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WHALE ANKLES
AND DNA

Whale Connections...
DISCOVERED

 

Larry Flammer

 

EVOLUTION

 

Macroevolution

 SYNOPSIS

 Students follow the Becoming Whales lesson with a look at more recent data (ankles and DNA) to see if their findings (and predictions based on those findings) are confirmed and sharpened. Students compare early whale ankle bones with similar ankle bones in other animals. They then compare sample strands of DNA from a protein found in suspected relatives to arrive at a conclusion about the closest living relative of whales today.

 PRINCIPAL CONCEPT

 Multiple lines of evidence that point consistently to the same conclusions serve to strengthen those conclusions.

 ASSOCIATED CONCEPTS

 Degrees of similarity of structure reflect actual degrees of relationship
DNA can be used effectively to assess biological relationships

ASSESSABLE OBJECTIVES

   Students will....

1. distinguish ankle bones of related individuals from more distantly related individuals
2. compare DNA segments of a gene in different animals, count their differences, and conclude which are most closely related and those more distantly related.
3. recognize the significance of different lines of evidence pointing to the same conclusions.

 MATERIALS

Teacher instructions (this lesson)
DNA Results Table for the overhead (to record results from teams for class to see and compare)
Key for the DNA Results Table for the overhead (let us know if any errors)
Key for DNA Discussion (send request for this with school email address, school name, city, and state to Webmaster)
Whale DNA Activity Strips (to copy and cut apart strips, place all 11 from a sheet into its envelope, or have a lab assistant do this. Make up enugh sets (envelopes) so that each team of 2-4 has a set.
For first time use, you could provide scissors and have students cut them apart, if there is class time.

NEW (3 March 2008)
Science Kit version of
Becoming Whales AND
Whale Ankles and DNA (combined).
If you use this material every year (thank you, very much!), you might want to take a look at the new Science Kit version. It includes the Whale Ankles and DNA segments, along with a very nice class set of (10) pictorial laminated timelines and sets of very sharp whale fossil strips (similar to the ones on the ENSI site, but smaller and laminated for frequent re-use). Go to http://sciencekit.com/product.asp?pn=IG0019348
The kit is described there, along with item number and price:
WW0175086 Evolution of Whales Kit $65.99
If you do order the kit, contact the Webmaster. There were a few minor errors and some other changes that should be included, and if they're not, I'd like to have them sent to you.

 TIME

 Probably about 1 45-minute period for discussing the Ankles assignment, and doing the DNA assignment.
STUDENT HANDOUTS Whale Ankles Activity sheet
Whale DNA Activity sheet
Envelopes with 11 DNA strips (one set per team)
Whale DNA Discussion sheet both sides)

 

 

TEACHING STRATEGY

A. Do the "Becoming Whales" lesson.
B. Suggested sequence for these two activities:
- 1. After completing the "Becoming Whales" lesson, hand out the Whale Ankles Activity for homework.
- 2. Next day, discuss the conclusions from the Ankles activity, then hand out the Whale DNA Activity, along with the envelopes, each containing the 11 strips of DNA to be compared to each other (cut apart). Students, working in teams of 2-4 align the DNA strips (as suggested), 2 at a time, and count the number of nucleotides (letters) that differ between the two strips. Record in the proper space on the grid.

- 3. DNA Discussion. Student teams discuss and complete the DNA Discussion page (2-sides).
- 4. Class: Teams share their results with the class, and note that they come up with essentially similar "Family Trees" (phylogenies). This consensus (conciliance) strengthens the reliability that the data reflect real relationships. You may want to show the key on the overhead, for kids to compare with theirs, or possibly collect discussions (or one per team) to grade, using the key for checking purposes. Please allow for reasonable variations reflecting slight differences in nucleotide counts. If you find that there is total (or major) agreement on numbers that differ with the KEY, please let us know (email the WEBMASTER) with that information.
- 5. Extension: Culminating information, and a suggestion for further (or individual) comparisons with other genes.
- 6. Reflection: Be sure students review the different lines of evidence pointing to the most likely relatives of whales: fossils (including hooves on toes), ankles, DNA.

CAUTION: Unfortunately, students may come away from this lesson with the mistaken conclusion that each of the interediate whale forms were in the direct (llineal) line of descent between the land-dwelling tetrapods and fully aquatic whales. IN REALITY, it is most likely that these "transitional forms" were only "collateral" (cousin-like) ancestors, but showing features that were likely found in their "cousins" that did evolve into modern whales. This subtle distinction may seem unimportant, but to assume that fossils generally fit into a linieal (direct) line of descent conveys the errouneous impression of the long-outdated "Ladder of Evolution" concept. Rather, students should recognize that what we are seeing are the vestiges of many side branches in a diverse BRANCHING TREE of evolution. Be sure to show them (on overhead or LCD projector) the "Family Tree of Whales" diagram (by whale paleontologist Hans Thewissen) to get across this phylogenetic tree concept.

CLICK HERE to see even more clearly where whale evolution relates to the ungulates (hoofed mammals), especially the artiodactyls, and the hippos in that group, based on the latest fossil and DNA evidence. This Provisional Phylogeny of Whales and Ungulates shows approximately the timing and branching points when each group of interest first appeared..

- NEW DISCOVERY: 12.20.07 Nature: Hans Thewissen reports on a likely 48 million year old artiodactyl "little deer-like" ancestor to the whale line. If time, hand out 5-page infomation packet (with questions) about this little creature, found in Kashmir and named Indohyus. This assignment packet is slightly modified from one prepared by teacher Jennifer Wright. After students read the article and answer the questions, discuss this in class, and relate to the "Becoming Whales" lesson (maybe prepare a strip of Indohyus to be added to the time line) and conclusions from the whale ankles and DNA experience. Be sure to take a look at the Oxygen isotope ratios associated with osmoregulation in different early whale fossils.

PROCEDURES

 Students follow procedures on the handout sheets.

ASSESSMENT

 1. Observe participation of team members during the lesson.
2. Prepare questions for a summative test based on the main concepts developed during the experience. If you make a good one, please share with us (webmaster) so that we can share with other teachers.

EXTENSIONS

& VARIATIONS   

See "Extensions" on the "DNA Discussion" sheet.

BETA TEST: This is a beta version of this lesson, not used in classrooms yet. We would appreciate any and all feedback, with your constructive suggestions, its effectiveness, and its engaging qualities (i.e., did the kids enjoy it?)
Contact Webmaster

 ATTRIBUTION

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: Larry Flammer

2. Adapted to website by L. Flammer 4/19/07

3. Revised 11.08.07

 

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