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Classification & Phylogeny General Zoology LS2014 Donald Winslow 31 January 2011 Hickman, Cleveland P., Jr.; Larry S. Roberts; Susan L. Keen; David J.

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Presentation on theme: "Classification & Phylogeny General Zoology LS2014 Donald Winslow 31 January 2011 Hickman, Cleveland P., Jr.; Larry S. Roberts; Susan L. Keen; David J."— Presentation transcript:

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, 15 th 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 1 st 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, 15 th 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 taxons sister taxon is the one that shares the most recent common ancestor.

16 Species concepts Basic criteria –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


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