Download Phylogenies

Zoology 445
Fall 2006
Reading: Chapters 2 & 14 of text
Phylogenies: Handout
I. Constructing phylogenetic trees.
Phylogenetic tree = A graphical representation of the evolutionary history of a group.
Trees are constructed by organizing organisms into groups that share sets of derived characters states (=
synapomorphies).
Synapomorphies are nested, and the hierarchy of synapomorphies replicates the branching events within
the evolutionary history of a group.
Groups are organized using the principle of parsimony = The tree with the fewest number of
steps is assumed to be the correct tree.
AM Jarosz
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Maximize homology (=Similarity between species that results from inheritance of traits from a common
ancestor.)
And
Minimize Homoplasy (= Similarity of characters found in different taxa that is due to convergence,
parallelism or reversals – Not due to common descent.)
Types of Homoplasy reversal.
Another common form of Homoplasy is convergent evolution. The text uses the flippers of whales and
penguins as an example.
Trees can also be constructed by phenetic and maximum likelihood approaches (see Box 14.1, page 562
of text)
Morphology
Molecular Data
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Fig 14.5
Molecular data. Fig 14.6
Which characters to Use?
Informative characters are those found in two or more species within the “ingroup” and fewer
than all the species in the “ingroup”.
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Transposable element data. Fig 14.8
SINEs & LINEs are parasitic DNA that move slowly around the genome.
Classifying the diversity of life.
There is a major effort to change our hierarchical classification.
Figure 14.10
Paraphyletic group = includes some but not all descendants of a common ancestor.
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Note: Section 14.3 of the text was not covered in lecture but is fair game for the test.
\Evolution Zol 445\2006\ Phylogeny Handout.doc
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