Biology > STUDY GUIDE > How to Build a Cladogram.>Building Cladograms Practice WS 2020/Harvard University (All)

How to Build a Cladogram.>Building Cladograms Practice WS 2020/Harvard University

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How to Build a Cladogram. Background: TOC# Cladograms are diagrams that we use to show phylogenies. A phylogeny is a hypothesized evolutionary history between species that takes into account thing ... s such as physical traits, biochemical traits, and fossil records. To build a cladogram one must take into account all of these traits and compare them among organisms. Building a cladogram can seem challenging at first, but following a few simple steps can be very beneficial. Watch the following, short video, read the directions, and then practice building some cladograms. Video: http://ccl.northwestern.edu/simevolution/obonu/cladograms/Open-This-File.swf Instructions: There are two steps that will help you build a cladogram. Step One “The Chart”: 1. First, you need to make a “characteristics chart” the helps you analyze which characteristics each specieshas. Fill in a “x” for yes it has the trait and “o” for “no” for each of the organisms below. 2. Then you count how many times you wrote yes for each characteristic. Those characteristics with a large number of “yeses” are more ancestral characteristics because they are shared by many. Those traits with fewer yeses, are shared derived characters, or derived characters and have evolved later. Chart Example: Backbone Legs Hair Earthworm O O O Fish X O O Lizard X X O Human X X X “yes count” 3 2 1 Step Two “The Venn Diagram”: This step will help you to learn to build Cladograms, but once you figure it out, you may not always need to do this step. 1. Draw a multi-cicular Venn diagram. You will need as many circles as there are characters. 2. Start with the character that is shared by all the taxa on the outside. (you will want to make this a large circle.) 3. Inside each box, write the species that have only that set of characters. 4. On the outside of the Venn Diagram, write the outgrB [Show More]

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