The Tree of Life

 Phylogenetic Trees

Hi class! Today we are going to be learning about phylogenetic trees.

 

A phylogenetic tree is a graphic tool that links together living creatures and can show the relatedness of these organisms. It depicts the history of the evolution of a group of species from a common ancestor.

This tool is called a tree because of the linkage of the linage (how the organism relates to common ancestors) is called branching, and because the organism at the end of a branch is considered a leaf.

Essentially this tool is giving you a visual map of the evolution of groups of species.

 

These phylogenetic trees can be broken into two separate groups.

One group is called a monophyletic. These groups would be considered more closely related to each other because it contains all descendant species from a single common ancestor.

This graphic depicts a lineage of Eevees (disclaimer: Pokemon evolution is not the same as actual evolution, I am simply using my favorite Pokemon to help demonstrate these examples). In this, you can see that all of the descendants trace back to one single common ancestor. This is how you know it is considered a monophyletic group.

 

The other group is called paraphyletic. This group is similar to monophyletic groups in the sense that you are looking at the lineage from a common ancestor. However, it differs because not all of the species that have descended from this ancestor are shown.

This graphic also depicts a lineage of Eevees. In this one make sure to follow along with the purple highlight. You can see the single common ancestor and how it branches into species. However, it also shows that we are excluding one of the species from the illustration. When you excluded one or more species/organisms from a phyletic tree that you are interpreting that is what makes the group paraphyletic.