Download Phylogeny

Phylogeny &
Systematics
Chapter 15
What you need to know!
The taxonomic categories and how they
indicate relatedness.
 How systematics is used to develop
phylogenetic trees.
 The three domains of life including their
similarities and their differences.

Phylogeny
Phylogeny – evolutionary history of a
species or group of species
 Sources of evidence:
1. Fossil Record
2. Systematics – classifying organisms
and evolutionary relatedness

A. Morphological homology
B. Molecular homology
Systematics
A.
Morphological Homology
– similarities due to shared ancestry
(homologous structures)
– determined by how two organisms appear
• Analogous structures can be misleading
(convergent evolution NOT relatedness)
B.
Molecular Homology
– Similarities in the DNA base sequences
– Most accurate
– 20 billion + base pairs sequenced so far
(1,000’s of species) – BLAST Lab
Taxonomy
Carolus Linnaeus (1701-1778)
 Mostly morphological (grouping,
separating organism due to body plans)
 Latin based binomial nomenclature:
 Each species is ID’d by genus (capital
letter) and species (lower case)

– Canis familiaris, Canis lupus, Felix catus,
Homo Sapien
All organisms classified in a
hierarchy
Taxon
Domain (broad)
Kingdom
Phylum
Class
Order
Family
Genus
Species (specific)
Memory
Did
King
Philip
Come
Over
From
Germany
Singing
Wolf
Eukarya
Animalia
Chordata
Mammalia
Carnivora
Canidae
Canis
Lupus
Phylogenetic Trees
Cladistics
Organizing organisms into clades
according to their phylogenetic
(evolutionary) relationship
 Using comparative morphology
(taxonomy), and DNA analysis
 Ancestral species placed on the bottom,
with new features leading to novel
descendants
 Ingroups are the focus organisms,
outgroups are close relatives

Cladogram
Molecular Systematics
Comparing nucleic acids and DNA for
relatedness (most accurate)
 Examples:

– DNA Comparisons
– Molecular Clocks: rate of genetic change
• Nuclear DNA slower than mitochondrial DNA
– Genome Evolution: Compare organisms
entire genetic code (humans vs. chimps
99%)
Domains – Universal Tree of Life