Transcript Phylogenetics and the Tree of Life

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