Transcript cladisticsAP - Needham.K12.ma.us

Organizing
Biodiversity with
Evolutionary Trees
Classification & Taxonomy
• Aristotle - first classification system
• John Ray - developed classification
system and a new concept of species
• Carolus Linnaeus - system of hierarchical
classification and binomial nomenclature
What is Systematics?
• Systematics is the branch of Biology
that seeks to classify biodiversity using
everything known about an organism in
order to understand its evolutionary
relationship to other organisms.
Early Classification vs. Modern Analysis
Pre- Darwinian
Post-Darwinian
Organisms are
grouped
according to
similar
physical
characteristics
Organisms are
grouped
according to
evolutionary
relationships
Dichotomous Keys vs.
Phylogentic Trees
• How is the purpose of each of these
diagrams different?
• How is the structure different?
Tree of Life
• All organisms are related, but some are
more closely related than others.
• To represent the idea that all living things,
despite their diversity, share a common
ancestor, Darwin used the metaphor of a
“tree of life”.
Tree Thinking
“The affinities of all the beings of the same class
have sometimes been represented by a great
tree…The green and budding twigs may
represent existing species; and those produced
during each former year may represent the long
succession of extinct species… As buds give rise
by growth to fresh buds, and these, if vigorous,
branch out and overtop on all sides many a
feebler branch, so by generation I believe it has
been with the great Tree of Life.”
Charles Darwin, On the Origins of Species (1859)
This “tree”
illustration
was the
only one
included in
Darwin’s
Origin of
Species.
Darwin’s Tree
Image taken from http://www.mala.bc.ca/~johnstoi/darwin/origin_abridged.htm
The Tree of Life Project
• The Tree of Life Web
Project (ToL) is a
collaborative effort
of biologists from
around the world.
The project seeks to
create a “super
tree” which
organizes the
diversity of
organisms on Earth
through their
evolutionary history.
Creating Evolutionary Trees
• Comparative studies and fossils may be used
to create initial phylogentic hypotheses
• Molecular techniques may be used to test or
refine initial hypotheses
• Computer programs are readily available to
analyze vast amounts of phylogenetic data
Based on the following
character table, draw a tree
Cladograms and Phylogenetic Trees
How to read a cladogram
• Lines represent
history through time.
• Nodes represent
ancestors that are
extinct, but common
to organisms
Clade-istics
• Clade--group of
organisms that
share their most
recent common
ancestor
Evolutionary trees are
hypotheses!
• Different sources of evidence may lead to
the development of competing trees
• The principle of parsimony (choosing the
least complex hypothesis) guides
systematists in their reconstruction of trees
What is Cladistics?
• A method of analyzing evolutionary
relationships between groups to construct
a cladogram or “family tree”
• The branching tips of a cladogram must
represent a clade, an ancestral species
and ALL its descendents.
Clades
No more
Reptiles??
http://www.enchantedlearning.com/subjects/reptiles/printouts.shtml
Using cladistics, the traditional reptile grouping
does not include ALL descendents
Methods
Cladistic analysis involves comparing
similarities (homologies) between
organisms in order to determine
primitive vs. derived characteristics.
• Primitive - characteristics that all members of a
group share
• Derived - modified characteristics that only
some members share
Fossils
Morphology
Behavior
Physiology
Data Sources
Geography
Geology
Molecular Evidence
Ecology
Reading
• Read “Tree
Thinking Challenge”
– Which tree is more
accurate?
– What is the basis for
trees?
– What do nodes
represent?
Practice
• Try the “odds”
today and the
“evens” for
homework.
• You will get an
answer key on
Wednesday!
• They get harder as
you go on!
Today’s Activity
Birdwing Butterflies: We will use a combination of geographic,
physical, and genetic evidence to determine the evolutionary
history of birdwing butterflies.
More Activities Later in the
Year
• HIV Evolution: We
will use a computer
program to compare
HIV virus and
determine the
evolutionary origin.
Tools
• Available Software for Phylogenetic Analysis
PAUP
Hennig86
MacClade
http:/onyx.si.edu/PAUP
http://www.vims.edu/`mes/hennig/software.html
http://phylogeny.arizona.edu/macclade/macclade.htm
• Molecular Data Bases on the Web
Genbank http://www.ncbi.nim.nih.gov/Entrez
Protein Information Resource (PIR)
http://pir.georgetown.edu
Resources
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“A Science Primer: Classification and Phylogenetics” http://www.ncbi.nih.gov/About/primer/phylo.html
Baum, D.A.,et al. “ The Tree Thinking Challenge” Science 310:979-980.
Campbell, N.A. and Reece, J. B. Biology 6th edition. San Francisco: Benjamin Cummings, 2002.
Clos, L.M. “What is Cladistics?” [6/8/06] http://www.fossilnews.com/1996/cladistics.htm
Filson, R. “Island Biogeography and Evolution: Solving a Phylogenetic Puzzle with Molecular Genetics”
http://www.accessexcellence.org/AE/AEPC/WWC/1995/simulation_island.html
Kramer, B. and Flammer, L. “Making Cladograms: Phylogeny, Evolution, and Comparative Anatomy”
Evolution & Nature of Science Institutes (ENSI/SENSI), University of Indiana. [6/8/06]
http://www.indiana.edu/~ensiweb/lessons/mclad.html
“Names & classifying living things” http://www.backyardnature.net/names.htm
Singer, F., et al “The Comparative Method, Hypothesis Testing & Phylogentic Analysis” The American
Biology Teacher 63(7): 518-523.
Skelton, P. W., A. Smith, et al. (2002). Cladistics a practical primer on CD-ROM. Cambridge, The Open
University; Cambridge University Press.
“The Tree of Life Web Project’ http://www.tolweb.org/tree/
“Tree-thinking Group” http://www.tree-thinking.org
“Understanding Evolution: An Evolution Web Site for Teachers” http://evolution.berkeley.edu/
“What did Trex taste like? An introduction to how life is related”
http://www.ucmp.berkeley.edu/education/explorations/tours/Trex/guide/index.html