Download Phylogenetic Trees

Phylogenetic Trees
Phylogenetic Trees and Cladograms
• What are they?
• Graphical representations (models) of
evolutionary history
▫ They show how species of the past are related to
other species
▫ Show relations that can be tested
• What does phylogeny mean?
▫ Phylogeny: Tracing the origin of a species based
on evolutionary relationships
Geology and the fossil record
• Fossils help us
produce
phylogenetic
trees based on
morphological
characteristics
Classification of living things
• Classical taxonomy was
invented by Carolus
Linnaeus
▫ All classification done by
physical characteristics
▫ Linnaeus invented
binomial nomenclature
Two names that describe a
species
Homo sapiens
Drosophila melanogaster
Canis familiarus
Mus musculus
Linnaeus
• He also created hierarchical
groups of classification
• Grouping organisms that seem to
be related by physical
characteristics
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Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Phylogenetic trees help us classify
living things
• Modern classification involves using phylogentic trees
▫ Based on evidence from
Genetics
Morphology
Development
Biochemistry
Fossils (reveal traits that have been lost)
• The goal is to find how species are evolutionarily related
▫ More in common = less likely they evolved independently
Classification and phylogeny are
linked!
• Why does classical
taxonomy overlap
with today’s
phylogenetic trees?
• Because animals that
are evolutionarily
related share physical
characteristics
Stop Here!
• Bring your questions for class tomorrow!
Phylogenetic trees and cladograms
• A cladogram is like a phylogenetic tree
• Both show that the relatedness of any two
groups by how recently the groups have had
shared a common ancestor
• How are they different?
▫ Phylogenetics is the general idea of making trees
that show evolutionary relationships
▫ Cladistics creates cladograms based on shared
derived characteristics
Phylogenetic trees and cladograms
• What is a shared derived
characteristic?
▫ A trait that every
individual has as you
move forward in the
diagram
Claws and nails are
shared derived
characteristics in this
example for lizard,
pigeon, mouse and chimp
• Example of a
phylogeny
• Made with
computer
DNA
sequencing
• Show
evolutionary
relationships
• Example of a cladogram
▫ Shows shared derived characteristics
Clade: ancestral species and all of its descendants
Making a phylogenetic tree
• Based on evidence from
▫ Genetics, Morphology, Development, Biochemistry, Fossils etc.
▫ Systematics: the process of analyzing this data to understand
species diversity and relationships
DNA is particularly helpful
• Morphological and molecular
▫ Homology vs. analogy
▫ Divergent vs. convergent
• Molecular homologies
▫ DNA sequences
▫ Proteins
▫ What challenges can be anticipated with these molecules?
Making a cladogram
• Look for homologous
characteristics
▫ Physical or Molecular
DNA, Proteins
• Shared primitive
characters – common to
all members of the group
▫ Backbone
• Shared derived characters
– found only in group of
interest
▫ Mammals and hair
Be careful!
• These things can make it seem like you have a
relationship but they can be misleading
• Morphological homologies
▫ Homology vs. analogy
▫ Divergent vs. convergent
• Molecular homologies
▫ DNA sequences
▫ Proteins
Outgroup
• Species that is less
closely related to
the entire group,
than any of the
individual
member are to the
to other members
of the group
Practice Time
• Construct a cladogram using 4 animals that you
know yourself
• Include shared derived characteristics and one
primitive characteristic
Practice time
• Make a cladogram with the following animals:
• Identify the shared derived characteristics as well as
one shared primitive characteristic
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Rabbit
Shark
Bird
Alligator
Chimpanzee
Frog
Trout
One of many possible answers
One more
• Make a cladogram with the following animals:
• Identify the shared derived characteristics as
well as one shared primitive characteristic
• Identify the outgroup
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Rat
Raccoon
Guinea Pig
Beaver
Mouse
Rabbit
28. (A) Based on the data in the table below, draw a
phylogenetic tree that reflects the evolutionary relationships of
the organisms based on the differences in their cytochrome c
amino-acid sequences. Based on the data, identify which
organism is most closely related to the chicken and explain
your choice.
THE NUMBER OF AMINO ACID DIFFERENCES IN CYTOCHROME c
AMONG VARIOUS ORGANISMS
Horse
Horse
Donkey
Chicken
Penguin
Snake
Donkey Chicken Penguin Snake
0
1
11
13
21
0
10
12
20
0
3
18
0
17
0
Cladograms and phylogenetic trees are
a work in progress
• Constantly being revised based on new data
• Scientists like to fight