 Phylogenetic trees and Cladograms are hypotheses. The only guarantee is that they will change as we gather and analyze more data. From Young and Strode (2009) Why Evolution Works Evolutionary Tree Diagrams

 Cladograms: organize taxa into clades that share derived characteristics that have evolved since divergence from common ancestors.

Clarifying Cladograms  Nodes represent common ancestors.  Species with the more recent common ancestor are considered more closely related.  With a partner, work through the “Basic Tree Thinking Assessment” together.

Fig a,b, p.312 Character Table

Fig a,b, p.312 Character Table Based on the shared characteristics in the diagram above, build a cladogram of the most likely evolutionary history of these organisms.

Fig c, p.313

Fig d, p.313

Fig e, p.313

Fig f, p.313

Fig g1, p.313

19.2 Comparing Body Form and Function: Divergent Evolution  Building trees begins with comparisons of body form and structures (morphology).  Structures with similar morphology reflect shared ancestry. The structures are homologous to each other.  How have they come to be different?

19.2 Comparing Body Form and Function: Convergent Evolution  Structures with similar function do not necessarily reflect shared ancestry. The structures are analogous to each other.

19.4 Comparing DNA and Proteins using Molecular Clocks and Turning Data into Trees  Accumulation of neutral changes in DNA bases can be used to determine time since divergence.  Proteins can also be compared between species and used to establish evolutionary relationships.

 Certain genes are conserved among species more often because of the importance of their functions Comparing DNA and Proteins using Molecular Clocks and Turning Data into Trees A version of the Pax6 gene, responsible for proper development of the eye, can found in mice, fruit flies, and humans… it has even been swapped between species while still functioning!

Now Let’s Build a Cladogram  Using the information provided by your teacher, construct a cladogram that will show the relationship between a chimpanzee, hagfish, perch, pigeon, lizard, salamander, crocodile, and mouse.