F23 Lab Cladistics Handout-1 UPDATED

GEOL 207: Dinosaur World Name: _____________________________ Lab Section: 200 500 501 502 503 504 505 Cladistics Objectives • To know how to read a cladogram and understand the terminology used to interpret evolutionary relationships among organisms. • To be familiar with using a data matrix to choose appropriate criteria that will allow you to construct a cladogram • To practice constructing cladograms and forming hypotheses about evolutionary relationships among organisms. Part I: Understanding a Cladogram Exercise 1: Use the cladogram in Figure 1 to complete the chart by determining which taxa (organismal group) have the characters listed in the left column. Place an ‘X’ in the corresponding box in the data matrix if the trait is present; if the trait is absent, then leave the box blank. (4 pts) Figure 1. Cladogram of animal evolution. Table 1. Data matrix of animal evolution shared derived characters.

Porifera Cnidaria Platy helminthes Mollusca Annelida Arthropoda Echino dermata Hemi chordata Chordata Notochord X Pharyngeal Slits X X Complete gut X X X Molting X True Segmentation X X Schizocoel Embryo development X X X Spiral cleavage X X X X Bilateral Symmetry X X X X X X X Gastrulation X X X X X X X X Collagen X X X X X X X X X A. Describe how the pattern in the chart reflects the pattern of the cladogram. (2 pts) Shared traits that crocodilians and birds share.

snakes D. Which organismal groups are members of Tetrapoda? (1 pt) Mammals, snakes, and crocs. E. Tetrapoda is the sister taxon to whom? Hint: You may want to draw a more simplified cladogram. (1 pt) Sharks F. Are “mammals” more closely related to “sharks” or Reptilia? Why? (1 pt) Reptilia due to having more derived traits and being near the cladogram. Part II: Constructing a Cladogram. In each of the following exercises, begin by generating a presence/absence character matrix. List each organism in the first column. In each numbered column, fill in a character you decide is important in your group. (Hint: our first character should be shared by all your organisms.) Next, for each organism that has a character 1, put an X in the space below character 1. Repeat for each character. You may or may not need to add more columns or rows to your table. Once you have completed your data matrix, interpret the data to construct a cladogram to visually represent your data set. Exercise 2 : You are chief astrozoologist on a Mars mission. After prospecting for several days, you assemble a collection of life forms. It is now your job to determine the relationships between these organisms. Use the list of characters given with the matrix below. You decide Oliver should be your outgroup because it appears to be the least specialized, and therefore most primitive. Fill in the matrix. Use “0” to represent the primitive state, as possessed by Oliver. “1” indicates a derived state. (4 pts)

Oliver Groucho Zeppo Chico Harpo 1. Eyes 0 0 0 0 0 2. Mouth 0 0 0 0 0 3. Tentacles 1 1 1 1 4. Horns 1 1 1 5. Pinchers 1 1 6. Legs 1 7. Teeth 1 1 1 Construct a cladogram based upon your matrix. Map all your characters. How many steps are there on your tree? (For each taxon, the number of steps is the number of trait appearances or trait reversals or losses that separate that taxon from the ancestor. On the simple cladogram below, 2 steps separate Zeppo from the ancestral state – don’t count the trait that appears in every member of this group) Should you count characters 1 and 2? Why or why not? (4 pts) Yes, because all organisms have some trait or formation of an eye and mouth.

Ceratosaur X X X X Therizionsau r X X X X X Oviraptor X X X X X X 3B. Now that you have completed the character matrix, transfer each organism onto a cladogram, using the characters as “nodes.” (4 pts)

3C. Briefly describe the evolutionary relationship between modern crocodiles and modern birds, using your cladogram as a guide. (4 pts)

3E. What issues arise with the discovery of new species and finding their placement in evolutionary history? (2 pts) Issues of relationships and their placement in evolutionary history would complicate which will lead to further confusion within different species or organisms regarding their features on cladograms.