Systematics

The study of biological

diversity in an

evolutionary context

Systematic Tools

Molecular Comparisons– usually (rRNA or

mtDNA) DNA-DNA

Hybridization Restriction maps DNA Sequence

analysis

Taxonomy

The science concerned with naming and classifying the diverse forms of life

Taxonomic GroupsDomain

Kingdom

Phylum (Division)

Class

Order

Family

Genus

Species

Domains (Table 27.2)

Bacteria Archaea EukaryaCell type Prokaryote Prokaryote Eukaryote

Introns Absent Present Present

RNA Poly One Several Several

P. S. Formyl-methionine

Methionine Methionine

Binomial Nomenclature

Panthera leo

(African Lion)

Binomial Nomenclature

Ardea herodias

(Great Blue Heron)

Classification and Phylogeny

Phylogenetic Groupings Monophyletic

– ancestor and all its descendants

Phylogenetic Groupings Paraphyletic

– ancestor with some but not all its descendants

Phylogenetic Groupings Polyphyletic

– two different ancestors

Phylogenetic Groupings

Similarities

Homology– likeness attributed

to shared ancestry

Similarities

Analogy– likeness due to

similar ecological roles and natural selection due to convergent evolution

Molecular Homoplasy

Analogous species that have similar DNA sequences that evolved independently in two species

Ontogeny Recapitulates Phylogeny (Ernst Haeckel)

Ontogeny – individual development

Recapitulates – repeats

Phylogeny – evolutionary descent

The Science of Systematics

Phenetics

– based on a number of similarities and differences

– does not take into account homology or analogy

– all groupings

Classical Evolutionary Systematics

George Gaylord Simpson

The Science of Phylogenetic Systematics

Classical Evolutionary Systematics

– most commonly used up until recently

– based on shared homologous structures

– takes into account the amount of adaptive evolutionary change (novelties)

– Monophyletic and paraphyletic groupings

The Science of Systematics

Cladistics (Phylogenetic Systematics)– based on shared

homologous structures

– only monophyletic groupings

Will Hennig

The Science of Phylogenetic Systematics

Cladistic Assumptions

1. Monophyletic

2. Descent follows a bifurcating pattern

3. Changes in characteristics occur in lineages over time

Cladistics

Shared primitive characters

– Outgroupings

– Plesiomorphies Ancestral

characteristics Shared derived characters

– Synapomorphies

Phylograms

Ultrametric Trees

Cladistics

Cladistics

Cladistics

Pitfalls

Reptiles?????

Molecular Clock

Tree of Life

Phylogenetic Fuse