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Plant Phylogeny Lab
 

Plant Phylogeny Lab

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    Plant Phylogeny Lab Plant Phylogeny Lab Document Transcript

    • I N Q U I RY & I N V E S T I G AT I O N Hands-On in the Non-Laboratory Classroom Reconstructing Plant Phylogenies Using Morphological Characters S. L U K E F LO RY E L L A L. I N G R A M B R I T T J. H E I D I N G E R TA M M Y T I N T J E R Appendix. The following pages are the Appendix for this article that ran in the November/December 2005 issue of The American Biology Teacher: Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2 Discussion Leader Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3 Pre-Activity Worksheet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4 Plant Phylogeny (Student Worksheet) . . . . . . . . . . . . . . . . . . . . . . A5 Molecular Phylogeny . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A6 Individual Accountability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A7 Plant Photographs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A8 RECONSTRUCTING PLANT PHYLOGENIES A1
    • Lesson Plan: Plant Phylogeny General Description This activity is designed to introduce students to phylogenetic reconstruction using morphological char- acters. Students will examine live potted plants and/or photographs and create a hypothesis regarding their relationships. Objectives The student will: 1. Choose morphological characters and character states useful in phylogenetic reconstruction. 2. Use a character state matrix to reconstruct a phylogeny based on parsimony. 3. Determine if characters are ancestral or derived, or homologous or analogous based on their phy- logenetic hypothesis. 4. Compare and contrast phylogenies based on different characters and data types. 5. Determine probable evolutionary relationships based on their phylogenetic reconstruction. Concepts parsimony, ancestral and derived character states, phylogeny, sister groups Time Approximately 50 minutes Materials 7 live potted plants with accompanying pictures (or pictures only) Molecular Phylogeny overhead 2-page Group Worksheet Refer to the following website for more information on Angiosperm phylogenies: http://www.mobot.org/MOBOT/Research/APweb/welcome.html A2 THE AMERICAN BIOLOGY TEACHER, VOLUME 67, NO. 9, NOVEMBER/DECEMBER 2005
    • Discussion Leader Instructions: Plant Phylogeny 1. [20 minutes] Break students into groups of four and hand out the “Group Discussion” worksheet. Students should then follow the handout to guide their exploration of characters and character states for the live plants. During their group discussion, one student should be in charge of tak- ing notes on what they discuss to help guide the presentation of their results. Each group should prepare a short presentation on the phylogeny they constructed and one student should be pre- pared to present their phylogeny to the class. When completed, have each team draw their phy- logeny on the board. 2. [10 minutes] Have the groups present their ideas to the entire class, particularly regarding the 3 most important characters that determine the arrangement of the phylogeny they created. 3. [10 minutes] Lead a class discussion of the groups’ results: a. As a class, have the students compare and contrast the characters they used to create their phylogenies—did they use similar characters? Which were the most common? Does one char- acter significantly influence the phylogeny of any group? b. Have students compare and contrast the phylogenies the groups came up with—are they the same? How do they differ? Do they get the same relationships between some plants, but dif- ferent relationships for others? What characters do they think are responsible for the differ- ences in the phylogenies? 4. [5 minutes] Put up the overhead of the molecular phylogeny of the same plants and discuss as a class one or two of the following questions: a. How is the molecular phylogeny the same and different from what the class came up with based on morphology? b. Why might there be these differences? (Remember: this phylogeny is based on molecular data, not on morphological data) c. Could the same relationship be reached with morphology, if it wasn’t already? d. What are some limitations of simply looking at live plants for this activity? e. Using the molecular phylogeny, can the students determine where changes in some of the characters occurred? 5. [5 minutes] If required, have students complete the Individual Accountability questions. RECONSTRUCTING PLANT PHYLOGENIES A3
    • Pre-Activity Worksheet: Plant Phylogeny General Description In the activity you will do this week during your learning/discussion group, you will be learning how evolutionary biologists investigate relationships among organisms, and you will create your own hypothesis of evolutionary rela- tionships in a group of plants. In order to be prepared for this activity, complete this worksheet. Reading Browse the “Phylogeny and Systematics” chapter in Campbell & Reece’s Biology (6th ed). Pay particular attention to figures 25.9, 25.11, 25.12, and 25.15. Read carefully pages 494-502. Definitions Write a definition of the following words. Use your text, textbook glossary, and your previous knowledge to create the best definition possible. Remember to connect your definitions to phylogenies. 1) cladistics 2) parsimony 3) derived character 4) outgroup 5) systematics 6) character state Questions Answer the following questions. You will explore your answers to these questions in-depth during learning/discus- sion group. To practice looking at and understanding characters and character states of plants, visit any campus or greenhouse location with many different species of plants, either by yourself or with a classmate. 1. Find two plants that differ morphologically and list 10 characters. Use the back of this page. Record the species you are examining. 2. Determine and record the character states for these characters for both plants. 3. Does there need to be two character lists? Why or why not? 4. Does there need to be two character state lists? Why or why not? A4 THE AMERICAN BIOLOGY TEACHER, VOLUME 67, NO. 9, NOVEMBER/DECEMBER 2005
    • Plant Phylogeny This activity is designed to allow you to explore how biologists create phylogenies to understand the relationship among organisms and the evolution of various characters. In this exercise you will create a phylogeny using the mor- phology of several plant species. Examine the live potted plants closely. To determine how these plants are related to one another, examine the morphological similarities and differences among the plant species. First consider the four characters with two character states from the table below. For exam- ple, are stems present? In this example, the two character states are absent = 0 or present = 1 (see below). Next, think of at least three additional characters with two character states as a group and add these to the table below. Remember you want to choose characters that will allow you to determine which species are more closely related to one another. C H A R AC T E R A NC E S T R A L S TAT E ( 0 ) D E R I V E D S TAT E ( 1 ) stems absent present flowers absent present at some time number of petals few or none many divided leaves not divided divided Your next step is to assess the states of all of these characters in the potted plants. To do this, examine the plants closely and decide which character state each possess for the characters you chose and fill in the table below. List your characters in the left column. One example is shown. CHARACTER OUTGROUP PLANT 1 PLANT 2 PLANT 3 PLANT 4 PLANT 5 PLANT 6 Presence of Petals 0 0 1 0 1 1 0 Now, using what you have learned about the principle of parsimony and the building of phylogenies, create your hypothesis of the relationships among these organisms. Indicate on your phylogeny the likely places where charac- ters changed from one state to the other. To begin, the outgroup moss is the most ancestral of the plants you have been given. This phylogeny is what you will present to the class, so make it easy to read. Use additional pages as nec- essary. RECONSTRUCTING PLANT PHYLOGENIES A5
    • Molecular Phylogeny Outgroup Plant 1 Plant 6 Plant 5 Plant 3 Plant 4 Plant 2 (moss) (fern) (cycad) (orchid) (palm) (impatiens) (cotton) A6 THE AMERICAN BIOLOGY TEACHER, VOLUME 67, NO. 9, NOVEMBER/DECEMBER 2005
    • Individual Accountability: Plant Phylogeny Demonstrate your new understanding of phylogenies by answering the following questions. In both cases, defend your answer in four or five sentences. 1. Compare and contrast the characters used by different groups. Are some easier to score? Are some more helpful when creating the phylogenies? 2. Why are phylogenies useful to scientists? RECONSTRUCTING PLANT PHYLOGENIES A7
    • Photographs: Outgroup – Moss A8 THE AMERICAN BIOLOGY TEACHER, VOLUME 67, NO. 9, NOVEMBER/DECEMBER 2005
    • Photographs: Plant 1 – Fern RECONSTRUCTING PLANT PHYLOGENIES A9
    • Photographs: Plant 2 – Cotton A10 THE AMERICAN BIOLOGY TEACHER, VOLUME 67, NO. 9, NOVEMBER/DECEMBER 2005
    • Photographs: Plant 3 – Palm RECONSTRUCTING PLANT PHYLOGENIES A11
    • Photographs: Plant 4 – Impatiens A12 THE AMERICAN BIOLOGY TEACHER, VOLUME 67, NO. 9, NOVEMBER/DECEMBER 2005
    • Photographs: Plant 5 – Orchid RECONSTRUCTING PLANT PHYLOGENIES A13
    • Photographs: Plant 6 – Cycad A14 THE AMERICAN BIOLOGY TEACHER, VOLUME 67, NO. 9, NOVEMBER/DECEMBER 2005