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 ancestor-descendant 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.Recognizing & ranking taxa based on:

2. amount of adaptive evolutionary change

Traditional Taxonomy

1. common descent

C. P atics/Cladistics B

1. 2.

V.

Plant, Animal, Protista, Fungi, Prokaryotes

hylogenetic Systemased on:

common descent cladograms - nested hierarchy of clades (share derived characters)

Major Divisions of Life

♦ Aristotle’s two kingdom system: Animals & Plants ♦ 1969 RH Whittaker proposed 5-kingdoms:

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: (Deuterostomia) P. Mollusca P. Phoronida P. Annelida P. Ectoprocta P. Arthropoda P. Chaetognatha P. Echiurida P. Brachiopoda P. Sipunculida P. Echinodermata P. Tardigrada P. Hemichordata P. Pentastomida P. Chordata P. Onychophora P. Pogonophora