Download Evolution, Phylogeny, and Taxonomy

Department of Geological Sciences | Indiana University
Geol G-308
Paleontology and Geology of Indiana
Bryozoa
Evolutionary relationships
1
Porifera
Phylogeny
Brachiopoda
(c) 2012, P. David Polly
1
0
0
0
P. David Polly
Department of Geological Sciences
Indiana University
Bloomington, Indiana 47405 USA
[email protected]
1
1
Department of Geological Sciences | Indiana University
(c) 2012, P. David Polly
Geol G-308
Paleontology and Geology of Indiana
Objectives
1. Basic principles of phylogenetic trees
2. Terminology of phylogenetic trees and characters
3. Evidence for phylogeny
4. Evolution, descent with modification, and natural selection
5. Phylogeny reconstruction, traits, and parsimony
6. Metazoan phylogeny
7. Field gear
Department of Geological Sciences | Indiana University
(c) 2012, P. David Polly
Geol G-308
Paleontology and Geology of Indiana
Metazoan Phylogeny
Valentine, JW, D Jablonski, DH Erwin, 1999. Fossils, molecules
and embryos: new perspectives on the Cambrian explosion.
Development, 126: 851-859.
Department of Geological Sciences | Indiana University
Geol G-308
Paleontology and Geology of Indiana
(c) 2012, P. David Polly
Phylogenetic trees show closeness of evolutionary
relationship
Evolutionary relationship is shown by
branching patterns of the tree
Taxa that share a common node
(connection) share a common ancestor
A
B
C
D
E
Relationships can be drawn as tree or
written as nested sets
Examples:
A and B are more closely related to each
other than either is to C, D, or E
C, D, and E are more closely related than
any of the three are to A and B
((A,B), (C, (D,E)))
A and B share a more recent common
ancestor with each other than either does
to C, D or E
after Page and Holmes, 1998, Molecular Evolution: a
Phylogenetic Perspective.
Department of Geological Sciences | Indiana University
Geol G-308
Paleontology and Geology of Indiana
(c) 2012, P. David Polly
Phylogenetic tree terminology
Terminal node
(leaf, tip)
Internal node
(hypothetical
ancestor)
Root
Branch
(edge)
after Page and Holmes, 1998, Molecular Evolution: a
Phylogenetic Perspective.
Department of Geological Sciences | Indiana University
Geol G-308
Paleontology and Geology of Indiana
(c) 2012, P. David Polly
Trees are like mobiles
Only the branching order matters, not the graphical
arrangement of the tree
A
B
C
D
D
=
C
B
A
B
C
D
A
=
after Page and Holmes, 1998, Molecular Evolution: a
Phylogenetic Perspective.
Department of Geological Sciences | Indiana University
(c) 2012, P. David Polly
Geol G-308
Paleontology and Geology of Indiana
Evidence for phylogeny
Phylogeny, like all scientific knowledge, is based on
inference supported by evidence. To be scientific a
phylogenetic hypothesis must be testable.
Evidence for phylogenetic relationships comes primarily
from characteristics that are shared between taxa.
Taxa can share characteristics because they share a
common ancestor, from which they inherited the shared
traits, or by convergent evolution in which they acquired
the traits independently.
Traits shared by common ancestry are the evidence for
phylogenetic relationship. Testing is done by considering
new sets of traits.
Department of Geological Sciences | Indiana University
Geol G-308
Paleontology and Geology of Indiana
(c) 2012, P. David Polly
Bryozoa
Brachiopoda
Porifera
1
1
0
1
Porifera
Porifera
0
Brachiopoda
Brachiopoda
1
1
Bryozoa
Bryozoa
Homology or synapomorphy
1
0
1
0
1
0
0 = no lophophore
1 = presence of lophophore
Homology is a characteristic shared by two or more taxa that they inherited from a
common ancestor. In phylogenetic analysis, a homologous trait is called a
synapomorphy (syn=shared, apo=derived, morphy=characteristic)
The lophophore of bryozoans and brachiopods is homologous. As a synapomorphy, it
provides evidence that the two groups are closely related.
after Page and Holmes, 1998, Molecular Evolution: a
Phylogenetic Perspective.
Department of Geological Sciences | Indiana University
Geol G-308
Paleontology and Geology of Indiana
(c) 2012, P. David Polly
Character terminology
Apomorphies are characters that evolved
since the root of the tree. Also known as
derived characters. Calcareous skeletons are
apomorphies within metazoans.
Apomorphies
Plesiomorphies
Synapomorphy
= homology
Plesiomorphies are characters present in
the ancestor at the root of the tree. Also
known as ancestral or primitive characters.
DNA and cell nuclei are pleisiomorphies for all metazoans
Synapomorphy is an apomorphic character
that is shared by more than one taxon.
Synapomorphies provide evidence for close
relationship. Lophophores are synapomorphies of
Autapomorphy
Homoplasy
=convergent evolution
brachiopods and bryozoans.
Autapomorphy is an apomorphic character
found in only one taxon. The notocord
Homoplasies are apomorphic characters
that evolved on separate branches and are
not inherited from a common ancestry.
Calcareous skeletons are homoplasies within metazoans.
after Page and Holmes, 1998, Molecular Evolution: a
Phylogenetic Perspective.
Department of Geological Sciences | Indiana University
(c) 2012, P. David Polly
Geol G-308
Paleontology and Geology of Indiana
Darwin and the theory of natural selection
A very conservative man, related to the Wedgwoods
Traveled around the world as naturalist and captain’s companion on The
Beagle, a British navy ship, in the 1830s. (Richard Owen described fossils
collected by Darwin in South America. Visited Galapagos Islands.
Determined how coral atolls are formed.)
Published On the Origin of Species in 1859, explaining the concept of
natural selection and outlining the evidence supporting it.
Darwin’s work:
• Explained homology as the similarity due to genetic relationship and
specialization as difference due to adaptation.
• Provided a scientific mechanism for how evolution works.
• Explained that extinction could happen through failure to adapt to
changing environments.
Department of Geological Sciences | Indiana University
(c) 2012, P. David Polly
Natural selection as mechanism for evolution
1. Among individuals within every species there exists considerable
variation.
2. Variable features found in parents are passed on to their
offspring.
3. Every species produces more young than survive into the
subsequent generation, therefore, competition for survival exists
within species.
4. If one’s individual characteristics give an advantage in the
competition, then that individual is more likely to survive into the
next generation.
5. The characteristics possessed by the disadvantaged individuals
are not passed into subsequent generations, but the
characteristics of the advantaged ones are.
Geol G-308
Paleontology and Geology of Indiana
Department of Geological Sciences | Indiana University
(c) 2012, P. David Polly
Descent with modification
Homologous structures are passed from each
generation to the next, but natural selection
filters variation at every step.
Species become adapted to their environment
because of the natural selection process.
As environments change over geological time,
natural selection continues to change species
in response.
When change is too rapid for adaptation to
occur or when natural variation doesn’t include
fit varieties, the species becomes extinct.
Geol G-308
Paleontology and Geology of Indiana
Department of Geological Sciences | Indiana University
Geol G-308
Paleontology and Geology of Indiana
(c) 2012, P. David Polly
Phylogenetic analysis
Synapomorphies are shared modified features, which indicate that
two taxa descended from the same ancestor.
Phylogenetic analysis finds the tree that maximizes the number of
synapomorphies.
0
0
1
0
0
1
0
1
1
1
0
0 = no lophophore
1 = presence of lophophore
1
Porifera
1
Brachiopoda
1
Bryozoa
0
Hypothesis 3
Porifera
Brachiopoda
1
Bryozoa
Porifera
1
Hypothesis 2
Brachiopoda
Bryozoa
Hypothesis 1
1
0
Department of Geological Sciences | Indiana University
Geol G-308
Paleontology and Geology of Indiana
(c) 2012, P. David Polly
Phylogeny of major Paleozoic animal phyla
Bilateria
Protostomia
Chordata
Echinodermata
Mollusca
Bryozoa
Brachiopoda
Cnidaria
Porifera
Lophophorata
Ecdysozoa Deuterostomia
Arthropoda
Lophotrochozoa
•bilateral symmetry
(sometimes restricted to
early developmental stages)
•radial cleavage of early
embryonic cell divisions
•blastopore (opening in early
embryo) becomes anus
•blastopore becomes mouth
•trochozoan larva (cilia around
middle)
•lophophore
•exoskeleton that is shed
Valentine, JW, D Jablonski, DH Erwin, 1999. Fossils, molecules
and embryos: new perspectives on the Cambrian explosion.
Development, 126: 851-859.
Department of Geological Sciences | Indiana University
Geol G-308
Paleontology and Geology of Indiana
(c) 2012, P. David Polly
Field tools
Geological hammer
Waterproof pen
Handlens
Notebook
Chisels
Specimen
bags
Department of Geological Sciences | Indiana University
(c) 2012, P. David Polly
Field notes
Geol G-308
Paleontology and Geology of Indiana
Department of Geological Sciences | Indiana University
(c) 2012, P. David Polly
Field tags
Geol G-308
Paleontology and Geology of Indiana