BIS2C
Winter 2011
Midterm 1
Study guide part I
Understanding trees, tree-based thinking, and phylogenetic applications
Basic concepts
What is a
phylogenetic tree
?
What are the basic elements of a tree (
terminal taxa
,
internal nodes
,
root node
, etc.)?
Distinguishing between
cladograms
,
phylograms
and
chronograms
.
In what way is a tree a
simplification
of a more complex evolutionary process?
How does a
monophyletic group (=clade)
differ from a non-monophyletic group (
paraphyletic
group
or
polyphyletic group
)?
What is a
synapomorphy
?
Why are monophyletic groups characterized by synapomorphies?
Explain how an attribute (character) that is an
ancestral
state
in one context can be a
derived
state
in another context.
Distinguish between
convergence
,
reversal
and
homology
.
What is the relationship between phylogeny and
classification
?
Define the following:
sister groups
,
ingroups
and
outgroups
.
Understand why branch rotation does not change meaning of the tree.
Be able to determine if
two trees are equivalent.
Reconstructing phylogenetic trees
Remember that trees are
hypotheses
. They are
inferred
from the
similarities
that are observed
among taxa.
Understand the components of a
character-taxon data matrix
.
Distinguish between
rooted
and
unrooted trees
.
Recall the basic procedure for finding/searching for the
most parsimonious
tree(s):
1.
Ignore parsimony-uninformative characters.
2.
Draw possible trees.
3.
For each informative character count the minimum number of steps required on each tree.
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BIS2C
Winter 2011
4.
Sum over all characters to get the “score” (number of steps) for each tree.
5.
The most parsimonious tree(s) is/are the one(s) with lowest score.
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