Phylogeny And Systematics: Putting Things In Order

Phylogeny and Systematics putting things in order

Definitions • Phylogeny (group origin) – The evolutionary history of a species or group of related species

• Systematics – The use of morphological (appearance), and molecular comparisons to infer evolutionary relationships

23.1

Determining Phylogeny • Organisms that share very similar morphologies or similar DNA sequences are likely to be more closely related than organisms with vastly different structures or sequences

Phylogenetic Tree

Analogy vs. Homology • A potential misconception in constructing a phylogeny – Is morphological similarity due to convergent evolution, called analogy, rather than shared ancestry, called homology

23.2

Carolus Linnaeus Developed • Taxonomy – the organization of organisms into categories based on a set of characteristics

• Binomial nomenclature – the two-part format of the scientific name of an organism (genus and species) – The genus is capitalized and both words are italicized in print 23.3

Hierarchical Classification • Linnaeus also introduced a system – For grouping species in increasingly broad categories Panthera Species pardus Panthera

Genus

Felidae

Family

Carnivora

Order Class Phylum

23.3/23.4

Kingdom Domain

Mammalia Chordata Animalia Eukarya

How is taxonomic classification different from phylogenetic systematics? Taxonomy

Does not consider evolutionary history

Phylogenetic Systematics

Groups organisms using specific characters

Determines evolutionary history

23.5

Species

Panthera

Family

– In branching phylogenetic trees called cladograms

Panthera Mephitis Canis Canis Lutra lutra pardus mephitis familiaris lupus (European (leopard) (striped skunk) (domestic dog) (wolf) otter)

Order

• Systematists depict evolutionary relationships

Genus

Linking Taxonomy and Phylogeny

Felidae

Mephitis

Lutra

Mustelidae

Carnivora

Canis

Canidae

• Each branch point – Represents the divergence of two species

Leopard

23.5

Domestic cat

Common ancestor

• “Deeper” branch points – Represent progressively greater amounts of divergence

Wolf

23.5

Leopard

Common ancestor

Domestic cat

23.5

Am ph ib

D ro so ph ila La nc el et Fi sh

65.5 251 Millions of years ago

Proterozoic

542

Paleozoic

– the use of cladograms to compare the evolutionary history of different groups – depicts the number of evolutionary changes with lines of different lengths

Mesozoic Cenozoic

Cladistics

ian Bi rd Hu m R an at M ou se

Cladistics