Lecture 22 - Phylogeny and Tree of Life

Biolo 1551

Processes: natural selection and other mechanisms that change genetic composition of populations

Patterns: Processes lead to evolutionary patterns - the taxa produced over time

Evolutionary Biology has two main pathways…

Phylogeny

Evolutionary history of a species or group of species

Systematics

Analytical approach to classifying the diversity and determining the evolutionary relationship of living and extinct organisms

From fossil records and from morphological, biochemical, and genetic similarites between organisms

Evidence used to reconstruct phylogenies…

Taxonomy with Linnaean system… each species has latin binomial

Used to determine how organisms are named and classified….

1st part: genus (closes group a species belongs to)

2nd part: specific epithet… single unique species within each genus

Note: First name capitalized, and italicized

Linnaean System for naming species

Hierarchical Classification

This groups species into increasingly inclusive taxonomic categories

Family, order, class, phylum, kingdom, domain

Small to biggest genera groupings

Taxon (Plural: Taxa)

Ex: Panthera is a taxon at the genus level, and Mammalia is a taxon at the class level that includes all of the many orders of mammals

Named taxonomic unit at any level…

DO NOT reflect true phylogeny

Scientist attempting to link classification and phylogeny… historical linnaean taxonomic groups…

Evolutionary relationships

Phylogenies show what?

Genes, metabolic pathways, and structural pathways with close relatives…

Organisms share homologous characteristics like?

Phylogenetic tree

Evolutionary history of a group of organisms…

Goal: Show pattern of descent, not phenotypic similarity

Does not show timing

1. identified two closely related species of wild grasses to corn with beneficial alleles that may be transferred to corn by genetic engineering/plant breeding

2. Played a role in demonstrating that “whale meat” was being harvested illegally

Species’ phylogeny can provide useful information, like… (2)

Morphological and molecular data

Phylogenies are inferred by…

Homologies

Phenotype and genetic similarities due to shared ancestry is called…

Ex: Hawaiin silversword plants… tall to shrubby… phenotypic differences based on small molecular divergence

Morphological divergence between closely related species can be small or great… may be controlled by relatively few genetic differences

Analogy

Similarity due to convergent evolution… two organisms from different lineages experience similar environmental pressure, thus Natural selection results in similar structures/traits

Molecular Systematics

Uses DNA and other molecular data to determine evolutionary relatedness Cl

Cladistics

Approach to systematics that common descent is the primary criteria used to classify the organism is called…

Clades

Clades are nested within larger clades…

Groupings of species, include ancestral species and all descendants

Monophyletic

Valid clade with ancestral species and ALL its descendants

Paraphyletic

Grouping that has some, but not all descendants with ancestor

Polyphyletic

Several groupings that include taxa with different ancestor — further research to identify groupings into monophyletic clade

Descent with Modification

Organisms share some, but not all, characteristics with thier ancestors

Character

Any feature that a particular taxon has

Shared derived character

Evolutionary novelty unique to a particular cladeS

Shared ancestral character

Originated from an ancestor of the clade

Shared Derived Characters useful for inferring phylogenies

Shared ancestral characters are not useful for creating phylogenies… what is?

Genome

Organism’s evolutionary history documented in its…

Bacteria, Archaea, Eukarya

Three Domains

Diverse group of prokaryotes — differ from bacteria in key structural, biochemical and physiological traits

Archaea

Most prokaryotes and bacteria

Bacteria

More closely related to each other than either to bacteria

Relationship between archaea, eukaryotes, and bacteria…

Horizontal Gene transfer

1. Transposable elements

2. Plasmid exchange

3. viral infection

genes are transferred from one genome to other by mechanisms like… name + (3)

Hybrid Organisms

Different organisms fused to produce new

80% of genes in 181 prokaryotic genomes moved between species at some point in evolution

Important analysis of horizontal gene transfer