Materials Included In Kit

Additional Materials Required

Safety Precautions

Students should use special care when cutting with scissors. Follow all other normal laboratory safety rules.

Disposal

Model phylogenetic trees might be saved from year to year for comparison.

Teacher Tips

• Enough materials are provided in this kit for 30 students working in pairs or 15 groups of students. All materials are reusable. For this particular activity, however, larger groups might be advantageous. Placement of the Caminalcules on the chart is not an easy task and more heads might prove to be better.

• This activity will require at least three class periods and perhaps more depending upon the amount of interest, discussion, and number of group presentations. One class period (with discussion) will be required for Part I. Part II of the activity will likely require two class periods at a minimum. A fourth or fifth class period might be required for discussion and presentations.
• After students complete their classification of the living Caminalcules in Part I of the activity, you will want to lead a discussion of their classification schemes. You may want to form a consensus so that all groups start with the same first line in Part II of their phylogenetic tree. This is a judgment call that is likely to be dictated by the student groups and your goals for the activity. Most students will likely classify 2, 3, 4, 12 and 22 together. A common mistake might be to put 3 and 12 in a genus by themselves because they both have claws. This is an excellent opportunity to note that classification should be based on all available characteristics. When color pattern, body shape, presence of elbows and head ornamentation are considered, they will likely decide that 3 and 4 belong in one group (genus) and that 2, 12 and 22 belong in another. Caminalcule 3 and 12 provide an excellent opportunity to discuss convergent evolution.
• The whole issue of “lumpers” and “splitters” will arise in this part of the activity. To err on the side of “splitting” for this particular activity is probably preferred. “Lumping” makes the phylogenetic tree more difficult.
• The creation of the phylogenetic tree is not an easy or quick task if taken seriously. Provide ample time for students to work, think and debate the placement of organisms and their possible relationships.
• The possible answers provided for your use are not meant to imply a “right” answer. Similarities should emerge among various schemes but minor differences are to be expected.
• If students work on the phylogenetic tree from one day to another, have them record their tentative placements on their charts by writing the Caminalcule number in pencil on the timelines. Then in the next class period they can quickly replace the pictures on the chart before finalizing their placements.
• Clever placement of the Caminalcule pictures on the chart makes drawing the lines of the tree easier. Encourage students to “plan ahead.”

Sample Data

Part I. Classification of Living Caminalcules

Show your classification scheme by dividing each line in the chart into the appropriate number of sections for the Orders (O₁, O₂...), Families (F₁, F₂...), Genus (G₁, G₂...) and Species (1–14).

Part II. Examining the Fossil Record

Answers to Questions

Part II. Examining the Fossil Record

After examining various phylogenetic trees, answer these questions.

1. How were the various phylogenetic trees similar?
   

   Answers will vary. All should start with the common ancestor at #73 on the 19 million year line and end with connections to the 14 living Caminalcules.
   

2. What forces may have caused various changes in the Caminalcules population over time?
   

   Students could speculate many possibilities (e.g., movement, isolation, disease, natural disasters, mutations).
   

3. What might a newfound fossil do to your phylogenetic tree?
   

   It might change it a lot or a little depending upon its age and possible placement in the phylogenetic tree.
   

4. What other information about Caminalcules might help in reshaping a phylogenetic tree?
   

   Any data about habitats, behavior, genetic makeup or any other physiological characteristics.
   

5. What might explain any “dead-ends” in the Caminalcules phylogenetic tree?
   

   Changes in environmental conditions could cause the sudden death of a specific population.

Teacher Handouts

10331_Teacher1.pdf

References

A special thanks to the late Joseph Camin for creating the Caminalcules and to the following individuals for granting permission for the reproduction of the Caminalcules for this activity: Dr. Robert Sokal, who first published the Caminalcules, and Dr. Richard Olmstead, editor of Systematic Biology.

Gendron, R. P. (2000). The Classification and Evolution of Caminalcules. The American Biology Teacher, 62 (8), 570–576.

Sokal, R. R. (1983). A Phylogenetic Analysis of the Caminalcules. Systematic Zoology, 32, 159–184.

Introduction

Create a classification scheme for fourteen fictitious organisms called Caminalcules. Once a classification scheme has been proposed a phylogenetic tree can be created using numerous additional Caminalcules from the fossil record.

Concepts

• Classification

• Fossil record
• Phylogenetic tree
• Taxonomy

Background

The number and different kinds of organisms in the world is mind-boggling. Keeping track of all the various species and trying to identify relationships among them presents a great challenge. Imagine trying to identify relationships among organisms as diverse as giraffes, microbes, fish and oak trees. Trying to sort out one species, such as ants, is a real challenge. Biologists like to group “like things” with “like things,” that is, to put them into logical categories. The question becomes—what logic, whose logic and what is logical? The field of biology that identifies and classifies organisms into categories is called taxonomy.

Taxonomists analyze shared characteristics to determine possible relationships among organisms. As more and more information is collected about various species, new relationships and categories often emerge. The field of taxonomy is a changing one and one that often results in serious disagreements.

The general classification system that biologists use today is based upon a system developed in the mid-1700s by a Swedish biologist named Carl von Linnaeus. He established a system of groups he called taxa (singular taxon). Each taxon is a category into which related organisms are placed. Thus, the name taxonomy. Linnaeus ranked taxa starting with the broadest, most general groups and proceeding down to the smallest, most specific groups.

The broadest, most general group was called a kingdom. Kingdoms are divided into groups called phyla. Within each phylum there are groups called classes. Classes are then divided into orders. Orders are divided into families. Families are divided into genera. Finally genera are divided into species.

Linnaeus proposed further to use a binomial nomenclature system for naming each species. First there is the genus name, which is followed by the species name. The genus name is capitalized and the species name is not. Both words of the name are printed in italics or underlined. For example, the biological name for the animal we commonly call the lion is Panthera leo. The tiger is Panthera tigris while the house cat is Felis catus.

The complete classification of the three cats would be as shown in Table 1.

Which of these cats are most closely related to each other?

With Caminalcules, as with real organisms, physical similarities are usually a good indicator of common ancestry. If two species are in the same genus, it implies that these species share a common ancestor not shared by other genera. Biologists use the ability to interbreed and produce viable offspring as the criteria for defining a specific genus. In creating a “map” of past genetic and generational relationships, it is assumed that previous common ancestors could produce genetically viable offspring to continue into the next generation. Such “maps” showing possible past relationships is referred to as a phylogenetic tree. See the specific example diagrammed in Figure 1.

When a genus is made up of three (or more) species, a taxonomist must try to decide which of the species share a common ancestor not shared by the others. The segment of a phylogenetic tree, shown in Figure 1, indicates that Species 26 and 3 are judged to be more closely related to each other than either is to Species 29. It is then hypothesized that 26 and 3 have a common ancestor, A, that is not directly shared by species 29. But, since 26, 3 and 29 are all of the same genus, they share a common ancestor, B.

Materials

Safety Precautions

Use special care when cutting with scissors. Follow all other normal laboratory safety rules.

Procedure

Part I. Classification of Living Caminalcules

1. Secure a sheet containing drawings of the current living Caminalcules. Cut along the dotted lines to separate the 14 living Caminalcules.
2. Spread the Caminalcule drawings on a work surface and examine each Caminalcule carefully. Study the anatomy of each Caminalcule. Discuss the common anatomical features and place the Caminalcules into logical groups.
3. Assume that Caminalcule is a Class name. Create groups for the 14 Caminalcules for Orders, Families, Genus, and Species. Use O₁, O₂... etc. for the Order names. Use F₁, F₂... etc. for the Family names. Use G₁, G₂... etc. for the Genus names. Use the numbers of the Caminalcules as the Species name.
4. Record your classification scheme by filling in the chart on Part I of the Caminalcules Worksheet. (It will look something like the cat classifications chart in the Background section.)
5. Once all groups have completed their classification schemes, conduct a class discussion and compare the various classification schemes. Consider the various logics used by different groups.

Part II. Examining the Fossil Record

1. Secure the sheets containing the drawings of the fossil Caminalcules. Cut along the dotted lines to separate the fossil Caminalcules.
2. Use a meter stick and a permanent marking pen to make a time scale down the left side of the large chart paper as shown in Figure 2. Allow at least 1¾" for each mark on the time scale. A light pencil line can be drawn across the chart at each million year line to help line up the organisms at each generation.

3. Place the pictures of the living Caminalcules across the large chart on the zero line (present time) keeping them in the order as written on the species line of the chart in Part I on the Caminalcules Worksheet. Keep the most closely related Caminalcules together on the zero line. (If there is an agreed upon order from the class discussion of Part I, use that order.) Tape or glue the living Caminalcules in order across the top of the chart on the zero line.
4. Notice that each fossil Caminalcule has a number as its name. In addition, there is another number in parentheses. This number indicates the age of the fossil in millions of years. Organize all the fossil Caminalcules by age.
5. Examine the fossil Caminalcules that are one million years old. Examine each one individually and determine which one(s) of the living Caminalcules it seems to most closely resemble. (Notice that some are actually identical to the current living organism.) Place each one-million-year-old fossil on the one million line of the large chart directly beneath the Caminalcule on the zero line it most closely resembles.
6. Continue this procedure through each age from 1–19 million years down the large chart. Continue to place the ancestors on the line beneath the younger Caminalcules above. Review Figure 1 in the Background section and look for patterns similar to those in Figure 1. Look for what might be common ancestors and possible connections between common ancestors.
7. As patterns develop that seem logical and defensible, tape or glue the Caminalcules in place and use a permanent marker to connect the pictures to reflect the possible phylogenetic relationship between various Caminalcules. Continue to search for patterns and draw lines to connect ancestors one to another until all the Caminalcules have been connected to the oldest known fossil #73.
8. When all groups have been connected, a phylogenetic tree for the Caminalcules will be formed.
9. Display all the various phylogenetic trees that have been created and take turns explaining the trends that seemed to emerge. Consider the amount of similarity and differences that exists among various phylogenetic trees. Which patterns are most defensible? Is there an absolute answer?
10. Answer the questions in Part II of the Caminalcules Worksheet.

Student Worksheet PDF

10331_Student1.pdf