5.5 Phylogeny and Cladistics

What is phylogeny?

Phylogeny is the study of relationships among groups of organism, tracing their lines of descent and shared ancestry

What is an evolutionary tree?

any tree used to show evolutionary relatednes (often simplified.

What are the two types of evolutionary trees?

• Cladogram = a tree divided into easily distinguishable groups, (does not show passage of time)

• Phylogenetic tree = a tree used to quantify passage of time

What is a clade

A clade is a common ancestor and all its descendants

• decided by genes and/or protein sequences

What is an Outgroup

a more distantly related group that diverged prior to the clade in question

What is the root

the base of the evolutionary tree

what is a branch

a line extending from the tree

• must be labeled with defining characteristics

What are the nodes

where branches touch indicating a common ancestor

what is a terminal branch

the outermost branches

what is a sister group

two organisms that share a most recent common ancestor

what are cladistics

an approach to biological classification in which organisms are arranged into clades based on hypothesis of most recent ancestry

How is cladistics helpful

• help us predict characteristics of new, undiscovered, and even extinct organisms

• allows us to re-evaluate the current system of classification to see what we may need to change