CAMINALCULES: AN ADVENTURE IN SYSTEMATICS FOR BIOL 102
In the 1960s Joseph Camin, a biologist at the University of Kansas, invented an imaginary group of animals, now known as caminalcules. He created them using pen and ink drawings. He invented a large number of Recent (i.e. still existing) and fossil species. In creating his fossils he used tracing paper overlays to ensure that his fossils evolved in a biologically reasonable manner.
Whatever Camin’s motives for creating these imaginary organisms, caminalcules are ideal for introducing the concepts of classification and phylogeny. Rather than simply being told what the classification and evolutionary history of a group is, you will have to determine it yourself. Because they are imaginary, you won’t have any preconceptions as to how they should be grouped.
This exercise is divided into three parts. For this exercise you may work alone or in a team of two to three students. Each team will turn in its completed exercise for a common grade. See the syllabus for due dates and late penalties.
This activity has been adapted from an exercise published by Dr. R. P. Gendron of Indiana University at Pennsylvania, and is used with permission.
Read Concepts 26.1 through 26.3 in your textbook.
PART 1 – CLASSIFYING THE RECENT SPECIES
For this exercise we will use 14 species of the Recent Caminalcula (Recent is a synonym of Holocene, and refers to modern species). Your goal is to classify these 14 species into a Linnaean hierarchy, assuming that they are the only known members of the Phylum Caminalcula. You will first group the species into appropriate genera, the genera into families, the families into orders, and if necessary, the orders into classes. Obviously, none of the molecular data often used by modern taxonomists are available, and you will have to base your classification on anatomical similarity (i.e., morphology). The assumption that anatomical similarity reflects genetic similarity and evolutionary relationship is often a reasonable one. Indeed, even today, for many real taxa molecular data are not available and classification schemes are still based entirely on anatomical resemblance.
Be aware that in some cases a similarity between two species may not reflect an evolutionary relationship, but rather may be the result of convergent evolution (i.e., an analogy or homoplasy). This occurs when different species independently evolve similar structures in response to similar environmental challenges. For example, in many respects whales superficially resemble fish, but the fact that they have hair, produce milk, and are homeothermic clearly shows that they are mammals, more closely related to camels than to fish.
Examine the 14 Recent caminalcule species (you will use these 14 species again in Exercise II). Note the variety of appendages, shell shapes, coloration pattern, etc. Each species is identified by a randomly-generated number. Compare the caminalcules, noting similarities and differences. On a sheet of paper create a hierarchical classification of the Recent species, using the format in Figure 1. Instead of using letters, as in the example, use the number of each caminalcule species. Remember that Figure 1 is only a hypothetical example, and your classification will look quite different.
Figure 1. Classification format.
Your first step should be to group the species into genera. Remember that species in the same genus should share characteristics not found in any other genera. The caminalcules numbered 19 and 20 are a good example; they are clearly more similar to each other than either is to any of the other living species. Place 19 and 20 in the same genus. After you have erected your genera, use the same procedure to group your genera into families. Again, the different genera within a family should be more similar to each other than they are to genera in other families. Families can be combined into orders and orders into classes. In some cases there may be only a single species in a genus, a single genus in a family, etc. Depending on how you group the species, you might have one or two classes. When you are done you should have a neat and legible version of Figure 1 for your classification.
PART 2 – PHYLOGENETIC ANALYSIS OF THE RECENT SPECIES
Now you will construct a phylogenetic tree of the caminalcules, using your classification from Part 1. You can do this even though the only data you have are the appearance of the 14 Recent caminalcules. Remember that, aside from homoplasy (analogy), we assume that similar structures represent evolutionary relatedness, and that the classification you created in Part 1 is an hypothesis of phylogeny.
For example, assume you have put species A and G into the same genus because you think they evolved from a common ancestor, x. Their part of the phylogenetic tree would look like the diagram in Figure 2. When there are more than two species in a genus you must decide which pair of species shares a common ancestor not shared by the others. In Figure 3, E and K are believed to be more closely related to each other than either is to C. The hypothesis is that E and K have a common ancestor, y, that they do not share with C, while z is the common ancestor of the genus consisting of E, K and C.
Similarly, two genera that more closely resemble each other than they do other genera presumably share a common ancestor.
Figure 2. Species in the same genus. Figure 3. Ancestry within a genus.
Construct a phylogenetic tree (technically called a cladogram) of the caminalcules using your classification from Part 1. Branching must involve only two lines at a time (i.e., it must be dichotomous). The most recent branches should be at the top of the tree, the most ancestral forms at the base. Therefore, all your Recent species will be arranged along the top of the tree, and all ancestors will be hypothetical. When you are finished, make a neat copy of your cladogram.
PART 3 – ESSAY
Choose an order that has at least two families and three genera. For the order and each of its families and genera describe at least one synapomorphy (shared derived characteristic). Explain your choices. Part 3 is to be typed, using Times New Roman font, font size 12, and 1.5 line spacing.
Note on grading Exercise 1 – Classifications and phylogeny in Parts 1 and 2 do not have to be “correct” to receive full credit. Classifications may differ among students even if Part 2 is identical. You will be graded on coming up with a reasonable classification and phylogeny, and how well you defend your conclusions in Part 3. The 50 points for this assignment will be apportioned as follows: Part 1, 12.5; Part 2, 12.5; Part 3, 12.5; Presentation in Parts 1 and 2, and “English” (neatness, spelling, grammar, syntax, typos, paragraph organization) in Part 3, 12.5. All sheets you turn in must be stapled together or points will be deducted. Any unfastened pages with no name on them will be discarded.
14 species of Recent Caminalcules. Numbers are for identification.
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