How to Make a Phylogeny Tree

by Ann LaPan
Evolutionary mutations create variations within species.

Evolutionary mutations create variations within species.

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A phylogeny tree is a written plot that shows how genetic mutations occur. A phylogeny tree is also called an evolutionary tree or a phylogenetic tree. To construct one, evolutionary descent is noted on each branch of the tree, beginning with the earliest mutation. As mutations occur, they are noted on new branches of the tree, which then extend until further mutations occur. The top of the tree may show species that currently exist.

Items you will need

  • Pencil
  • Paper
  • Ruler
  • List of evolutionary mutations of the subject species
Step 1

State the earliest ancestor of the evolution of the species at the bottom-center of your paper. Draw a vertical line up 1 inch to show the trunk of the tree. For example, if you draw a tree of the Phyla, state that name at the root level of the tree.

Step 2

Draw a straight line that branches off the trunk all the way to within 1 inch of the left of the paper, and then draw a vertical line rising from it. This will be the branch where no evolutionary change has occurred. For example, on the Phyla tree, indicate the first species is "unicellular."

Step 3

Continue the vertical line to the top of the page, if no other changes have occurred to this strain of the species during the course of evolution. In the Phyla example, label the top of the branch "protozoans."

Step 4

Draw another branch higher up the trunk of the tree to indicate the next mutation. There will be instances on your tree where a mutation occurs, creating a new creature. That creature's descendants may mutate to form others or may not have any mutations. Label the first mutation near the trunk of the tree.

Step 5

Note the date of the mutation if you have it. It is not necessary to extend the line any longer to indicate the expanse of time, since the purpose of the phylogeny tree is to note the changes, not how long they took to occur.

Step 6

Split the upward moving branch to label the next mutation that occurs from the species created by the last one. In the example of the phyla, bilateral symmetry occurred, and from those creatures that moved in a headfirst direction, a mutation for radial symmetry occurred. At the top of the branch, the species "jellyfish" can be labeled.

Step 7

Continue filling out the splits in genetic mutation. If mutations occurred in more than one branch, indicate them, too. For example, in the Phyla tree, segmentation occurred in both the protosomes branch and the deuterostomes branch producing species of crabs and starfish respectively.

Photo Credits

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