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Whale Search
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Steve Hammack
Los Gatos High School
Larry Flammer
Del Mar High School

Possible Audiences:

high school / undergrad students


Brief Overview

The following situation could be used as an extension to an activity in which students experience the gradual accumulation of fossil material which paints an increasingly clear picture of cetacean evolution from earlier mammalian tetrapods (ENSI lesson: "Becoming Whales"). The resulting phylogenetic tree comes into question with the appearance of new studies (molecular and fossil). This creates a problem which can be addressed objectively using molecular data banks and analytical tools.

Traditional interpretations of whale evolution based mainly on fossil evidence suggest artiodactyls as the group of living mammals most closely related to cetaceans. Recent molecular studies have suggested that hippopotamids may be the most closely allied sub group of artiodactyls to fill this role. However, very recent fossil material (ankle bones of archaeocetes and primitive artiodactyls) seem to indicate that hippos might not occupy that position, that other artiodactyls might fit just as well, if not better.

Question: Are hippopotamids indeed the living artiodactyl group most closely related to cetaceans?

Hypothesis: Hippopotamids are the living artiodactyls most closely related to cetaceans.

Predictions: If this is true, then sequence comparisons of several different proteins should all (or mostly) reveal fewer differences between those of cetaceans and hippopotamids than between cetaceans and other artiodactyl groups.

Test: Different teams of students test the hypothesis by selecting one or more molecules and representative animals in different families of cetaceans and artiodactyls, and compaing the sequences of those proteins. A useful approach for doing this (if the students have not had the experience) would be to do the ENSI/NABT tutorial: "Investigating Evolutionary Questions Using Online Molecular Databases." Teams would report out their respective results and attempt to reach some consensus in a class discussion.



Project Materials

Online Data Bank of protein sequences of selected proteins in selected animals. Our goal would be to compile fairly large lists of reasonable candidates (of proteins and possibly animals) from which student teams could make their selections.



Resources and References

"Whippo Data" site (numerous sequences fitting the desired material)
Biology Workbench



Future Directions

Add proteins
Consider adding DNA sequences; pseudogenes, ....

Add exercise in using cetacean - artiodactyl trees to illustrate legitimate variations (using MacClade)