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BECOMING WHALES

Experiencing Discoveries of
Whale Evolution
OR...
"The thrill of discovery...
The loss of de feet"

by Larry Flammer

 

NATURE OF SCIENCE
Basic Processes

EVOLUTION
Geological/Paleontological
Patterns

 New PowerPoint program on Whale Evolution
Not for replacing lessons, but for intro and review.
If problems getting this big file, contact webmaster.

 SYNOPSIS

Students will experience the historical discovery of fossils that increasingly link whales to earlier land-dwelling mammals. This experience reveals how scientists can make predictions about past events, based on the theory and evidence that whales evolved. Such predictions suggest the age and location of sediments where fossils of early whales would most likely be found, and even their traits. This lesson also provides confirmation, with multiple independent lines of evidence, that there is a series of intermediate forms, showing gradual accumulation of changes, linking certain terrestrial mammal groups with modern whales.

Ambulocetus natans in action. A reconstruction of an early close cousin of whales.
Shown here with the kind permission of artist Carl Buell.

 PRINCIPAL CONCEPTS

1. The Process of science: hypotheses lead to predictions which lead to tests which can challenge the validity of those hypotheses.
2. Transitional forms are generally a mosaic of traits, suggesting that some traits evolve faster than others.

 ASSOCIATED CONCEPTS

1. New evidence can lead to major changes in scientific concepts.
2. Fossils exist of certain mammals with traits intermediate between terrestrial mammals and modern whales, showing the gradual accumulation of whale traits, and the loss of terrestrial mammal traits.
3. These fossils are found in sediments of the age and with the environmental evidence appropriate to forms transitional between terrestrial mammals and modern whales.
4. Geological events have had profound influence on the pathways taken in evolution.

ASSESSABLE OBJECTIVES

   Students will....

1. Students will recognize the elements of the process of science as reflected in this lesson.
2. Students will recognize the role of predictions in science, and how this helped clarify whale evolution.
3. Students will explain the evidence leading to a possible revision in the likely ancestors of whales
4. Students will give examples of the mosaic nature of evolution in whales.
5. Students will identify which whale-like traits appeared earliest, and which ones appeared later.
6. Students will explain how the tectonic movement of India into Asia caused changes in the Tethys Sea, and how those changes may have contributed to the emergence of whales.

 

 

MATERIALS

   CLICK HERE for Index to pictures, for printing.

   CLICK HERE for Index to PDF Text Files, for printing.

For a convenient copy of this entire lesson for easy, condensed printout (8 pages), click on INDEX to PDF TEXT FILES (above).

For Teacher Use:
New PowerPoint program on Whale Evolution

Not for replacing lessons, but for intro and review
If problems getting this big file, contact webmaster.

Whale Hunt Narrative
(for Teacher-Directed fossil hunt, shorter version)

For Teacher Overheads:
1. Classroom timeline of the Cenozoic era (past 65 million years; 6 pdf pgs)
2. "Whale Lengths" (optional, info for full size whale strips; pdf page)
3. "Some Modern Whales" (optional, pictures for cutouts and overhead)
4. "Pakicetus Variations" (optional, pictures for overhead)
5. "Family Tree of Whales" (optional, picture for overhead)
6. "Whales as Mammals" (What Kind of Creature is a Whale?; pdf page)
7. "Provisional Phylogenetic Tree of Whale Relatives, Based on DNA Analysis" (optional, picture for overhead)
8. "Osmoregulation Diagram of Oxygen-18 to Oxygen-16 Ratios in Whales" (optional, picture for overhead)
9. "Continental Drift and the Tethys Sea" (optional picture)
10. "Whale Collection Sites in Pakistan" (color picture)
11. Video animation showing India being rafted into Asia, with horizonatl view and sound effects of the continental crunch, scraping the Tethys seafloor and scrunching it upwards to form the Himalaya Mountains.
12. Cartoon of four-legged whale going to sea, while four-legged fish is coming ashore. See cartoon below, under the Assessment section.
13. Whale Evolution Video (chapter 2 of the PBS show: Great Transformations); list of contents of this video;
YouTube version of the video.
14. Another whale evolution video clip (7 min.) from PBS: Evolving Ideas: How Do We Know Evolution Happens?

For each team:
1. Timeline of the Eocene epoch (55 to 34 mya; 2 pdf pages): provided, or to be made by each team.
2."Whales in the Making" page of picture strips of fossils and reconstructions of 6 whale-type mammals (to be cut apart, #1-5 placed in envelopes, and # 6 handed to teacher to hold.
3."Discovery: Whales in Transition": Background, Procedures, Narrative, and Discussion Questions (student handout, 3 pdf pages)
4."Whale Evolution Data Table" (pdf, optional), fill in from resources.
5."Origin of Whales and Power of Independent Evidence" article" (excellent resource; 11 pdf pages; optional).
6. OPTIONAL: WORKSHEET for team- or individual student-guided search.

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). There is also a nice set of modern whales included (scale models, of course!).
Go to http://sciencekit.com/product.asp?pn=IG0019348
The kit is described there, along with item number and price:
WW01750M86 Evolution of Whales Kit $74.99
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 send them to you.

 TIME

Should require no more than about one 45 min. period. Could be expanded into two such periods or one longer period.
STUDENT HANDOUTS

"Discovery: Whales in Transition": Background and Procedures

Eocene timeline (one 2-page set per team)

Picture strips of fossils and reconstructions of 6 whale-type mammals
(in envelopes, or on sheet to cut out; see Illustrations Index for "Whales in the Making" page). (1 set per team)

Other optional pages as listed in Materials.

 

 

 TEACHING STRATEGIES & PREPARATION

Because this lesson provides an excellent opportunity to understand important elements of the Nature of Science , be sure to read our General Background Information, with our Rationale and our Approach, and tips for Presenting the lessons for maximum effect and Dispelling some of the popular myths about science.

In any of the discussions expected with the class, select a few key items (important concepts) that lend themselves to interpretation, and introduce class to the Think-Pair-Share (TPS) routine dealing with those items. This is how "Active Learning" is done.

SEE NEW MATERIAL ON WHALE EVOLUTION
on the Understanding Evolution website
Several excellent figures you could include
in a PwerPoint presentation -
Lots of good information, too.
9 March 2011

STRATEGIES:
This lesson can be used in three different contexts:
a. As part of your introduction to the nature of science, it will provide a novel and intriguing vehicle for exploring some of the less often appreciated elements of the process of science.
b. As part of an introduction to classification, especially when you consider organisms difficult to classify, since they don't fit perfectly into one classical group or another, depending on how the diagnostic traits of the groups are defined. Makes logical segue into evolution.
c. As part of your introduction to evolution, this presents an excellent example of transitional forms (a pattern which appears again and again in the fossil record), showing the mosaic nature of evolution, and the gradual accumulation of new traits. [Probably the best way to use this lesson, especially for novice teachers, as a low-cost alternative to the "skulls lab".]

PREPARATIONS:
1. TEACHER: Prepare a Main Classroom Timeline of the past 65 million years (Cenozoic Era). Use a 6-foot strip of narrow butcher paper, or assemble the pre-printed version (see pdf files in the Materials section). Ideally, use the same scale as the students will use (1 inch = 1 million years). Have it marked at every million years, clearly numbered from NOW near the top, then 1 mya, 2 mya, etc. down to near the bottom end (65 mya). This will require about 65 inches (in this scale). Next, mark and label the range of each epoch ("mya" = millions of years ago):
  last 10,000 years (0.01 inch) = Holocene (thin black line at top)
2 mya - 10,000 years ago = Pleistocene (orange)
5-2 mya = Pliocene (blue)
24-5 mya = Miocene (yellow)
34-24 mya = Oligocene (green)
55-34 mya = Eocene (red)
65-55 mya = Paleocene (brown)

[This scale - 1 inch = 1 million years - is chosen for its convenient size, especially to accomodate the whale-strips used. You might prefer using metric units; if so, we recommend 2 or 3 cm per million years so the whale strips will fit. For other scales, and suggestions for a highly recommended full classroom-size timeline for the 4.5 billion year history of our Solar System, click here.]

Epochs: Color-in the vertical strips with different contrasting colors for the epochs to help students see the range of each epoch more clearly (see suggested colors above). Place the name of each epoch in large letters in its proper place. (Colors and names are already done in the pdf charts provided). This chart should be placed vertically in the room so students can see the full range. Their "working" timelines will just be the Eocene epoch, but they can see where it fits relative to the other epochs shown on the classroom timeline. These ranges are the currently most accurate (1999), according to the Geological Society of America.
For easy re-use, have the timeline laminated (Kinko's does this for a moderate fee), and also have your teacher-set of whale strips plastic-laminated, to which you can affix velcro pads or double-stick tape so you can demonstrate the activity as the class does it.

2. TEACHER: Cut apart the 6 strips of fossil whales (or have this done by lab assistants). Put #1-5 into an envelope* for each team. Keep all #6 (Ambulocetus) strips (to hand out to each team AFTER someone in each team has drawn the whale fossil traits expected between 46 and 50mya.)

*[A clever, and probably better alternative: put each strip into its own numbered envelope, so each team gets a set of 5 envelopes, numbered in proper sequence. This would discourage students from moving ahead and placing strips immediately at their respective time levels, and encourage them to wait for the narrative description before they remove each strip from its envelope in turn, as if the fossils were being gradually "unearthed" over time, creating a sense of anticipation and real "discovery" which emulates the real sequence of discovery over many years. This would require many more envelopes, but is probably worth it! We thank Victoria Evashenk (ENSI 1992) for this useful suggestion.]

3. TEACHER: Find and display pictures of modern whales from the two living suborders: the Odontoceti (toothed whales, e.g. sperm whales, Orcas, and porpoises), and the Mysticeti (the baleen whales, e.g. the California gray whale, humpbacks, and blue whales (largest living animal, at 90 feet long). In addition, display pictures of the skeletons of a whale from each group (examples in Materials Index). Prepare paper strips for students to SEE actual whale lengths (see Extensions).
4. Prepare copies of handouts, one copy for each team.
5. Prepare copies of resource materials (one for each team), and have available as team requests.
6. Students should work in teams of 2-4
7. EACH TEAM prepares its Eocene timeline, using 2 sheets of notebook paper taped together end to end in vertical format, or a two-foot strip of narrow butcher paper. Optional: to save time, this Eocene timeline may be pre-constructed, and used repeatedly by each class (see Materials for pdf printout).
8. TEACHER: Come to class on the "dig day" dressed as if you were going on a paleontological dig, with wide brimmed hat, sunglasses, hiking boots, grungy shirt and pants, and your geological pick. You can even heighten anticipation by announcing the dig the day before, providing "field trip permission slips" for parent signatures (if the school normally requires these), and ask students to wear "proper fossil-digging clothes"; lunches, and cameras are optional!

 

 

 

PROCEDURES

PROCEDURES

Be sure to consider the suggested introduction described under Extensions, #1-3 (below)
....And ALSO the most recent suggestions at Extension #18


1. When all timelines are done, and fossils are cut out and in their envelopes, Announce "We're going on a dig .... we're going to look for whale fossils. Are you with me???? Good, let's go!" ["Close your eyes and visualize!"]
2. One student in each team starts reading the "Discovery: Whales in Transition" narrative (Part C) to the team.

Optional: teacher, as the "fossil dig coordinator," can read the narrative to the class, or do this from memory. See shorter NARRATIVE provided in pdf format in the page of materials. Doing it this way keeps the entire class together at the same stage, allowing teacher to inject appropriate comments of enthusiasm and encouragement and ecitement, OH MY!

3. As each whale or near-whale species is mentioned, a partner in each team finds and places that strip on the team timeline at the appropriate time level. If desired, the teacher can do this, too, placing each whale strip on the classroom timeline as visual reinforcement for the class. Use the plastic- laminated timeline and whale strips, with velcro or double-stick tape for this.

4. Be sure to note that the sequence followed in the narrative closely reflects the sequence of discovery, so you get a real sense of the growing excitement amongst paleontologists as they found each fossil piece of the early whale evolution puzzle, gradually filling it in with specimens showing predictable intermediate traits between their likely land-dwelling ancestors and the totally marine whales of today. Advantages of the teacher presenting the narrative:
- 1) all teams can be paced through the discovery together, and
- 2) the growing intrigue can be dramatized!.

5. When all 5 strips are in place, student teams predict what an intermediate form would look like to fill the critical gap between 50 and 46 mya. Circulate. As each team shows its "intermediate" drawing, hand them the last strip (#6) to place on their timeline and compare with their prediction.

6. When all fossils are placed in position, students answer the discussion questions. Be sure they discuss each question (and possible answers) with their teammate(s), and record on a team sheet.
7. STUDENTS: be prepared to ask questions and join in classwide, teacher-directed discussion when done.
8. TEACHER: See the Extensions for tips and ideas you might want to include as part of class discussion.
9. HOMEWORK: As a possible take-home (or extra class day) assignment, students can be asked to gather more detailed information about each species (see details on student handouts: Whale Evolution article and data sheet).

10. CAUTION: Unfortunately, students may come away from this lesson with the mistaken conclusion that each of the intermediate whale forms were in the direct (lineal) 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 lineal (direct) line of descent conveys the erroneous 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.

With studies of the DNA from living whales and other living animals that could be most closely related (releatively recent common ancestor), we 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. IF you plan to have your students do the WHALE ANKLES AND DNA, do NOT show them that Provisional Phylogeny, since it gives away what they would discover in that lesson.

Furthermore, students should focus more on the mosaic accumulation over time of a series of new features modfified (derived) from ancestral features over time, not the species per se. The fossil remains collected simply reveal that those respective features existed in those related species at that period of time. See Scientists Confront Creationism (2007), Edited by Andrew J. Petto and Laurie R. Godfrey., pages 197-225 by Kevin Padian and Kenneth Angielczyk for a clear explanation of this.

FOR AN INTERESTING DISCUSSION,
scroll down to the cartoon saying "It's all yours." This could even be part of your assessment.

ASSESSMENT

1. Ask students to list the elements of the process of science reflected in this lesson and give examples of each (for example):
a. recognition of a problem: how did whales emerge from some land-dwelling mammal?
b. hypothesis formation: they evolved by gradual change over time, losing terrestrial features, and gaining aquatic adaptations.
c. predictions based on hypothesis: what to look for (fossil whales with legs), where to look (Eocene sediments from warm shallow seas)
d. searching for evidence: (digging for whale fossils in Pakistan, etc.)
e. independent evidence of fossil sequence (oxygen isotope ratios in bones and teeth)
f. popular "generally accepted" concepts replaced with new concepts, based on new evidence (DNA analysis and ankle features), suggesting mesonychids not ancestral to whales.
2. Build other questions (essay, or carefully crafted multiple choice questions) around the Assessable Objectives.

whale/fish cartoon
Whale/Fish cartoon, from New Yorker magazine, March 2, 2009, page 49.  Permission to use was kindly provided by cartoonist Danny Shanahan.

Just before you finish this lesson:
Show the cartoon on screen. Ask students what questions it raises. Encourage students to offer replies to those questions, and engage in general discussion. In the process, try to get responses to these:
1. Why do you think I’m showing this cartoon here?
2. What story does the cartoon suggest happened?
3. In what two important ways does this cartoon conflict with the actual records of evolution?
BEST RESPONSES TO #3:
a) tetrapod whales-to-be didn’t look like whales; those legs wouldn’t carry the weight;
b) tetrapods-to-be fish moved onto land in the Devonian (395 mya), long before whales emerged (about 55 mya), so they wouldn’t really pass each other at the water’s edge.

[To use cartoon, click and drag it to your desktop. Or, get it at www.indiana.edu/~ensiweb/images/cartoon.whale.jpg

 

 

 

EXTENSIONS

& VARIATIONS   

NEW FOLLOWUP LESSON:
WHALE ANKLES AND DNA
Take a look at this; uses new data that students analyze, revealing the closest living relative of whales.

In this lesson, students search for the nearest mammal cousins of whales by studying and comparing the ankles of early whales, mesonychids, early perissodactyls and early artiodactyls, and discover the striking similarities to the artiodactyls. Narrowing down the search, a portion of DNA from the gene for making beta casein (milk protein) is compared in a number of mammals, including whales and several artiodactyls, and discover the striking similarity to the DNA of hippos!

UPDATE...

- 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 information 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.


AN EFFECTIVE AND ENGAGING INTRO TO THE "BECOMING WHALES" LESSON:
The following suggestions would be very helpful, especially with younger students in middle school settings. See the PDF listings (materials), try the Teaching Outline, whch choreographs many of these ideas.

1. Obtain and place large pictures of modern whales near the top of the classroom timescale, along with their skeletons. Point out that the earliest odontocete and mysticete fossils are only about 34 my old (upper Eocene).

2. Next, demonstrate the actual sizes of some modern whales AND the fossil whales to be discovered. An easy way to do that is to prepare strips of adding machine tape cut to the appropriate lengths, each clearly labeled with the name of the whale represented, and its actual (average or maximum) length (in meters). This could be a fairly easy assignment for your students to do: each team could be assigned one or two of the whales, and cut off the needed length of paper strip to do this. [Teacher can provide a measuring strip of tape, marked off in cm, along a counter top to facilitate this.] Students can hold up their whale strips as they are discussed, or they can all be mounted on a wall in the room. Display or hand out the Whale Sizes data table with these lengths (pdf file in Materials section.)
A more convenient variation is to use corrugated border strips (which come in 50 foot lengths of various colors, available for a few dollars in educator's or office supply stores). These are pre-measured, and much more durable for re-use each period.

3. GOOD INTRODUCTION: Establish or confirm that whales are mammals, and why we assume that they must have evolved from a particular group of four-legged land mammals millions of years ago. You can use the "What Kind of Creature is a Whale?" outline on your overhead (see pdf index in the Materials section). The comparison of various features between whales and a fish or a cat is taken directly from the delightful online interactive experience: the "Whale Evolution Kiosk" (described at the end of the Extensions and Variations section).
You could also display the picture of a dolphin embryo with a hind limb bud! (with kind permission of Hans Thewissen).And you could show the picture of a nursing whale, and share information about whale hair, the most widely recognized traits of mammals.

DISCUSSION EXTENSIONS AND FOLLOWUP:
4. Growing out of discussion question #3, you might find it useful to show pictures of the ancient Tethys Sea which existed prior to around 55 mya between the landmass we now call India and the Asian mainland. The Mediterranean represents the westward extension of that sea, but the continental drift pushed India into Asia, pushing up the land mass to form the Himalayan Mountains (and Mt. Everest), and eliminating this eastern portion of the Tethys Sea. If there is an animation in your department showing plate tectonics (on a laser disk, CD, or online), show it to your class, using stop action to step through the stages showing were India moves into Asia. The timing of this event coincides nicely with the Eocene, during which many long-isolated mammals on the rafting India were able to move across to the Asian mainland (and vice versa), introducing a major increase in new competitions and resulting in active selection episodes and increasing diversity. Whale evolution seems to have emerged from that geological event and the resulting biological upheavals. [See PaleoWorld video described below.]

5. During discussion question #5, ask for other possibilities one might expect for the body form of Pakicetus. Then, show the diagram of "Pakicetus 2", with one reconstruction found on a Greek (?) museum website, (also in the PaleoWorld video described below in #8). If possible. show the latest version on Thewissen's site (see below), based on the new post-cranial fossils. Discuss what clues might suggest the features shown here (remember, we only had skull fossils when this lesson was created, no post-cranial parts of the skeleton). Hopefully, students will point out the early whale-like teeth and ears of Pakicetus, so without any post-cranial bones, an artist might easily assume tail flukes. Pakicetus 1, shown on the strip, was found in Zimmer's book, page 203. [Pay particular attention to the whale flukes on Pakicetus 2; would they be there that early, especially since Ambulocetus probably had none?]

6. After class discussion of question #9, display the Family Tree of Whales diagram on the overhead (found on Hans Thewissen's web site, but available in Materials). Note how the several archaeocetes are shown as colateral branches from the direct line of descent to modern whales. A further extension of this could be to show the Provisional Phylogenetic Tree of Whale Relatives (a type of cladogram) showing how whales appear to relate to hippos and other artiodactyls, based on recent DNA analyses (Nikaido, et al, 1999). The earliest mesonychids existed before the earliest artiodactyls, and cetaceans are deeply nested within the artiodactyl tree, as a sister family to the hippopotamids (suggesting that the cetaceans be re-classified as an artiodactyl family rather than their classical status as a separate order), so any connection between mesonychids and cetaceans now appears to be more remote. This close affinity to the hippo family is reinforced by the work of Gatesy, et al (1999) in which numerous DNA sequences were simultaneously analysed in several different species of cetaceans and artiodactyls, producing their "WHIPPO" data sets. See the excellent discussion of these developments in Evolutionary Analysis by Freeman and Herron (chapter 13). This is a chance to point out how ideas in science can change with new information and perspectives. [NOTE: This change is still not settled. Some whale scientists have suggested that the DNA data are subject to different interpretaions.]

7. A very nice example of another independent line of evidence which reinforces the paleontological evidence indicates habitat changes associated with early whale evolution. This can be seen in the Osmoregulation Diagram showing the relative percentage of the Oxygen-18 isotope (significantly higher in the teeth and bones of marine cetaceans than in those of freshwater cetaceans). This is due to their incorporation of the particular ratio of oxygen isotopes in fresh vs. salt water ingested. The earliest archaeocetes (e.g. Pakicetus and other Pakicetids) have lower O-18 ratios, associated with a freshwater habitat, while Indocetus (and Rodhocetus), and Zygorhiza (Gaviacetus), very similar to Prozeuglodon and Dorudon, all have higher ratios, indicating a fully marine habitat. Ambulocetus data show a wide range of O-18 levels, suggesting they lived in a wide range of salinities, as one might expect for a clearly transitional form. The original work on this was published by Thewissen, Roe, and others in 1996.

8. If you can get a good video of whale evolution, it might provide further reinforcement and perhaps raise further questions for discussion. There is a useful 15 minute segment in the WGBH-PBS-Evolution series (first part of show #2). An older (1994) but interesting half-hour tape in the "PaleoWorld" series was entitled "Return to the Seas", possibly still available in a collection of their tapes, through Carolina Biological Supply. The major caution is that this video gives the impression that each of the "transitional whales" evolved into the next more recent species directly, even using "morphing" animation to show each species gradually changing form to become the next species in time, as a series of "links in a continuous chain of life", a long outmoded idea now replaced with the far more likely picture of "cousin" relationships. On the other hand, there are nice references to how the movement of India into the Asian continent caused the Tethys Sea to become shallow and saltier, creating a rich food supply for any creature able to take advantage of it, and providing a long term selective pressure favoring adaptations to specialize in such feeding opportunities in the marine environment. The result: whale evolution.

9. If you can, prepare and mount a scaled linear Earth Timeline around your room (for the past 4.5 billion years), with the last 540 million years somewhat detailed into the 3 major eras, and showing the main life forms characterizing those eras. You can nicely show where whale evolution fits into the total scheme of time, in relation to the age of dinosaurs, human evolution, and any of the many other events and features of geological time. The constant presence throughout the year of this timeline helps to reinforce the deep time concept, the spaced-out sequence of events, and provide a convenient focus from time to time to point out when various biological events occurred. For a few approaches to help with this, see the "Time Machine" lesson on this site. As part of your introduction to geological time, be sure to consider the short lesson on Deep Time on the site, which explains how scientists actually measure time on that scale, and why they are so confident of its accuracy, providing a critical challenge to anyone claiming a Young Earth age of only several thousand years.

10. A question which may arise when students see that the archaeocetes seem to occupy the Eocene, and modern type whales are not found below the Miocene (on the classroom timeline of the Cenozoic), is "Why no whale fossils in the Oligocene?" You can find the answer to this in the abbreviated version of Kathleen Hunt's "Transitional Vertebrate Fossils" on this site. Read especially parts B-1 and B-3. Actually, there ARE some archaeocete fossils in the Oligocene, but they're fairly fragmentary. There is also a fair number of archaeocete fossils spread through the middle-to-upper Eocene, but they are clearly whales, very similar to Dorudon, so they weren't included in the lesson, and this seems to leave an apparent "gap" which doesn't really exist.

11. If your class has ready access to the internet, (especially for advanced classes), an excellent extension of this lesson is the tutorial on this site: "Using Online Molecular Databases to Examine Evolutionary Questions." This lesson takes the student through the process of gathering amino acid sequences of beta-hemoglobin in several different species from an online database, using an online tool to compare the differences in those sequences, then discussing what this indicates in terms of relationships. Comparing whale hemoglobin with that of other animals is part of this exercise.

Be sure to take a look at our WHALE ANKLES AND DNA. It uses new data that students analyze, revealing the closest living relative of whales. In this lesson, students search for the nearest mammal cousins of whales by studying and comparing the ankles of early whales, mesonychids, early perissodactyls and early artiodactyls, and discover the striking similarities to the artiodactyls. Narrowing down the search, a portion of DNA from the gene for making beta casein (milk protein) is compared in a number of mammals, including whales and several artiodactyls, and discover the striking similarity to the DNA of hippos!

12. The latest chapter in whale evolution was added with the simulataneous publication in late 2001 of two reports which concur that, based on the analyses of newly found ankle and heel bones of early archaeocetes (in Pakistan), whale origins are strongly associated with the origin of artiodactyls (even-toed hooved animals). This is consistent with recent molecular studies which also suggest this close tie. Neither study specifies a closer hippopotamus connection necessarily. Both studies put the mesonychid connection as more remote than once thought. See the four articles listed below for 2001, in Nature and Science for details. The Nature article (by Thewissen et al) also has excellent graphics of the post-cranial skeleton of Pakicetus, along with a very nice reconstruction by Carl Buell, who created the beautiful action picture of Ambulocetus shown at the beginning of this lesson. Also. see the new addition to our "Great Fossil Find" lesson, a page with those Pakicetus fossils which are cut apart for students to "find" and reconstruct as they are found, then discover that it is an early WHALE!

13. VISIT THE WHALE EVOLUTION KIOSK. This is a new, very clever interactive online experience for your students, created by Lara Sox-Harris at San Jose State University, who has kindly consented to this link. When you click on the title (Whale Evolution Kiosk) above, it will take you into a self-guided tutorial on the necessary elements of whale anatomy, fossils, DNA, and classification. These will all provide the mutually reinforcing evidence for whale evolution, all in delightful animations and interactions. Help your students with a guided tour of the kiosk, providing more focus, and a way for you to confirm that they probably did indeed visit the site, give them the Whale Evolution Kiosk Worksheet. This was developed and kindly shared with us by Gail Bromiley of DeBakey H.S. in Houston, TX. Gail also provides a key to facilitate your discussion of the site and worksheet.

14. Another optional extension: Assign different parts of the 11 page article "Origin of Whales..." (by Ray Sutera) to different students or student teams. Article is available from the PDF materials page. You could even cut it into sections and give each of the nine sections to a different team. Each team totally immerses in its assigned portion and gathers whatever details it can find (internet) to gain full understanding. Teams report back to class, so that everyone realizes that there are multiple independent lines of evidence all pointing to the evolution of whales from certain terrestrial mammals.

15. If time allows, consider distributing the Whale Evolution Data Table, (available from the PDF materials page) and making numerous resources available (websites, articles, etc.) from which students (or teams) can gather information to complete the table. For a key to the table, contact the webmaster.

16. SPECIAL NOTE: If students challenge the idea of macroevolution (origin of a major group from a different major group), Click here to help them explore many of the different lines of evidence pointing to speciation and macroevolution. For a very useful diagram to help students see how macroevolution relates to microevolution, see the Macroevolution Diagram below.

17. How ancient whales lost their legs, got sleek and conquered the oceans: an Evo-Devo solution. (Posted 1 June 2006)
Read this beautiful blending of paleontology, developmental morphology and the blossoming field of evolutionary developmental biology, and find an excellent example of MILEs: multiple independent lines of evidence, confirming the tetrapod origin of whales. A recent study, using porpoise embryos, has revealed how a mutation in the gene for "sonic hedgehog" (shh), a developmental signaling protein necessary for normal limb development, resulted in the loss of the hind limbs of early whales about 35 million years ago. Fossils have shown the gradual reduction in hind limbs prior to that time, over a 15 million year period, but the shh mutation appears to be the final step bringing the full sleekness that we see in cetaceans today. Very clever science.

This 2006 PNAS report, by whale evolution veteran JGM Thewissen, et al., is nicely summarized (with full citation to the original) by PZ Myers on the Pharyngula site at: http://scienceblogs.com/pharyngula/2006/05/no_genes_were_lost_in_the_maki.php
It includes an excellent illustrated cladogram (from the original) that shows the gradual hind limb reduction in ancestral whales, and the corresponding changes in regulatory genes.

My thanks to John Pastor, University of Florida for his help in gathering this information.

18. Another teacher's experience, and suggested modification:
I've used the fossil hunt for a few years in my courses and modified it so that it is a little more student centered --I cut the reading part up into segments and place them into separate envelopes so that each student in a group of four has to read one or two of the scenarios and then the group follows the directions. Allows the college students to work at their own pace more and delve into some areas further without constant interuption from the teacher--may be less effective for younger kids. My pre-service teachers like the lesson and a few have taken it into their own classrooms and used it also.
Dr. Christine Lotter
Assistant Professor, Secondary Science Education
Instruction and Teacher Education, SC

19. Still another approach, from another teacher, is to provide each student or team of students with a WORKSHEET (see the pdf handouts page). This more structured approach allows each student/team to progress independently, following the printed narrative and placing the fossils stips as they go. Includes discussion questions. Could be a problem with some teams/students finishing ahead of others (harder to keep class in stiep).

MACROEVOLUTION DIAGRAM: See the Macroevolution Diagram and a page of directions for using that diagram on an overhead projector. This nicely shows how accumulated speciations can eventually form all the groups and subgroups of organisms. It also shows how classification is related to evolution. A very nice colorful version of this can be found on page 32 of that most useful resource: Teaching About Evolution and the Nature of Science, by the National Academy of Sciences (1998) (see our Resources section). A particularly interesting alternative diagram is the one Darwin included in The Origin of Species (chapter IV), the only diagram in that book! His discussion there of that diagram should be required reading for any biology teacher. Darwin's Tree makes a great overhead transparency for discussing his concept of evolution by natural selection, as well as how classification reflects that evolution.

For an excellent tutorial to introduce phylogenetic (evolutionary) trees, see our review of an article in the American Biology Teacher.

 

 

RESOURCES

Books:
Freeman, Scott & Jon C. Herron. 2001. Evolutionary Analysis. Prentice Hall.

Zimmer, Carl. 1998. At the Water's Edge. The Free Press. An excellent, recent treatment of the search for evidence of whale evolution, macroevolution in general, and some of the "behind the scenes" stories of the scientists involved. Highly recommended, for teacher and interested students.

Articles:
Thewissen, J.G.M. et al. 2009. "From Land to Water: the Origin of Whales, Dolphins, and Porpoises." Evcolution: Education & Outreach, v.2, n2, June, 2009.

Thewissen, J.G.M., et al. 2001. "Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls." Nature, 413:217-281 (20 Sep 2001). This report hinges largely on new postcranial fossils of Pakicetus.

de Muizen, Christian. 2001. "Walking with whales." Nature, 413:259-260 (20 Sep 2001). A summary discussion of Thewissen's report.

Gingerich, P.D. et al. 2001. "Origin of Whales from Early Artiodactyls: Hands and Feet of Eocene Protocetidae from Pakistan." Science, 293:2239-2242 (21 Sep). This report hinges largely on new fossils of Rodhocetus.

Rose, Kenneth. 2001. "The Ancestry of Whales." Science, 293:2216-2217. This is a summary of Gingerich's report, and includes a cladogram showing the proposed ancestry.

Sutera, Raymond. 2000. "The Origin of Whales and the Power of Independent Evidence". In Reports of the National Center for Science Education, vol.20, no.5 (Sep/Oct 2000), pp. 33-41. An excellent overview of cetacean evolution, and pointing to several different independent lines of evidence in support of the process. (Mildly critical of creationist veiws). [Copy available at end of lesson]

Gatesy, J.M. et al 1999. "Stability of cladistic relationships between Cetacea an higher-level artiodactyl taxa." Systematic Biology 48(1):6-20.

Nikaido, Masato, et al. 1999. "Phylogenetic relationships among cetartiodactyls based on [DNA] insertions of short and long interspersed elements: Hippopotamuses are the closest extant relatives of whales." Proc. Natl. Acad. Sci. USA, vol.96, pp. 10261-10266.

Thewissen, J.G.M., L. J. Roe, et al. 1996. "Evolution of cetacean osmoregulation." Nature, vol.381, 30 May 1996, pp. 379 380. Study showing oxygen isotope ratios associated with freshwater ingestion vs. seawater ingestion, and whale evolution.

Blackburn, Daniel G. 1995. "Paleontology Meets the Creationist Challenge". Creation/Evolution Issue 36 (July 1995), pp. 30-31 on whale evolution. [Available from NCSE; see website listings below].

Zimmer, Carl. 1995. "Back to the Sea" January 1995 Discover Magazine, pp. 82-84.
Wells, Neil. 1994. Review of Darwinism: Science or Philosophy,. In Creation/Evolution Issue 38 (July 1996), pp. 20-21 on whale evolution, rebuttals to views of Johnson, Behe and Gish. [from NCSE].

Wilford, John N. 1994. "How the Whale Lost Its Legs And Returned to the Sea." In The Science Times Book of Fossils and Evolution, ed. by Nicholas Wade, 1998, The New York Times, pp 143-148.

Gould, Stephen Jay. 1994. "Hooking Leviathan by Its Past". May 1994 Natural History Magazine.

Gingerich, Philip D. 1994. "The Whales of Tehthys". April 1994 Natural History Magazine.

Berta, Annalisa. 1994. "What is a Whale?" Science 14 Jan. 1994 (vol.263, pp. 180-181).

Novacek, Michael. 1993 "Genes tell a new whale tale." 28 January 1993 Nature (vol. 361, pp 298-299.

Landau, Matthew. 1982. "Whales: Can Evolution Account for Them?" Creation/Evolution, Issue X (Fall 1982)., pp. 14-19. [Available from NCSE; see website listings below].

Conrad, Ernest C. 1982. "True Vestigial Structures in Whales and Dolphins." Creation/Evolution, Issue X (Fall 1982), pp. 8-13. [Available from NCSE]. Ref. to hind limb buds in whale embryos, etc.

Web Links:
(if a listed site is not working, please let us know, and try a Google search):
WHALE EVOLUTION
Babinski Blog: Cetacean Evolution (Very thorough, lots of good illustrations)
http://etb-whales.blogspot.com/2012/03/evolution-of-whales-adapted-from.html
Origin of Whales (Science Cover and Article by Phillop Gingerich, et al.,
"From early artiodactyls: hands and feet of Eocene Protcetidae from Pakistan"
http://www-personal.umich.edu/~gingeric/PDFfiles/PDG381_Artiocetus.pdf
"Research on Origin and Early Evolution of Whales" Gingerich, et al.
http://www-personal.umich.edu/~gingeric/PDGwhales/Whales.htm
Whale Evolution: Short video clip (6') in Video #3 of the PBS Evolution Series: with Phil Gingerich and Pakicetus (play online, or purchase this great series of single-concept videos:
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
Transitional Whales <http://www.talkorigins.org/faqs/faq-transitional/part2b.html>
Cetacean Evolution <http://www.ucmp.berkeley.edu/mammal/cetacea/cetacean.html>
Primitive Whales <http://www.enchantedlearning.com/subjects/whales/allabout/Evol.shtml>
dolphin embryo with a hind limb bud! (with kind permission of Hans Thewissen)
Whale nursing: <http://www.seaworld.org/infobooks/KillerWhale/birthkw.html>
Whale hair info: <http://whale.wheelock.edu/archives/ask97/0252.html>
Whale hair info 2: <http://whale.wheelock.edu/archives/ask99/0336.html>

GENERAL EVOLUTION
Evolution on line (WGBH/PBS Evolution Web Site) <http://www.pbs.org/evolution>
NAS (Nat'l Acad. of Sciences): Teaching About Evol. and Nat. of Science. <http://www.nap.edu/readingroom/books/evolution98/evol2.html>
NCSE (National Center for Science Education): <http://www.ncseweb.org> e-mail: ncse@ncseweb.org

GEOLOGIC TIME SCALES (CURRENT)
USGS w/ details <http://vulcan.wr.usgs.gov/Glossary/geo_time_scale.html>
Time Machine (ENSI) <http://www.indiana.edu/~ensiweb/lessons/time.mac.html> (Extensions, Other Resources.)

 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 (lesson conceived 10/8/1997)
2. Edited / Revised for website by L. Flammer 8/31/2001;
updated and extensively revised 11/2002, 12/2007, 2/2009
3. Front painting of Ambulocetus, courtesy of artist Carl Buell.
4. Re-Drawings for graphic pages, courtesy of artist Janet Dreyer
5. See "List of Credits" for original sources of all illustrations used in this lesson.
6. Major revisions, mostly bringing sharp versions of the 6 whale stips + version from Science Kit.


WHALES IN THE MAKING
List of Credits: Sources for Illustrations

ILLUSTRATIONS (all redrawn for this page by Janet Dreyer, Illustrator)
1. Primitive Whales, e.g.: Dorudon, Prozeuglodon,) ~ 36 mya
a. Dorudon atrox: Gingerich and Uhen, 1996
b. Prozeuglodon: Rich et al, 1996
c. Prozeuglodon: Rich et al, 1996

2. Mesonychids (Extinct Land Mammals, with whale-like teeth, e.g. Pachyaena,Sinonyx) ~ 55 mya
a. Pachyaena ossifraga: Gingerich et al, 1994
b. Sinonyx jiashanensis: Zhou et al, 1995
c. Pachyaena: Zimmer/Buell, 1998, p. 157

3. (1983) Pakicetus inachus (skull and teeth only) ~ 50 mya
a.Zimmer/Buell, p. 165
b. Gingerich 1983
c. Zimmer/Buell, p. 203

4. (1990) Basilosaurus isis (hind leg found) ~ 37 mya
a. Thewissen's web site
b. Gingerich, 1990
c. National Academy of Sciences

5. (1994) Rodhocetus kasrani ~ 46 mya
a. Gingerich, 1994
b. Zimmer/Buell, p. 195

6. (1994) Ambulocetus natans ~ 48 mya
a. Thewissen, 1994
b. National Academy of Sciences

SOURCES
- Gingerich, Philip D., et al. 1983. "Origin of Whales in Epicontinental Remnant Seas: New Evidence from the Early Eocene of Pakistan" Science, vol. 220, page 404, 22 April 1983.

- Gingerich, Philip D., et al. 1990. "Hind Limbs of Eocene Basilosaurus: Evidence of Feet in Whales" Science, vol. 249, page155, 13 July 1990.

- Gingerich, Philip D., et al. 1994. "New whale from the Eocene of Pakistan and the origin of cetacean swimming" Nature, vol. 368, page 845, 28 April 1994.

- Gingerich, Philip D. and Mark Uhen. 1996. "Ancalecetus simonsi, a new dorudontine archaeocete from the early late Eocene of Wadi Hitan, Egypt." Contributions from the University of Michigan Museum of Paleontology. 29(13): 359-401.

- National Academy of Sciences. 1998 Teaching About Evolution and the Nature of Science. page 18.

- Rich, Patricia V. et al. 1996. The Fossil Book. Dover Publications, N.Y. p. 564.

- Thewissen, J.G.M., et al. 1994. "Fossil Evidence for the Origin of Aquatic Locomotion in Archaeocete Whales" Science, vol. 263, page 211, 14 January 1994.

- Uhen, Mark web site: <http://www-personal.umich.edu/~uhen/>

- Zhou, X, P. Gingerich & L. Chin. 1995. "Skull of a new Mesonychid from the late Paleocene of China." Journal of Vertebrate Paleontology. 15(2): 387-400.

- Zimmer, Carl; Illustrations by Carl Buell. At The Water's Edge. 1998. The Free Press. [Permission kindly granted by author and illustrator to use any illustrations from this book for ENSI lessons.]

 

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