phylogeny

12
Phylogeny Phylogeny (Greek: phylon (tribe) and genesis (birth)) = classification of organisms using “trees” to order ancestors → descendants Taxonomy = practice of identifying & categorizing organisms o classification scheme o historically based on morphological features o not necessarily an evolutionary implication iogenesii.files.wordpress.com/.../image016.jpg

Upload: jubal

Post on 03-Feb-2016

36 views

Category:

Documents


0 download

DESCRIPTION

Phylogeny. Phylogeny (Greek: phylon (tribe) and genesis (birth)) = classification of organisms using “trees” to order ancestors → descendants Taxonomy = practice of identifying & categorizing organisms classification scheme historically based on morphological features - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: Phylogeny

Phylogeny Phylogeny (Greek: phylon (tribe) and genesis (birth)) =

classification of organisms using “trees” to order ancestors → descendants

Taxonomy = practice of identifying

& categorizing organisms o classification schemeo historically based on

morphological featureso not necessarily an

evolutionary implication

www.diogenesii.files.wordpress.com/.../image016.jpg

Page 2: Phylogeny

Systematics = scientific study of biological diversity in an evolutionary contexto includes: morphological, molecular genetic, biochemical, physiological,

ecological traitso CLADISTICS is a form of biological systematics that classifies

organisms into hierarchical monophyletic groups. For statistical hypothesis testing → SIMPLEST TREE- size of clades will vary- more characters will “strengthen” the tree

ancient modern

Graham et al. 2009

Page 3: Phylogeny

Monophyletic group is a taxon (group of organismsorganisms) which forms a clade, meaning that it consists of an ancestor and all its descendants.

Monophyletic group is a taxon (group of organismsorganisms) which forms a clade, meaning that it consists of an ancestor and all its descendants.

Monophyletic groupMonophyletic group

Page 4: Phylogeny

Derived Characters

primitive and derived are relativeand only have meaning when placed in context shared, derived characters = synapomorphies a derived character in one group might be primitive in another e.g., fur among tetrapods (4-footed vertebrates) = derived, but…

fur among mammals = primitive

Page 5: Phylogeny

Shared derived characters

Character: any feature exhibited by a taxon Homologous characters are used to construct cladorgrams

Shared primitive character: homology common to a more inclusive taxon Shared derived character: a unique evolutionary novelty in a clade

All similar characters

Analogous

HomologousAncestral

Derived

Example: backbone vs hair• not all animals posses hair, but all mammals –who have hair as a unique character also have a backbone, a trait shared with all other vertebrates

Page 6: Phylogeny

Constructing a Phylogeny

Select a focal group

Identify characters to be used in the analysis- ancient vs. derived

Determine the outgroup (i.e., the group that most closely resembles the ancient condition)

Construct a phylogenetic tree

Page 7: Phylogeny

ParsimonyThe simplest explanation consistent with the data.The smallest number of evolutionary changes needed to explain a phylogenetic tree (cladogram).

Sites 2-4

Sites 5-6

Site 7

Phylogenetic trees are hypothesis .

Page 8: Phylogeny

Phylogenetic trees are hypotheses

Sometimes most parsimonious tree does not reflect a true phylogeny.

There are more shared primitive characters between lizards and birds, than birds with mammals.

Page 9: Phylogeny
Page 10: Phylogeny

Remember… Ancient/primitive SIMPLE!!

A character can NOT be gained → lost → gained…

Focus on conserved cf. plastic character traits - flower color is plastic: mutates → changes readily from one

generation to the next

THINK OUTSIDE THE BOX…!!

Page 11: Phylogeny

OUTGROUP

Page 12: Phylogeny

Examples

OUTGROUP