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Investigating Evolutionary Questions
Using Online Molecular Databases

Bats/Birds, Whale Feet, and Reptile Feathers?


From a Lesson Published in
The American Biology Teacher
by Mary Puterbaugh & J. Gordon Burleigh




& Relationships

 Revised versions of instructions have been added to the Student Materials. Please try them out, let us know if they work ok.


Students are guided through a process in which three questions are addressed by retrieving beta hemoglobin sequences from online databases, and using online tools to compare those sequences in student-selected animals. The questions: (1) Are bats birds, or mammals?; (2) Are whales more closely related to artiodactyls, or perissodactyls?; and (3) should birds be included in the class Reptilia?


Degrees of biological relationship can be inferred from comparisons of selected molecules.


Degrees of biological relationship based on molecular comparisons should be more or less consistent with such relationships inferred from morphological and paleontological studies.

Online molecular databases and online tools for analyzing and comparing molecular sequences can be useful and effective teaching aids in high school biology.


   Students will....

Given three different animal species [available in the SWISS-PROT database], the student will be able to suggest which two species are most closely related, based on a comparison of the amino acid sequences of their beta hemoglobin.


For each student or pair of students:
1) Background and Overview package
2) Packet of figures for reference
4) Copies of two articles for reference
3) Packet of tables for data collection
5) One computer with access to the Internet and with a word-processing program and an Internet browser running simultaneously, and students prepared with basic internet and word-processing skills.


About two 45 minute periods, or equivalent.



A. Student Information Handout, with ...
- Lesson Background and Overview
- Detailed Instructions for each of the 3 main parts (+ optional part)

B. Tables for Data Entry and Questions to be answered

C. Packet of figures for reference

D. Copies of two articles for reference (students can obtain these from local university library, or can be teacher-provided).



   Click here to get the four-page Teacher Package
in PDF format. This contains background information, an overview of the entire 3-part lesson, a list of materials, references, and editorial comments for this online version. For reasonal responses to Student Tables and Questions, request from webmaster using your school email address.

This lesson requires some understanding of the following:
- basic structure of proteins (as a chain of amino acids in a functional sequence)
- some skill in basic use of computers, switching between internet web sites and a resident word processor, by at least one person per team.
- classification of organisms depends directly on the degrees of similarities and differences between groups, and the evolutionary relationships inferred therefrom.

These pre-requisites should be presented in a brief "preparation session" or two, if not already learned in the current course content or previous courses.

This lesson could be appropriately included with a unit on classification, introduction to evolution, or the application of molecular structure to address biological questions.

Prepare overhead of the Calvin and Hobbes cartoon strip(s) described in the Teacher Background and Overview package.

Prepare a classroom set of the packet of figures showing the series of online frames to be accessed during the tutorial (optional).

Prepare packets of Student Information Handouts and Tables for Data Entry and Questions, enough for one per team (of 2-4 students per team), or one per student.

Encourage students in every team to thoroughly discuss the questions asked, to be sure that everyone on the team understands the team answers and the reasons for those answers, and that each person is accountable to respond to directed questions during class discussion.

Prepare copies of the two articles to be read for reference, enough for individuals to take home at least one of the articles to read (making sure that at least both articles are read by students in the same team.)


Scientists are using rapidly growing online databases, and powerful online analytical tools, to investigate an abundance of biological questions. What is not widely realized is that, with a little guidance, these resources can be used by high school students for real-time questions about evolution and other topics in biology. This lesson provides an excellent guide for doing just that. Students are guided through a process by which three questions are addressed: (1) A seemingly whimsical problem of why bats are not birds, in which their beta hemoglobin molecules are compared; (2) a more practical problem, also using beta hemoglobin, to shed light on the ancestry of whales in even-toed vs odd-toed hooved animals; and (3) considering the question of whether birds should be included in the class Reptilia.

See Procedural details presented in the Student Information Handout.


Students will demonstrate their skill in using online molecular databases and analytical programs to answer a typical biological/evolutionary question.





In addition to the extensions and variations suggested under Editorial Comments (item #4) in the Teacher's Packet, consider the following:

- 1. This lesson provides a very nice extension from a lesson on whale evolution "Becoming Whales", (perhaps more appropriate for high school / middle school levels) in which students "experience" the sequence of discoveries in which a number of transitional fossils gradually filled in much of the "gap" between the purported terrestrial whale antecedents and modern type whales, based on morphology. Other types of evidence are also explored, as are very recent comparisons of "whale ankles and heels" and their possible relationship to hooved animals (ungulates: perissodactyls vs. artiodactyls). See our Whale Ankles and DNA lesson as an alternative.

[For Part II, if you would like your students to explore the discoveries and analyses of the evolution of whale morphology, see the "Becoming Whales" lesson on the ENSI site.]
[For Part III, a very useful article ("Dinosaurs and Birds, an Update") by UC Berkeley paleontologist, specializing in bird evolution, would be worth reading here. It is available in its entirety on the ENSI web site.]

- 2. Students can try different molecules and/or different species to see if their conclusions are confirmed.

- 3. Look for species whose major group assignments have been puzzling in the past. For example, compare lungfish, coelacanth, other fishes, and amphibians, or compare peripatus with (other?) arthropods and annelids, or brachiopods with some deuterostome and proterostome, to see which group they are closest to. (May need to look at their cytochrome c or other common proteins to find something sequenced for all species to be used in the comparison).

- 4. Students can explore different online databases and different online analytical tools to address such problems.

- 5. We also have a nicely structured treatment of beta hemoglobin comparisons in primates on our ENSI site, which provides the amino acid sequences showing differences, and uses the matrix data to discuss relationships, build a cladogram showing where humans and other primates fit into an evolutionary scheme, and to illustrate the molecular clock concept.

- 6. An excellent extension of this entire experience is for your students to experience how scientists use comparison data (e.g. morphology, amino acid sequences, etc.) to build evolutionary trees as phylogenetic hypotheses, and the kind of parsimonious decision making which is involved here. It just so happens that such a walk-through is provided in the September 2001 American Biology Teacher (vol. 63, no. 7, pages 518-523): "The Comparative Method, Hypothesis Testing & Phylogenetic Analysis" by Fred Singer, Joel Hagen, and Robert Sheehy. Web sites where online data bases can be accessed are included.

- 7. Another excellent tutorial, which includes the use of free online tools for building phylogenetic trees, and uses DNA databases to get and compare selected DNA sequences, is in a recent article in the ABT journal: "Building Phylogenetic Trees from DNA Sequence Data: Investigating Polar Bear & Panda Ancestry" by Caroline Alexandra Maier, The American Biology Teacher, vol. 63, no. 9, Nov/Dec 2001, pages 642-646. Like the protein sequencing tutorial, students can use the skills and resources to answer many other relationship questions.

- 8. We welcome, in fact encourage, your feedback from your experiences using these lessons. Your comments, questions and suggestions will be shared with Dr. Puterbaugh, and may well be reflected in future revisions of this lesson. Dr. Puterbaugh has indicated she appreciates any such feedback directly (via her e-mail or snail-mail addresses) if you prefer.


See the list of additional references in the Editorial Comments of the Teacher's Packet.


Some of the ideas in this lesson may have been adapted from earlier, unacknowledged sources without our knowledge. If the reader believes this to be the case, please let us know, and appropriate corrections will be made. Thanks.

1. Original Source: "How-To-Do-It" article in The American Biology Teacher, August, 2001 (vol. 63, no. 6, pages 422-431),
by Mary N. Puterbaugh and J. Gordon Burleigh.
Permission to use kindly provided by NABT and Mary Puterbaugh.

2. Edited and adapted for website by L. Flammer 10/14/01


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