Make sure students have read introductory material on how trees are constructed
and understand the difference between ancestral and derived traits. Show
class a phylogeny, with examples of progression. Ask them to identify which
characters could be used to re-construct the same phylogeny. Are there alternate
phylogenies? Discuss how convergent evolution might affect the construction
of trees (homologous vs analogous structures).
: Two optional families of related species: 1)
Nails/screws - get a wide variety of flat-head nails, screws, wall hangers,
etc. Nail history:
2) Paperclip family: metal / plastic paper clips, W type clips, binder
clips, etc. Here is a web link to an archive of various sorts of historical
paper clips http://www.officemuseum.com/paper_clips.htm
Alternative or addition to fastener phylogeny
: 1) Echinoderm phylogeny:
if facilities permit: order a variety of echionoderms and keep in aquaria
(sand dollars, sea stars, brittle stars, sea cucumbers, etc). Get students
to examine animals and create phylogenies based on observed characters.
Alternative to using live animals would be to use dry samples of sea stars,
sea urchins, etc. If you have a bird collection or greenhouse available,
it would also be a good source of specimens to examine.
Make sure students have sufficient background in molecular biology : structure
of DNA, substitutions, different types of changes in amino acide - transitions
versus transversions (and the implications that different types of changes
have for evolution).
Go over different types of methods to estimate phylogenetic relationships,
and explain the benefits and problems with each.
Maximum likelihood is conceptually difficult for most undergraduates,
especially those with little statistical background - introduce method with
coin flipping example - contrast probablity of getting 50/50 heads/tails
if a coin is tossed 100x (which most students will be familiar with) and
maximum likelihood method of using actual data from 100 tosses to determine
Propose several hypothetical situations (fossil specimens, mtDNA information,
small number of character states, etc) and ask students which would be the
best method for resolving relationships among samples.
NCBI has a portion of their web site devoted to tutorials :
which are very helpful. If students are having difficulty navigating GenBank,
refer them to this site for help. The "nucleotide tutorial" has a nice guided
search of Mycobacterium tuberculosis for sequences coding for penicillin
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