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Phylogenetics
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Uploaded: 4 years ago
Category: Biology
Type: Lecture Notes
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Filename: Phylogenetics.ppt
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Transcript
Phylogeny and the Tree of Life
Systematics
Taxonomy
(classification)
Phylogenetics
(evolutionary history)
Systematics: classifying organisms and determining their evolutionary relationships
Tools used to determine evolutionary relationships:
Fossils
Morphology (homologous structures)
Molecular evidence (DNA, amino acids)
Animals and fungi are more closely related than either is to plants.
Who is more closely related?
Taxonomy: science of classifying and naming organisms
Binomial nomenclature (Genus species)
Naming system developed by Carolus Linnaeus.
REMEMBER!!
Dear King Philip Came Over For Good Spaghetti
Dear King Philip Crossed Over Five Great Seas
Dear King Philip Came Over From Germany Stoned
Your own???
Phylogenetic Tree
Branching diagram that shows evolutionary history of a group of organisms
The topology is the branching structure of the tree.
Tips represent groups of descendent taxa known as the tips or external nodes.
Internal nodes occur at the points where more than one branch meet and represent the (usually inferred) ancestral sequences.
Root is a very important internal node representing the most recent common ancestor of all sequences in the phylogeny.
Clade = group of species that includes an ancestral species + all descendents
Shared derived characteristics
an evolutionary novelty unique to a clade.
Shared ancestral characteristics
a character that originated
in an ancestor of the taxon.
Turtle
Leopard
Hair
Amniotic egg
Four walking legs
Hinged jaws
Vertebral column
Salamander
Tuna
Lamprey
Lancelet (outgroup)
Cladogram
NESTED CLADES
University of California Museum of Paleontology's Understanding Evolution
Monophyletic (from the Greek, meaning “single tribe”)
consists of an ancestral species and all of its descendants
Paraphyletic (“beside the tribe”)
consists of an ancestral species and some, but not all, of its descendants
Polyphyletic (“many tribes”)
includes distantly related species but does not include their most recent common ancestor
Monophyletic, paraphyletic, and polyphyletic groups
Constructing a phylogenetic tree
A 0 indicates a character is absent; a 1 indicates that a character is present.
An outgroup is a species or group of species from an evolutionary lineage that is closely related to but not part of the group of species that we are studying (the ingroup)
Branch lengths can represent genetic change
Branch lengths can indicate time
Draw a phylogenetic tree based on the data below. Draw hatch marks on the tree to indicate the origin(s) of each of the 6 characters.
Answer:
Interpreting patterns of relatedness
Unrooted tree
Circular (rooted) tree
Rooted tree
Various tree layouts
Principle of maximum parsimony: use simplest explanation (fewest DNA changes) for tree – “keep it simple”
Molecular clocks: some regions of DNA appear to evolve at constant rates
Estimate date of past evolutionary events
Maximum Parsimony (MP)
choose tree that minimizes number of changes required to explain data
Maximum Likelihood (ML)
under a model of sequence evolution, find the tree which gives the highest likelihood of the observed data
Tree of Life
3 Domains: Bacteria, Archaea, Eukarya
SYSTEMATICS
Biological diversity
taxonomy
Identification of species
binomial
Genus, species
D
K
P
C
O
F
G
S
phylogeny
classification
cladistics
Homologous
similarities
fossils
molecular
morphology
focuses on
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