Phylogenetics and the Tree of Life

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Phylogenetics and the Tree of Life

• Level 1 Biological Diversity
• Jim Provan

Campbell Chapters 25 26
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Key events in the evolution of life
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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

4
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

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Hierarchical classification
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Classification and phylogeny
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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

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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

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Phylogenetic systematics
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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

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Alternative classification systems
Monera
Protista
Plantae
Fungi
Animalia
Archaea
Bacteria
Protista
Chromista
Archaezoa
Domain Eukarya (Eukaryotes)
Euglenozoa
Alveolata
Rhodophya
Stramenopila
Archaezoa
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Plants - where do they (and we) fit in?
Fungi