Phylogeny & the Tree of Life Chapter 26

Phylogeny & Systematics Evolutionary history of a species or group of species Determined by evidences from fossil record, homologous structures, molecular homologies Systematics: Helps us understand phylogeny (data analysis of phylogeny)

Phylogenies show evolutionary relationships 26.1

Taxonomy Grouping according to evolutionary similarities Binomial nomenclature (Linnaeus) Domains  Species Taxon (plural: taxa): named taxonomic hierarchy Ex: Panthera is the taxon at the genus level

Phylogenetic Tree Links taxonomy and phylogeny Branch points Divergence of two lineages from a common ancestor Most recent common ancestor

How to read a phylogenetic tree

Phylogenies are inferred from morphological and molecular data 26.2

Recall: Homology Analogy Similarities due to common ancestry Similarities due to convergent evolution

Morphology & DNA Physical traits and genetics are homologous in organisms with recent shared common ancestors

Molecular Systematics Uses DNA and other molecules to hypothesize evolutionary history

Shared characters are used to construct phylogenetic trees 26.3

Cladistics Science of constructing a cladogram

Cladistics Clades Groups of organisms sharing a common ancestor

Monophyletic A valid clade is monophyletic, it consists of the ancestor species and all its descendants

Paraphyletic A paraphyletic clade consists of an ancestral species and some, but not all, of the descendants

Polyphyletic A polyphyletic clade includes many species that lack a common ancestor

Species Change Over Time (Nodes)

Characteristics Shared primitive character Homologous structure that is older than the branching of a particular clade from other members of that clade It is shared by more than just the taxon we are trying to define. Example – mammals all have a backbone, but so do other vertebrates.

Characteristics Shared derived character New evolutionary feature, unique to a particular group Example - all mammals have hair, and no other animals have hair.

Ingroup & Outgroup In: Group of study (make comparisons) Out: Group that diverged prior to ingroup

New information continues to revise our understanding of the tree of life 26.6

A Changing Approach to Classification of Life New evidence means continued revision of classification Genome (DNA) sequencing

Tree of Life Current classification: Three domains 6 kingdoms

3 Domains First life on Earth

Tree of Life Video