Phylogenetics and the Tree of Life Level 1 Biological Diversity Jim Provan Campbell: Chapters 25 & 26

Key events in the evolution of life

The major lineages of life Linnaeus originally divided all known forms of life between animal and plant kingdoms The discovery of bacteria did not change this: Bacteria classed with plants Fungi classed with plants Unicellular creatures: –Ingest food: animals (protozoa) –Photosynthetic: plants

Taxonomy employs a hierarchical system of classification Developed by Linnaeus Has two main features: Binomial (latin name) unique to each species –First word is genus; second word is specific epithet –Each genus can include many related species –Defines organism and removes ambiguity A hierarchical “filing system”: –Begins with binomial nomenclature –Progresses upwards, becoming more inclusive –Range of taxonomic levels

Hierarchical classification DomainEukarya

Classification and phylogeny

Determining monophyletic taxa In order to truly reflect evolutionary history, all taxonomic levels should be monophyletic Not always the case: Kingdom Plantae is polyphyletic Class Reptilia is paraphyletic, since it does not include Aves

Discriminating between homology and analogy Homology: likeness due to shared ancestry Analogy: likeness due to convergent evolution: Forelimbs of mammals are homologous Wings of birds and bats are analogous since they originated independently from forelimbs of different ancestors

Phylogenetic systematics

The traditional five-kingdom system Proposed by Robert Whittaker in 1969 Recognises prokaryotes and eukaryotes All prokaryotes placed in Kingdom Monera Recognises three kingdoms of multicellular eukaryotes Protists are largely unicellular eukaryotes

Domain Eukarya (Eukaryotes) Alternative classification systems Monera Protista Plantae Fungi Animalia Plantae Fungi Animalia Chromista Protista Archaezoa Archaea Bacteria Plantae Fungi Animalia Rhodophya Stramenopila Archaezoa Domain Archaea Domain Archaea Domain Bacteria Domain Bacteria Euglenozoa Alveolata

Plants - where do they (and we) fit in? BacteriaArchaea Eukarya AnimalsFungiPlants