1. Classification & Phylogeny
General Zoology LS2014
Donald Winslow
31 January 2011
Hickman, Cleveland P., Jr.; Larry S. Roberts; Susan L. Keen; David J. Eisenhour; Allan Larson, and Helen l'Anson Integrated Principles of Zoology, 15th ed., McGraw-Hill, NY. Ch. 10 pp ,

2. Approaches to classification
Taxonomy (Linnaeus)
Classified by similar characters
Phenetics
Quantitative approach based on similarity
Systematics (cladistics)
Based on phylogeny (patterns of descent)
Evolutionary taxonomy
Incorporates phylogeny and similarity

3. Taxonomic Hierarchy
Kingdom
Phylum
Class
Order
Family
Genus
Species

4. Binomial nomenclature
Scientific name of a species italicized
1st letter of genus name is capitalized
Specific epithet is all lower-case
Examples:
Homo sapiens (human)
Sciurus niger (fox squirrel)
Branta canadensis (Canada Goose)
Junco hyemalis (Dark-eyed Junco)

5. Subspecies A subset (lower-order taxon) of a species
Trinomial nomenclature
Example: Junco hyemalis mearnsi

6. Type specimens & authority
Characteristics of a species were historically defined by “type” specimens kept at museums.
The taxonomist who names a species is the authority for that species. The name of the authority is often given with the scientific name of the species.
Example: Carduus nutans Linnaeus
(musk thistle)

7. Ancestral & derived characters
A character is a morphological feature or other aspect of phenotype.
An ancestral character is one that was present in the ancestors of a taxon.
A derived character is one that appeared during the evolution of a taxon.

8. Homology and homoplasy
A homologous character is one that is similar between two taxa because of common descent.
A homoplasic (analogous) character is one that is similar between two taxa because of convergent evolution.

9. Cladistics Nested hierarchy of lineages within clades
Compared with outgroup
Synapomorphies useful to define clades
Cladogram shows only extant species.
Phylogenetic tree includes ancestors.
Parsimony used to choose cladogram.
Sources of phylogenetic information

10. Synapomorphy
Derived character
Shared by all members of a clade

11. Parsimony
The simplest explanation that is consistent with the evidence is the most likely to be correct.
Not necessarily likely to be correct!
The cladogram that assumes the fewest character transitions is the most parsimonious.
Characters may be morphological, biochemical, behavioral, cytological, etc.

12. Biochemical cladistics
Uses comparative approach
Derives phylogenies from DNA sequences
Hickman et al. Pp
Hickman, Cleveland P., Jr.; Larry S. Roberts; Susan L. Keen; David J. Eisenhour; Allan Larson, and Helen l'Anson Integrated Principles of Zoology, 15th ed., McGraw-Hill, NY.

13. Types of taxonomic classification
Monophyly
A monophyletic taxon includes the common ancestor of all members of the taxon and all descendants of that common ancestor.
Paraphyly
Includes the common ancestor and some, but not all, descendants of that common ancestor.
Polyphyly
Does not include the common ancestor.

14. Clades & grades
Examples
Penguins
Apes & humans

15. Sister taxa
A taxon’s sister taxon is the one that shares the most recent common ancestor.

16. Species concepts Basic criteria Typological species concept
Common descent
Smallest distinct groupings
Interbreeding
Typological species concept
Biological species concept
Evolutionary species concept
Phylogenetic species concept

17. Typological species concept
Fixed & essential features
Defined by type specimen

18. Biological species concept
Interbreeding population
Reproductively isolated from other populations
Does not work well for asexual species

19. Evolutionary species concept
Isolated from other populations
Distinct evolution and fate
Works for asexual species

20. Phylogenetic species concept
Irreducibly distinct from other groups
Also works for asexual taxa
Often involves splitting taxa into separate species