucarya, Bacteria, Archae
A. Major Subdivisions of the Animal
Kingdom
♦ animal phyla have been informally grouped
based on embryological & anatomical traits
♦ Metazoa synonymous with Animal Kingdom
Traditional higher-level groupings:
Phylum
Parazoa
P. Porifera
P. Placozoa
Eumetazoa
Grade 1 (Radiata)
P. Cnidaria
P. Ctenophora
Grade 2 (Bilateria)
Division A
(Protostomia)
Acoelomates:
P. Platyhelminthes
P. Gnathostomulida
P. Nemertea
Pseudocoelomates:
P. Rotifera
P. Gastrotricha
P. Kinorhyncha
P. Nematoda
P. Nematomorpha
P. Acanthocephala
P. Entoprocta
P. Priapulida
P. Loricifera
Eucoelomates:
P. Mollusca
P. Annelida
P. Arthropoda
P. Echiurida
P. Sipunculida
P. Tardigrada
P. Pentastomida
P. Onychophora
P. Pogonophora
(Deuterostomia)
P. Phoronida
P. Ectoprocta
P. Chaetognatha
P. Brachiopoda
P. Echinodermata
P. Hemichordata
P. Chordata