Ch 20: Phylogenies

All of life related through a…

Common ancestor

Phylogeny

evolutionary history of relationships between organisms

Phylogenetic tree

diagrammatic reconstruction of the evolutionary history of species, populations, & genes

Systematics

study of classification of biodiversity

evolutionary relationships (tree of life) form basis of…

biological classification

Horizontal gene transfer

complication of phylogeny… things dont just branch off thru natural selection, actual genes cross domain lines

Phylogenetic trees are constructed based on…

physical structures, phenotypes, behaviors

What allows biolofgsts to reconstruct history of life in more detail?

genome sequencing

Taxon

any group of species we designate or name

• amniotes, mammals

Clade

a taxon that consists of all the descendants of a common ancestor

Every species has two names

genus (name it belongs to) —> capital letter

species name

Families - suffixes

-diae for animals

-aceae for plants

Why use latin?

• confusion in using different languages for names

• Language of scholars

• Dead language

what is the branching point in a phylogenetic tree called?

Node - represents a point at which lines diverge

What does the red dot represent in phylogenetic trees?

derived traits

Ancestral trait

trait present in ancestor

Outgroup

closely related but not member of '“focus” group

Derived trait

trait in a descendant that differs from ancestral trait

Sister species

2 species that are each others closest relatives

Sister clades

2 clades that are each others closest relatives

Homologous structure

same evolutionary origin

• Shared by 2 or more species that were inherited from a common ancestor

• descent with modification

Analogous structures

independent origins

• Similarity due to similar ecological pressures

• Same type of trait adaptive in given environment

Convergent evolution

independently evolved traits subjected to similar selection pressures may become superficially similar 

Synapomorphies

are derived traits shared among a group

• evidence of common ancestry

Notochord

the ancestral trait was an undivided supporting rod

Evolutionary reversal

reverting from a derived state back to ancestral state 

Homoplasies

Similar traits generated by convergent evolution and evolutionary reversals

Ingroup

group of primary interest

Ingroup compared with…

an outgroup (a closely related species or group outside group of interest)

Parsimony principle

simplest explanation of data is preferred

Occam’s razor

best explanation is the one that best fits data with fewest assumptions

Molecular clock hypothesis

rates of molecular change are constant enough to predict timing of evolutionary divergence

 Molecular clock

average rate at which a gene or protein accumulates changes

Monophyletic

a taxon contains an ancestor and all descendants of that ancestor & no other organisms 

• taxa should be monophyletic

Polyphyletic

a group that does not include its common ancestor

Paraphyletic

a group that does not include all descendants of a common ancestor