Chapter 2 Systematics and Vertebrate Evolution
Introduction
Classification:
(1) grouping together of related forms: Systematics
(2) application of names to the groups: Taxonomy
Species are the fundamental units of systematics and are the basis of classification.
The classification of organisms is based primarily on the presence of similarities and the differences among groups of living organisms.
Fossils are used whenever possible to extend lineages back into geologic time and to clarify the evolution of groups.
Binomial nomenclature二名法
Carolus Linnaeus (1707-1778):
1758 Systema Naturae: the binomial system of nomenclature (two names)
scientific names:
genus name + trivial name
common name Fig.2.1 puma=mountain lion=panther Puma concolor (Linnaeus)
Classification
Morphological species concept
Biological species concept (Mayr 1969)
Taxonomic categories
Kingdom-Animalia
Phylum-Chordata
Class-Mammalia哺乳綱
Order-Carnivora食肉目
Family-Felidae貓科
Genus-Puma
Species-Puma concolor
1958 International Code of Zoological Nomerclature
Methods of Classification
Taxon is a taxonomic group
The relationship of taxa:
Monophyletic Fig.2.2a
Paraphyletic Fig.2.2b
Polyphyletic Fig.2.2c
Methods:
1. Aristotelean essentialism: Aristotle 384-322B.C.
Based on the degree of similarity of shared ‘essential’ traits
2. Evolutionary (Classical or Traditional) Classification
Similarities in structure are evidence of evolutionary relationships
Subjectivity
3. Phenetic (Numerical) Classification
Overall similarity (phenotypic characters)
Computer groups the organisms into Clusters based on similarity
Phenogram: phenon
Expanded in the early 1960s
Molecular taxonomy
4. Cladistic (Phylogenetic) Classification
1950, common descent based on the cladogram of the group being classified, focuses on shared, derived characters
reflect organisms’ evolutionary histories
monophyletic taxa
synapomorphics: shared derived characters
plesiomorphics: primitive traits inherited from an ancestor
symplesimorphics:
Cladeogram: clades Fig. 2.3, 2.4
Outgroup comparison
Sister group
Fig. 2.5 Comparison of evolutionary and cladistic systematics among the amniotes
Fig. 2.6 Classifications based strictly on cladistics would require numerous taxonomic levels and be too complex for convenience.
Fig.2.7 Some cladistic classifications require compromises.
Fig. 2.8 Construction of a cladogram
Evolution
Evolution is the underlying principle of biology
Natural selection
The change in the genetic makeup of a population over successive generation is evolution
1. Species and speciation
Deme: a small local population
Cline: Fig.2.9
Species: gene flow
Subspecies
Speciation:
Primary isolation barrier
Allopatric populations: geographic isolation
Secondaty isolation barriers Fig.2.10 Mechaism prohibit interbreeding
Pre-mating (prezygotic) barrier
Ecological
Ethological
Morphological
Post-mating (postzygotic)
Physiological
Cytological
Allopatric speciation Fig 2.11a,b
Founder effect
Sympatric speciation Fig.2.11c
Fig.2.12 the cichlid of Africa
Fig.2.13related cichlids from Lakes Tanganyika and Malawi
2. Geographic Variation
(1)Bergmann’s Rules
(2)Allen’s Rule Fig. 2.14
(3)Glogeri’s Rule Fig.2.14
3.Molecular Evolution
mt DNA, RNA, isozyme, and the amino acid sequences of proteins such as hemoglobin and cytochrome c – are being analyzed
Fig. 2.15
DNA fingerprinting
DNA hybridization Fig. 2.18